Here’s astronaut Christina Koch looking back at Earth, out the window of the Orion spacecraft – aka Integrity – on its way to the moon during the Artemis 2 mission. The Artemis Accords — a set of guidelines for the exploration of space, with a focus on the moon — are named after the Artemis program. Image via NASA.
In 2020, NASA and the U.S. Department of State led an effort to establish guidelines for human expansion into space. Working with international partners, they came up with the Artemis Accords. NASA describes the accords as:
… a common set of principles to enhance the governance of the civil exploration and use of outer space.
As of late September 2026, 74 countries have signed the Artemis Accords. There are some notable exceptions, including Russia and China.
While the rules are for space in general, they are largely focused on humans’ expansion onto the moon. Thus, they are named for NASA’s Artemis program, which currently aims to have humans standing on the moon again in early 2028.
What are the Artemis Accords?
The Artemis Accords are a set of nonbinding principles for how countries should cooperate in space. The accords build on the 1967 Outer Space Treaty. NASA focuses on a number of key areas, including:
peaceful purposes
transparency
interoperability
emergency assistance
registration of space objects
release of scientific data
preserving outer space heritage
space resources
deconfliction of space activities
orbital debris
So, for example, the accords call for protecting historic sites such as the Apollo landing sites. They also support the use of space resources, such as lunar water or asteroid materials, provided those activities comply with international law.
Humanity suddenly has many plans for expanding into space. And it’s not just countries, but private companies with plans as well. So the intention here is to make space safer and more cooperative.
For example, if two nations are operating in the same area of the moon, the accords call for them to share information and coordinate their activities to avoid harmful interference. Temporary safety zones can help accomplish that without claiming ownership of lunar territory.
The accords don’t replace the Outer Space Treaty or create a new international space law. Instead, they just provide a common framework for putting responsible practices into action. As NASA puts it, the goal is a “safe, peaceful and prosperous future in space.”
The Artemis Accords are a set of guidelines for exploration of space with a focus on the moon. NASA named the accords after its Artemis program, which seeks to return people to the moon’s surface and establish a base. Image via NASA.
Questions surrounding the Artemis Accords
There are criticisms and questions surrounding the Artemis Accords. For one, the accords aren’t a binding law but set of agreements. Plus, the Artemis Accords don’t regulate private companies directly. As in, no private companies are signing the accords. Instead, countries sign the accords and are responsible for ensuring that companies operating under their jurisdiction follow the rules.
So, who gets to make the rules for space? The United States is doing much of the steering on the accords. But should it be an international organization, such as the United Nations? The UN Committee on the Peaceful Uses of Outer Space is already working on possible international principles governing space-resource activities. Some delegations at the United Nations have argued that developing countries should not be left behind or excluded from the benefits of space exploration.
A second question is on who gets access to valuable lunar resources. How should those resources be governed? The UN discussions have included calls for rules addressing issues such as sustainability, access, benefit sharing and the rights of countries without the ability to conduct space-resource missions themselves.
Finally, there is the idea of safety zones. The accords allow temporary zones around lunar operations to prevent interference. But the Outer Space Treaty says no country can claim sovereignty over the moon or appropriate it through occupation or use. And couldn’t some countries make a temporary zone that eventually functions like a territorial claim?
While some framework for cooperation in space is necessary, it seems hammering out the details will be a debate for years to come.
The Shackleton crater on the moon with an elevation analysis (left) and shaded relief (right). This 12.5-mile-diameter (21-km-diameter) crater near the south pole is in permanent shadow. Image via NASA.
Bottom line: The Artemis Accords are a set guidelines for peaceful space exploration. But questions remain about who makes the rules and controls space resources.
Here’s astronaut Christina Koch looking back at Earth, out the window of the Orion spacecraft – aka Integrity – on its way to the moon during the Artemis 2 mission. The Artemis Accords — a set of guidelines for the exploration of space, with a focus on the moon — are named after the Artemis program. Image via NASA.
In 2020, NASA and the U.S. Department of State led an effort to establish guidelines for human expansion into space. Working with international partners, they came up with the Artemis Accords. NASA describes the accords as:
… a common set of principles to enhance the governance of the civil exploration and use of outer space.
As of late September 2026, 74 countries have signed the Artemis Accords. There are some notable exceptions, including Russia and China.
While the rules are for space in general, they are largely focused on humans’ expansion onto the moon. Thus, they are named for NASA’s Artemis program, which currently aims to have humans standing on the moon again in early 2028.
What are the Artemis Accords?
The Artemis Accords are a set of nonbinding principles for how countries should cooperate in space. The accords build on the 1967 Outer Space Treaty. NASA focuses on a number of key areas, including:
peaceful purposes
transparency
interoperability
emergency assistance
registration of space objects
release of scientific data
preserving outer space heritage
space resources
deconfliction of space activities
orbital debris
So, for example, the accords call for protecting historic sites such as the Apollo landing sites. They also support the use of space resources, such as lunar water or asteroid materials, provided those activities comply with international law.
Humanity suddenly has many plans for expanding into space. And it’s not just countries, but private companies with plans as well. So the intention here is to make space safer and more cooperative.
For example, if two nations are operating in the same area of the moon, the accords call for them to share information and coordinate their activities to avoid harmful interference. Temporary safety zones can help accomplish that without claiming ownership of lunar territory.
The accords don’t replace the Outer Space Treaty or create a new international space law. Instead, they just provide a common framework for putting responsible practices into action. As NASA puts it, the goal is a “safe, peaceful and prosperous future in space.”
The Artemis Accords are a set of guidelines for exploration of space with a focus on the moon. NASA named the accords after its Artemis program, which seeks to return people to the moon’s surface and establish a base. Image via NASA.
Questions surrounding the Artemis Accords
There are criticisms and questions surrounding the Artemis Accords. For one, the accords aren’t a binding law but set of agreements. Plus, the Artemis Accords don’t regulate private companies directly. As in, no private companies are signing the accords. Instead, countries sign the accords and are responsible for ensuring that companies operating under their jurisdiction follow the rules.
So, who gets to make the rules for space? The United States is doing much of the steering on the accords. But should it be an international organization, such as the United Nations? The UN Committee on the Peaceful Uses of Outer Space is already working on possible international principles governing space-resource activities. Some delegations at the United Nations have argued that developing countries should not be left behind or excluded from the benefits of space exploration.
A second question is on who gets access to valuable lunar resources. How should those resources be governed? The UN discussions have included calls for rules addressing issues such as sustainability, access, benefit sharing and the rights of countries without the ability to conduct space-resource missions themselves.
Finally, there is the idea of safety zones. The accords allow temporary zones around lunar operations to prevent interference. But the Outer Space Treaty says no country can claim sovereignty over the moon or appropriate it through occupation or use. And couldn’t some countries make a temporary zone that eventually functions like a territorial claim?
While some framework for cooperation in space is necessary, it seems hammering out the details will be a debate for years to come.
The Shackleton crater on the moon with an elevation analysis (left) and shaded relief (right). This 12.5-mile-diameter (21-km-diameter) crater near the south pole is in permanent shadow. Image via NASA.
Bottom line: The Artemis Accords are a set guidelines for peaceful space exploration. But questions remain about who makes the rules and controls space resources.
View at EarthSky Community Photos. | Brian Martin in Riverside, California, captured this image on August 19, 2025, and wrote: “I had very nice seeing which afforded me the 2 types of shadows (umbra and penumbra). This is my cleanest Saturn as far as the ring goes where my goal is to keep most of the grey ring in front of the planet and not a bulky black shadow which I believe I achieved well here.” Thank you, Brian! Besides capturing Saturn’s glorious rings, Brian captured the shadow of Titan on Saturn’s surface. Read tips on how to see Saturn’s rings below.
Saturn’s rings are beautiful
Saturn is the most gasp-inducing planet when viewed through a telescope. And it’s currently providing its best views of 2026 as it reaches its October 4 opposition. Saturn looks starlike to the eye alone. It appears as a golden-hued dot and shines steadily, as planets tend to do. Binoculars will enhance its color, and even a small telescope will let you glimpse Saturn’s rings. Veteran observer Alan MacRobert at SkyandTelescope.org has written:
The rings of Saturn should be visible in even the smallest telescope at 25x [magnified by 25 times]. A good 3-inch scope at 50x [magnified by 50 times] can show them as a separate structure detached on all sides from the ball of the planet.
View at EarthSky Community Photos. | Makrem Larnaout of Tunisia captured this image of Saturn on August 6, 2024, and wrote: “I’m excited to share a new image of Saturn, captured with 195 minutes of data using 2 different setups, under average seeing conditions.” Thank you, Makrem!
Attending a star party or astronomy club
Okay, got Saturn? Now … about that telescope. One possibility is to start scouting out a star party near you, where amateur astronomers are set up to show you telescopic objects. For the U.S., check the club map at NASA’s Night Sky Network to find star parties. For clubs outside the U.S., see the list below. You can also call a local university or science museum and ask about star parties. Or maybe a neighbor, or friend, has a telescope stashed in a closet? More possibilities:
Once you can find Saturn in the sky and have a star party to attend, consider the following tips before your ring-viewing session.
View at EarthSky Community Photos. | Steven Bellavia captured this image on September 3, 2026, from Virginia and wrote: “Saturn, with moons Dione, Tethys and Rhea (left-to-right), from 07:30 UTC, September 03, 2026. I may have finally captured the elusive “spokes” which are fuzzy patches on the rings. But it could also be artifacts of capture and processing.” Thank you, Steven!
Tip 1: You need a telescope to see Saturn’s rings
Don’t expect to see the rings in binoculars. You really do need a telescope. A bigger telescope will show you more than a smaller telescope.
Saturn and its rings in 2026. The days around east and west quadrature (when Saturn is located 90 degrees from the sun) are better than opposition for seeing the shadow of or on the rings, and eclipses of the satellites. Image via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.
Tip 2: Consider the tilt of Saturn’s rings
Notice the tilt of the rings. As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In 2017, the north side of the rings opened up most widely (27 degrees), as seen from Earth. That’s the most open this side of the rings has been since 1988.
In 2025, the rings appeared edge-on as seen from Earth in March. After that, we began to see the south side of Saturn’s rings, which will gradually increase to a maximum inclination of 27 degrees by May 2032. By the way, they were almost look edge-on again in late November 2025. And around the October 2026 opposition, the rings are titled -7.5 degrees with the southern side of the ring plane exposed.
The tilt of Saturn’s rings has a great impact on the planet’s overall brightness as seen from Earth. In years when Saturn’s rings are edge-on (2009 and 2025), Saturn does appear considerably dimmer. A computer program by Tom Ruen simulated these Saturn views. Image via Wikimedia Commons (GFDL).
Tip 3: Can you see the rings in 3D?
Ask yourself … do Saturn’s rings look three-dimensional? Again quoting Alan MacRobert at SkyandTelescope.org:
Saturn has a more three-dimensional appearance than any other object in the sky; at least that’s how it looks to me with a 6-inch ‘scope on a night of fine seeing.
Shadows cast by the ring on the planet in front and by the planet on the farther ring can make the image of Saturn pop.
Tip 4: How’s the seeing?
What was Alan talking about in that quote above when he mentioned seeing? Both amateur and professional astronomers talk about the night’s seeing, which affects how clearly and sharply you can see a telescopic image. Seeing isn’t a quality of the telescope; it’s a quality of the air above you. It’s the reason the stars twinkle more on some nights than others.
When the air is particularly turbulent, astronomers say there’s bad seeing. The images in the telescope shimmy and dance. When the air is particularly still, astronomers say there’s good seeing. Seeing can shift from moment to moment as parcels of air move above you. So, as you’re gazing at Saturn, stand as quietly as you can – for as long as you can – and just look. You’ll notice moments when the image suddenly comes into sharper focus.
Other tips to consider
Once you get comfortable viewing Saturn – assuming you’re able to view it again and again, with a telescope of your own – you’ll begin to notice details in the rings.
Today, thanks to spacecraft, we know that Saturn’s rings are incredibly detailed. But, as you stand at your telescope gazing upward, you might be thrilled to witness just one primary division in the rings, the Cassini Division between the A and B rings, named for its French discoverer Jean Cassini.
Seeing this dark division is a good test of the night’s seeing and your telescope’s optical quality, and also of your own eyes’ ability to simply look and notice what you see. By the way, if you’re looking at the rings – which means you’re viewing Saturn through a telescope – also look for one or more of Saturn’s many moons, most notably Titan.
The Opposition Surge
A phenomenon that occurs when Saturn is at opposition is that the rings brighten for a few days. You can only see this a few nights on either side of opposition, which this year occurs on October 4.
This is the Seeliger Effect, which Hugo von Seeliger first described more than 100 years ago. Normally the rings appear as bright as the globe of the planet. But as the planet lines up with the Earth and the sun, more sunlight suddenly gets reflected back to us from the rings than from the globe, and the rings take on an additional level of brightness.
The two mechanisms for this brightening are shadow hiding and a coherent reflection of sunlight off the rings’ particles. Shadow hiding occurs because the shadows are the shortest on the ring particles. The coherent reflection of light occurs because light going straight into the ice particles reflects off of the inner surfaces, then straight back to where it came from.
This brightness surge lasts only a few days; see a study showing this increase. The window for this opportunity is the days around October 4.
Have fun!
Alas, you won’t see Saturn looking like this through a telescope. This is a spacecraft view from Cassini in 2016, showing Saturn’s northern hemisphere. Image via NASA/ JPL-Caltech/ Space Science Institute.
Bottom line: If you want to see Saturn’s rings at their best in 2026, late September and early October is a great time to look. Grab a telescope and read the tips found here!
View at EarthSky Community Photos. | Brian Martin in Riverside, California, captured this image on August 19, 2025, and wrote: “I had very nice seeing which afforded me the 2 types of shadows (umbra and penumbra). This is my cleanest Saturn as far as the ring goes where my goal is to keep most of the grey ring in front of the planet and not a bulky black shadow which I believe I achieved well here.” Thank you, Brian! Besides capturing Saturn’s glorious rings, Brian captured the shadow of Titan on Saturn’s surface. Read tips on how to see Saturn’s rings below.
Saturn’s rings are beautiful
Saturn is the most gasp-inducing planet when viewed through a telescope. And it’s currently providing its best views of 2026 as it reaches its October 4 opposition. Saturn looks starlike to the eye alone. It appears as a golden-hued dot and shines steadily, as planets tend to do. Binoculars will enhance its color, and even a small telescope will let you glimpse Saturn’s rings. Veteran observer Alan MacRobert at SkyandTelescope.org has written:
The rings of Saturn should be visible in even the smallest telescope at 25x [magnified by 25 times]. A good 3-inch scope at 50x [magnified by 50 times] can show them as a separate structure detached on all sides from the ball of the planet.
View at EarthSky Community Photos. | Makrem Larnaout of Tunisia captured this image of Saturn on August 6, 2024, and wrote: “I’m excited to share a new image of Saturn, captured with 195 minutes of data using 2 different setups, under average seeing conditions.” Thank you, Makrem!
Attending a star party or astronomy club
Okay, got Saturn? Now … about that telescope. One possibility is to start scouting out a star party near you, where amateur astronomers are set up to show you telescopic objects. For the U.S., check the club map at NASA’s Night Sky Network to find star parties. For clubs outside the U.S., see the list below. You can also call a local university or science museum and ask about star parties. Or maybe a neighbor, or friend, has a telescope stashed in a closet? More possibilities:
Once you can find Saturn in the sky and have a star party to attend, consider the following tips before your ring-viewing session.
View at EarthSky Community Photos. | Steven Bellavia captured this image on September 3, 2026, from Virginia and wrote: “Saturn, with moons Dione, Tethys and Rhea (left-to-right), from 07:30 UTC, September 03, 2026. I may have finally captured the elusive “spokes” which are fuzzy patches on the rings. But it could also be artifacts of capture and processing.” Thank you, Steven!
Tip 1: You need a telescope to see Saturn’s rings
Don’t expect to see the rings in binoculars. You really do need a telescope. A bigger telescope will show you more than a smaller telescope.
Saturn and its rings in 2026. The days around east and west quadrature (when Saturn is located 90 degrees from the sun) are better than opposition for seeing the shadow of or on the rings, and eclipses of the satellites. Image via Guy Ottewell’s 2026 Astronomical Calendar. Used with permission.
Tip 2: Consider the tilt of Saturn’s rings
Notice the tilt of the rings. As with so much in space (and on Earth), the appearance of Saturn’s rings from Earth is cyclical. In 2017, the north side of the rings opened up most widely (27 degrees), as seen from Earth. That’s the most open this side of the rings has been since 1988.
In 2025, the rings appeared edge-on as seen from Earth in March. After that, we began to see the south side of Saturn’s rings, which will gradually increase to a maximum inclination of 27 degrees by May 2032. By the way, they were almost look edge-on again in late November 2025. And around the October 2026 opposition, the rings are titled -7.5 degrees with the southern side of the ring plane exposed.
The tilt of Saturn’s rings has a great impact on the planet’s overall brightness as seen from Earth. In years when Saturn’s rings are edge-on (2009 and 2025), Saturn does appear considerably dimmer. A computer program by Tom Ruen simulated these Saturn views. Image via Wikimedia Commons (GFDL).
Tip 3: Can you see the rings in 3D?
Ask yourself … do Saturn’s rings look three-dimensional? Again quoting Alan MacRobert at SkyandTelescope.org:
Saturn has a more three-dimensional appearance than any other object in the sky; at least that’s how it looks to me with a 6-inch ‘scope on a night of fine seeing.
Shadows cast by the ring on the planet in front and by the planet on the farther ring can make the image of Saturn pop.
Tip 4: How’s the seeing?
What was Alan talking about in that quote above when he mentioned seeing? Both amateur and professional astronomers talk about the night’s seeing, which affects how clearly and sharply you can see a telescopic image. Seeing isn’t a quality of the telescope; it’s a quality of the air above you. It’s the reason the stars twinkle more on some nights than others.
When the air is particularly turbulent, astronomers say there’s bad seeing. The images in the telescope shimmy and dance. When the air is particularly still, astronomers say there’s good seeing. Seeing can shift from moment to moment as parcels of air move above you. So, as you’re gazing at Saturn, stand as quietly as you can – for as long as you can – and just look. You’ll notice moments when the image suddenly comes into sharper focus.
Other tips to consider
Once you get comfortable viewing Saturn – assuming you’re able to view it again and again, with a telescope of your own – you’ll begin to notice details in the rings.
Today, thanks to spacecraft, we know that Saturn’s rings are incredibly detailed. But, as you stand at your telescope gazing upward, you might be thrilled to witness just one primary division in the rings, the Cassini Division between the A and B rings, named for its French discoverer Jean Cassini.
Seeing this dark division is a good test of the night’s seeing and your telescope’s optical quality, and also of your own eyes’ ability to simply look and notice what you see. By the way, if you’re looking at the rings – which means you’re viewing Saturn through a telescope – also look for one or more of Saturn’s many moons, most notably Titan.
The Opposition Surge
A phenomenon that occurs when Saturn is at opposition is that the rings brighten for a few days. You can only see this a few nights on either side of opposition, which this year occurs on October 4.
This is the Seeliger Effect, which Hugo von Seeliger first described more than 100 years ago. Normally the rings appear as bright as the globe of the planet. But as the planet lines up with the Earth and the sun, more sunlight suddenly gets reflected back to us from the rings than from the globe, and the rings take on an additional level of brightness.
The two mechanisms for this brightening are shadow hiding and a coherent reflection of sunlight off the rings’ particles. Shadow hiding occurs because the shadows are the shortest on the ring particles. The coherent reflection of light occurs because light going straight into the ice particles reflects off of the inner surfaces, then straight back to where it came from.
This brightness surge lasts only a few days; see a study showing this increase. The window for this opportunity is the days around October 4.
Have fun!
Alas, you won’t see Saturn looking like this through a telescope. This is a spacecraft view from Cassini in 2016, showing Saturn’s northern hemisphere. Image via NASA/ JPL-Caltech/ Space Science Institute.
Bottom line: If you want to see Saturn’s rings at their best in 2026, late September and early October is a great time to look. Grab a telescope and read the tips found here!
The famous Grand Prismatic Spring in Yellowstone National Park is a sign of the geothermal activity in this region. The Yellowstone supervolcano has had 3 massive eruptions in history. What if one of those happened today? Would it end humanity? Image via Lucy Whitt. Used with permission.
What if a worst-case scenario Yellowstone supervolcano eruption happened? It would be a civilization-scale disaster. But it would not necessarily wipe out humanity.
The eruption would devastate much of North America. Massive ashfall, pyroclastic flows and infrastructure failures would disrupt civilization in this region. Plus, volcanic aerosols would cool the global climate.
The effects could last for decades. Food shortages, disease, economic disruption and climate changes could cause enormous loss of life. Yet ecosystems and agriculture would gradually recover and humanity would persist.
Would a Yellowstone supervolcano eruption end humanity today?
Around 631,000 years ago — a geological blink of an eye — catastrophe unfolded in what is now northwestern Wyoming in the U.S. During what is thought to have been a series of immense volcanic eruptions, life within hundreds of kilometers of the blasts was shattered. Ash was dispersed across much of North America and the effects were felt worldwide. This was a super-eruption of the massive volcanic system located in what is now Yellowstone National Park.
No known human witnessed the cataclysm. As far as we know, early humans had not yet reached the continent. Across oceans, perhaps early humans did wonder at the hazier skies and unusually vivid sunsets. Volcanic particles circulating in the sky cooled their climate and likely affected their weather patterns and lives. Whether they noted these changes — or connected them to any distant event — is unknowable.
Today, humanity would certainly notice. We already know that a super-eruption on this scale would be a threat to civilization as we know it. So what exactly would we experience if Yellowstone erupted? We are experts in disasters and volcanoes. What follows is a thought experiment into what might happen in the worst-case scenario. We’ve based our hypothesis on research and by examining how countries have dealt with disasters in recent years.
T-2 months
Shortly after 6 a.m., an analyst at the University of Utah Seismograph Stations sees a series of sharp spikes interrupting the usually quiet wavy lines recorded by Yellowstone’s earthquake monitors. The measurements represent earthquakes detected beneath Yellowstone overnight. The scientist raises an eyebrow and takes a deep breath. These observations don’t fit with Yellowstone’s usual behavior.
People often imagine Yellowstone as a sleeping “supervolcano”. It may sleep, but its geological processes never do. An array of instruments monitors its activity, and any changes in it. A dense network of seismometers records earthquakes in the region. Around the clock, data feeds in from GPS stations, strainmeters (instruments which measure deformations and changes in the shape of the Earth’s crust) and sensors positioned within its active geyser areas. Satellite observations, gas sampling and field surveys add plenty more information.
Scientists look at the number of earthquakes along with their location, depth and size. Earthquake “swarms” warrant particular attention, especially when they appear to be migrating through the crust (Earth’s solid, outermost rocky shell) or becoming progressively shallower. Such patterns can indicate that magma or pressurized hydrothermal fluids (hot, mineral-rich water) is moving upwards.
Our scientist is relieved to discover that most of the unusual tremors are tiny, too weak to have been felt. But together, they form an unusually concentrated swarm. The analyst checks the signals against neighboring seismometers and, more out of curiosity than concern, contacts colleagues at several partner organizations comprising the Yellowstone Volcano Observatory (YVO) in order to follow YVO’s response plan.
They deduce that, overnight, instruments have recorded a tightening cluster of earthquakes beneath Yellowstone’s vast caldera, which is roughly 55–70 kilometers (34–43 miles) across. Yellowstone experiences thousands of earthquakes each year, and swarms are not unusual. But this one appears to be migrating ever so slightly upwards. Still, an earthquake swarm by itself doesn’t mean Yellowstone is preparing to erupt, nor does ground deformation, changing temperatures or gas emissions. Scientists are more concerned about several such changes happening together.
The team of scientists decides to wait and see what happens next.
T-1 month
Four weeks later, the swarm has continued to migrate upwards. New events are also appearing along a narrow zone beneath the caldera, notes the analyst, who has now lost their appetite for both food and caution and is writing reports designed to be alarming. GPS stations above the swarm have begun moving apart. Measurements of strain have increased and satellite radar reveals the cause: there’s a broad area of accelerating uplift of the ground.
The surface of a volcano inflates and deflates as the magma chamber below it changes in pressure. Measuring this motion can help tell scientists whether a volcano is building to an eruption. Image via USGS and Jessica Murray-Moraleda, CC BY-SA.
Together, the observations are consistent with magma forcing its way into the crust, as seen in places like Hawai’i prior to eruptions. Reassuringly for YVO staff, Yellowstone has produced similarly alarming combinations of signals before with no subsequent eruptions. Between 2013 and 2014, parts of the caldera began rising at rates of more than 15 centimeters (6 inches) a year and earthquake activity increased.
This culminated in a magnitude 4.8 earthquake, the largest recorded at Yellowstone since 1975. Shortly after, the uplift changed to subsidence (the ground moving downward) and scientists concluded that the episode was associated with hydrothermal fluid movements rather than magma.
The Biscuit basin explosion at Yellowstone was an example of an eruption caused by hydrothermal fluid rather than magma.
Mindful of the need to keep the public informed without causing unnecessary alarm, YVO responds cautiously. A duty scientist assumes responsibility for assessing the incoming data. Additional, temporary seismometers and GPS units are deployed to provide more precise data, and gas and water are sampled more frequently.
YVO begins closer coordination with the National Park Service and emergency management authorities. They review road closures, public communications and evacuation plans. Perhaps ominously, but to err on the side of caution, Yellowstone’s Volcano Alert Level is raised from “normal” to “advisory”, indicating that unrest is above its established background level.
These developments are worrisome enough that scientists start speculating about a major eruption’s impacts. The media take an interest, but the volcanologists have learned how damaging it can be when volcanic uncertainties morph into a full-blown dispute, played out in public.
Scientists privately discuss differences in interpretations, agreeing on regular updates for the public via media briefings and social media postings. As the volcano’s activity continues to ramp up, high-level decision-makers are alerted that this situation could become a major catastrophe. The probability of it happening within three months increases from 6-9% to 21-27%.
Due to the uncertainties, the politicians make no specific declaration. The US’s Federal Emergency Management Agency nevertheless starts drawing up plans for a large-scale evacuation. They express confidence in public while perhaps fearing in private that a worst-case scenario could make it hopeless to try to save everyone.
Over the following fortnight, the unrest escalates dramatically. Earthquakes become more frequent and shallower. Long-period seismicity (much gentler earthquakes, usually caused by fluid movement rather than faults shifting and known to occur at Yellowstone) and sustained volcanic tremors suggest magma and pressurized fluids are forcing open fractures in the ground.
The uplift accelerates and GPS stations move centimeters in days. Geyser activity becomes increasingly erratic. Even the Old Faithful geyser becomes less faithful: its usually regular eruptions become harder to predict. Meanwhile, gas measurements and changes in spring water chemistry indicate an increased input of carbon dioxide and sulfurous gases into Yellowstone’s hydrothermal system. Taken together with the shallow earthquakes and rapid uplift, the concern is that magma may be moving upwards.
T-2 weeks: ‘It’s gonna blow!’
These new observations lead to a press conference describing an 85-92% probability of a cataclysmic eruption within three weeks. At this point, the YVO raises Yellowstone warning to “watch”, and the USGS raises the Aviation Color Code to orange, with aircraft rerouted around the region.
An evacuation zone extending 100 kilometers (62 miles) beyond Yellowstone National Park is announced, affecting roughly 200,000 residents, as well as thousands of visitors in the region. The topic now dominates both traditional and social media. The attention likely spawns detractors as well as conspiracists. The former claim that nothing will happen. The latter spread the disinformation that YVO is being paid by foreign shadow billionaires to bring down the U.S. so that other countries can control the world’s economy.
Now that a super-eruption appears imminent with high confidence, world leaders swing into action. They must make a choice: help each other as a global village or repeat COVID-19 style global shuttering.
If they choose collaboration, then they start evacuations, moving people as far as needed, including across international borders. This would involve supporting them with adequate homes, water, food, electricity and community through schools, jobs, transport and safety. Achieving all this seems unlikely, since most of the world’s population has always lacked it. Nonetheless, the U.S. has the money, skills and goods to evacuate and resettle the huge numbers, if leaders cooperate and use everything available.
More likely, many countries could be reticent to accept “volcano refugees,” making excuses — perhaps legitimate ones — that they don’t have the money, resources or space to safely settle so many people so swiftly. They are further stretched by those who self-evacuate through having more than one passport, along with the wealth or the social network to start afresh.
Charities step in to help some people leave on chartered planes, as well as via long, excruciating journeys on overcrowded trains and buses. The most marginalized and poorest may have no option but to stay behind. Some might join the minorities who do not believe the eruption will happen, who think their well-stocked underground bunkers will protect them (an overly optimistic belief), or who would rather die at home than live in a foreign land with a devastated world.
T=0
In an instant, seismic instruments are overwhelmed by an intense burst of shallow earthquakes. Expanding clouds of steam rise from newly opened cracks. The YVO and USGS have no choice but to raise the warning level and Aviation Color Codes to red: a dangerous eruption is imminent.
The eruption does not begin with the entire caldera exploding at once. Instead, rising magma intrudes into Yellowstone’s shallow hydrothermal system, rapidly vaporizing immense volumes of water. At atmospheric pressure, water can expand in volume around 1,700 times when converted to steam. Trapped beneath the surface, this rapid expansion triggers violent so-called phreatomagmatic explosions that send superheated steam, mud and shattered blocks of rock kilometers into the air.
There are no human casualties yet, thanks to the wide exclusion zones on land and in the air. Wildlife, livestock and vegetation are not as fortunate. Within roughly 4–6 kilometers (2.4-3.7 miles) of the initial eruption sites, the landscape is battered by falling rock, ash and mud. Beyond the exclusion zone, people watch an impressive two-kilometer-high (1.2 miles) plume rise into the sky, but it rapidly grows larger, and any sense of relief is short-lived.
A few hours later, gas-rich magma, 650-800°C (1,200-1,470°F) in temperature — well above the melting points of lead and zinc — breaks through the fractured surface. As the confining pressure falls, dissolved gases separate into distinct components from the melt and expand violently. The magma fragments into pumice (porous rock) and ash while tearing away huge fragments of the surrounding rock from the walls of the erupting vent.
Expanding gases and intense heat drive this material upwards, creating a vast eruption column rising 30–50 kilometers (18–31 miles) into the atmosphere. That’s far above commercial passenger aircraft, which usually cruise at up to about 13 kilometers (8 miles). On this clear morning, its upper reaches are visible from Denver, some 800 kilometers (500 miles) away.
As the eruption continues and the volume of material expelled mounts, scientists realize it might be the opening stages of a VEI 8 super-eruption (magnitude 8 or greater). That’s the highest formal notch on a scale used to measure the size of explosive volcanic eruptions. It was 74,000 years ago that humanity last witnessed this scale of eruption with Toba in Indonesia.
The immense umbrella cloud that forms does not behave like a normal ash plume that simply drifts with the prevailing wind. Its momentum initially drives ash outwards in every direction. It spreads hundreds of kilometers before high-altitude winds take over and carry fine ash thousands of kilometers downwind within a day.
After a few hours of continuous eruption, parts of the column collapse, generating scorching pyroclastic density currents (extremely hot, fast-moving mixtures of gas, ash and rock fragments). These surge for tens of kilometers, splintering trees, igniting forests and burying the remnants beneath hot ash and pumice.
Anyone within this zone is pulverized by the blasts, crisped by the heat or asphyxiated by the ash. There may be up to 1,000 immediate human deaths, including people who refused to move. It is too dangerous to recover most bodies. And even if it were possible, many bodies no longer exist to be recovered.
Outside the main pyroclastic density current zone, casualties mount from vehicle crashes as drivers lose visibility or skid due to ash, from heart and breathing difficulties and from suicide. Vegetation fires spreading beyond the immediate burn zone add perhaps hundreds of fatalities from burning, smoke inhalation and vehicle crashes.
As the magma continues to escape, sections of the unsupported ground subside, opening new fractures and vents while feeding further eruptive columns and pyroclastic density currents. Hundreds of kilometers away — in Denver and along the Canadian border — heavy ashfall darkens the sky, obstructs roads and disrupts power, water supplies and communications. This ash devastates farmland across at least eight states.
Further immediate deaths could result from loss of power disrupting traffic and street lights; curtailing health services including surgery and obtaining prescriptions; and electrocution, fire and carbon monoxide poisoning from trying to set up and operate home electricity generators. Looting and increasing crime during disasters is typically rare, but it could happen in a more desperate worst-case scenario, adding to the casualty toll.
Over the coming days, the eruption continues in pulses as sections of the caldera collapse and new vents open. Successive column collapses generate pyroclastic density currents with the resulting deposits reaching several hundred meters in thickness, as they did in the last super-eruption.
Nearby infrastructure is shattered and entombed beneath the deposits. Airports close because ash interferes with aircraft and other transport networks falter. Communities across all states bordering Wyoming face darkness, breathing difficulties and roofs collapsing under accumulated ash. As the eruption eventually begins to weaken, sulfur dioxide high in the atmosphere forms sunlight-reflecting sulphate aerosols that spread around the northern hemisphere to influence the world’s climate for several years.
T+3 days
Three days into the eruption, much of North America is living in the shadow of Yellowstone. Each successive powerful eruptive pulse sends another column tens of kilometers upwards, from where it spreads into a new umbrella cloud.
Within Wyoming and neighboring states, conditions are catastrophic. Billings, Montana, the nearest large city, is disappearing beneath what will eventually exceed a meter of ash (one published model of a Yellowstone super-eruption predicts the city as receiving up to 1.8 meters [6 feet] of ash). Salt Lake City, Utah, and Boise, Idaho, receive tens of centimeters. For southern Canada, much of the US and northern Mexico, day becomes twilight and breathing outdoors without masks becomes increasingly difficult. People on other continents watch in trepidation under vivid, red-orange sunrises and sunsets.
Back in the U.S., electricity networks begin failing. Warnings had not been heeded that damp ash conducts electricity, short circuiting power lines and substations. Ash clogs machinery and generator intakes. Its weight damages cables and weaker structures.
Infrastructure damage at Hebgen Lake due to the 7.2 magnitude earthquake of 1959. Image via I.J. Witkind. USGS Photographic Library/ Wikipedia.
As electricity fails, so do water pumps, sewage treatment, heating systems, fuel stations and mobile phone and internet networks. People are scared and supermarket shelves empty nationwide as regional and national supply chains begin to break down.
T+2 weeks
Over the following weeks, the crisis becomes one of survival. Repeated ashfall blocks roads, overwhelms drainage systems and damages roofs. During rain, dry ash turns into a dense slurry that makes clearance work harder. Airports remain closed or severely disrupted across much of North America, while railways, freight depots and farms struggle to operate. Livestock and crops die where pasture and water supplies are buried or contaminated by ash.
Large areas close to Yellowstone remain evacuated, while across the U.S., shelter, fuel, food and clean water become increasingly scarce. Some countries airlift or airdrop humanitarian relief supplies. But they are also concerned about stockpiling for themselves. Losses to agriculture, transport and insurance — with many other businesses and services closed — could lead Canada, Mexico and most Caribbean and Central American countries to declare states of emergency. This is partly due to direct impacts on those countries and partly due to disruption across the U.S. and people fleeing from it.
T+4 months
Several months later, eruptions have weakened to intermittent explosions, but the threat of renewed activity remains. For millions, the disaster is far from over. Dry, windy days lift ash back into the air, while rain and snow turn it into a heavy deposit blocking drains and damaging infrastructure. Eye and throat irritation are widespread. People with asthma and other respiratory conditions face serious health risks under reduced and overworked health services.
Water treatment and power plants struggle with ash contamination, equipment failures, lack of spare parts and overwhelming demand, disrupting essential medical and industrial processes. Crops across the most heavily affected regions have been buried. The loss of American and Canadian grain, maize and soya exports drives global food prices upwards.
Flights gradually resume in less affected areas, but airports across North America repeatedly close whenever winds remobilize the ash. The unreliable airspace and transport networks — coupled with agricultural losses, business disruption and reconstruction costs — trigger banking and insurance crises, producing a global recession.
Meanwhile, the atmospheric effects become global. Most volcanic ash has fallen out, but sulfur dioxide injected into the stratosphere produces sulphate aerosols which reflect a significant proportion of the sun’s energy. Scientists call it a “volcanic cooling episode,” avoiding the term “a new ice age”. Modelling suggests it’s unlikely to cool the global average by more than about 1.5°C, although particular regions and seasons could experience much larger changes. Notably, central North America remains far cooler than before the eruption.
T+10 years
In the years following the eruption, the world moves into long-term recovery and rebuilding. People across the world adapt to a more agrarian lifestyle, learning to fill the land with root vegetables, grains and legumes. With far less leisure time and diminished income, recreational facilities are turned over to food production, notably small-scale greenhouses and vertical farming for producing varied fruits, vegetables, nuts and legumes.
Livestock decreases due to lack of land and feed, opening up more space for crops. People still eating meat typically either hunt big game or trap smaller birds and mammals. Insect farming tends to dominate the re-establishment of bird or mammal farms. People living near coasts, rivers and lakes ramp up fishing, depleting stocks rapidly until controls are enacted in some locations, along with increased farming for seaweed. Where rules are not agreed or enforced, starvation and migration are rampant.
Freshwater availability varies. The world’s climate has changed, providing ample rainfall in some places while drying out others. Large-scale water treatment technology remains known and used. But supply lines for chemicals and spare parts are unreliable. Many people develop local approaches and manage while others suffer contaminated water and disease, including cholera, dengue fever and malaria, just as billions did before the eruption.
Before the eruption, around 4.4 billion people from the world’s population of 8.3 billion lacked full, safe freshwater access. A decade after the eruption, it’s possible that 4.8 billion people lack such freshwater, while the world’s population may have declined to 7.9 billion due to spikes in elderly and infant mortality.
For the eruption’s survivors, disease and death are still rising. The eruption may well provide substantive, long-term evidence for the carcinogenic level of silica in the ash. A small but statistically significant increase in diagnoses of both silicosis (an irreversible lung disease) and lung cancer appears from exposure to ash, with similar results for cardiovascular disease in people breathing in ash particles.
Rates are likely higher than measured, because health systems across a continent were knocked out by the eruption and struggling to recover ten years later. The worst part is that the lack of health systems means that many who are diagnosed cannot be treated properly. Survivable diagnoses become lethal.
Inside the eruption zone, two decades follow of a grey landscape. It appears almost lifeless, with the ash transformed into raging mudflows called lahars in every storm. But vegetation, starting with grasslands and shifting to forests, creeps back into the swathes wiped out in the explosion and people follow. These new pioneers coax the landscape into fertile framing, helping to feed hungry populations.
A lahar travels down a river valley in Guatemala near the Santa María volcano, 1989. Image via Wikipedia/ USGS geologist Jeff Marso.
The dispersed ash eventually settles out of the atmosphere. That permits the sun’s rays to shine fully on the surface again, reviving agriculture and ecosystems. It also revives fears of human-caused climate change, despite the volcano-induced reduction in greenhouse gas emissions. Scientists work hard to determine whether the global climate has been knocked onto a new trajectory — which might be better or worse for human beings — or whether the heat stored in the atmosphere and oceans from humanity’s greenhouse gas burning will once again force a rapidly heating globe.
Additionally, scientists want to calculate deaths, injuries and loss to quality of life. Excess mortality analyses could suggest 0.7-1.3 billion premature deaths due to the eruption and its impacts. Perhaps double that number experienced temporary or permanent health effects but survived, although some will say that 100% of humanity was directly affected.
The good news, at least for our species, is that this unstoppable power of volcanism changed the planet, but did not end humanity … or come close to doing so.
T+1 million years
A creature descends to Earth from a sleek spacecraft, still humanoid but far removed from its ancestor species Homo sapiens sapiens. Tjjze (the pronoun used) has absorbed all the scant information available about ancient “Earth” and is curious to learn more.
The most notable material is the rise of its first technological civilization just over a million years ago. This was followed by the species abandoning the planet as it changed 140,000-160,000 years ago — becoming taller, sleeker, with longer limbs, and with larger hands, heads and brains — having already established itself around the galaxy. In the remaining lore, myths recur of episodes of runaway planetary temperature changes, hot and cold, as well as a series of volcanic blasts that changed the globe.
Tjjze observes that the vegetation is lush and the H2O is plentiful. It provides ample food and water for the bizarre animals and ecosystems. A rapid scan reveals much below the surface. In fact, a large roughly ellipse-shaped ridge made of rock appears prominently underneath the top layers. Yes, this particular region, about 24.3 cqurzots in radius, is definitely lower than the vast plains outside the depression. This seems to indicate an ancient volcanic eruption. And to leave a scar this big, it must have been gigantic.
Tjjze warps the equivalent of the face into the equivalent of a frown as more data are revealed. Indeed, this definitely looks like a caldera. And the age is coming in at around a million years (plus/minus).
Could it have erupted during the time of the technological civilization? Or were they lucky to have just missed it? It is impossible to really know.
Bottom line: Yellowstone has undergone three massive super-eruptions in the past. If the Yellowstone supervolcano erupted today, would humanity survive?
The famous Grand Prismatic Spring in Yellowstone National Park is a sign of the geothermal activity in this region. The Yellowstone supervolcano has had 3 massive eruptions in history. What if one of those happened today? Would it end humanity? Image via Lucy Whitt. Used with permission.
What if a worst-case scenario Yellowstone supervolcano eruption happened? It would be a civilization-scale disaster. But it would not necessarily wipe out humanity.
The eruption would devastate much of North America. Massive ashfall, pyroclastic flows and infrastructure failures would disrupt civilization in this region. Plus, volcanic aerosols would cool the global climate.
The effects could last for decades. Food shortages, disease, economic disruption and climate changes could cause enormous loss of life. Yet ecosystems and agriculture would gradually recover and humanity would persist.
Would a Yellowstone supervolcano eruption end humanity today?
Around 631,000 years ago — a geological blink of an eye — catastrophe unfolded in what is now northwestern Wyoming in the U.S. During what is thought to have been a series of immense volcanic eruptions, life within hundreds of kilometers of the blasts was shattered. Ash was dispersed across much of North America and the effects were felt worldwide. This was a super-eruption of the massive volcanic system located in what is now Yellowstone National Park.
No known human witnessed the cataclysm. As far as we know, early humans had not yet reached the continent. Across oceans, perhaps early humans did wonder at the hazier skies and unusually vivid sunsets. Volcanic particles circulating in the sky cooled their climate and likely affected their weather patterns and lives. Whether they noted these changes — or connected them to any distant event — is unknowable.
Today, humanity would certainly notice. We already know that a super-eruption on this scale would be a threat to civilization as we know it. So what exactly would we experience if Yellowstone erupted? We are experts in disasters and volcanoes. What follows is a thought experiment into what might happen in the worst-case scenario. We’ve based our hypothesis on research and by examining how countries have dealt with disasters in recent years.
T-2 months
Shortly after 6 a.m., an analyst at the University of Utah Seismograph Stations sees a series of sharp spikes interrupting the usually quiet wavy lines recorded by Yellowstone’s earthquake monitors. The measurements represent earthquakes detected beneath Yellowstone overnight. The scientist raises an eyebrow and takes a deep breath. These observations don’t fit with Yellowstone’s usual behavior.
People often imagine Yellowstone as a sleeping “supervolcano”. It may sleep, but its geological processes never do. An array of instruments monitors its activity, and any changes in it. A dense network of seismometers records earthquakes in the region. Around the clock, data feeds in from GPS stations, strainmeters (instruments which measure deformations and changes in the shape of the Earth’s crust) and sensors positioned within its active geyser areas. Satellite observations, gas sampling and field surveys add plenty more information.
Scientists look at the number of earthquakes along with their location, depth and size. Earthquake “swarms” warrant particular attention, especially when they appear to be migrating through the crust (Earth’s solid, outermost rocky shell) or becoming progressively shallower. Such patterns can indicate that magma or pressurized hydrothermal fluids (hot, mineral-rich water) is moving upwards.
Our scientist is relieved to discover that most of the unusual tremors are tiny, too weak to have been felt. But together, they form an unusually concentrated swarm. The analyst checks the signals against neighboring seismometers and, more out of curiosity than concern, contacts colleagues at several partner organizations comprising the Yellowstone Volcano Observatory (YVO) in order to follow YVO’s response plan.
They deduce that, overnight, instruments have recorded a tightening cluster of earthquakes beneath Yellowstone’s vast caldera, which is roughly 55–70 kilometers (34–43 miles) across. Yellowstone experiences thousands of earthquakes each year, and swarms are not unusual. But this one appears to be migrating ever so slightly upwards. Still, an earthquake swarm by itself doesn’t mean Yellowstone is preparing to erupt, nor does ground deformation, changing temperatures or gas emissions. Scientists are more concerned about several such changes happening together.
The team of scientists decides to wait and see what happens next.
T-1 month
Four weeks later, the swarm has continued to migrate upwards. New events are also appearing along a narrow zone beneath the caldera, notes the analyst, who has now lost their appetite for both food and caution and is writing reports designed to be alarming. GPS stations above the swarm have begun moving apart. Measurements of strain have increased and satellite radar reveals the cause: there’s a broad area of accelerating uplift of the ground.
The surface of a volcano inflates and deflates as the magma chamber below it changes in pressure. Measuring this motion can help tell scientists whether a volcano is building to an eruption. Image via USGS and Jessica Murray-Moraleda, CC BY-SA.
Together, the observations are consistent with magma forcing its way into the crust, as seen in places like Hawai’i prior to eruptions. Reassuringly for YVO staff, Yellowstone has produced similarly alarming combinations of signals before with no subsequent eruptions. Between 2013 and 2014, parts of the caldera began rising at rates of more than 15 centimeters (6 inches) a year and earthquake activity increased.
This culminated in a magnitude 4.8 earthquake, the largest recorded at Yellowstone since 1975. Shortly after, the uplift changed to subsidence (the ground moving downward) and scientists concluded that the episode was associated with hydrothermal fluid movements rather than magma.
The Biscuit basin explosion at Yellowstone was an example of an eruption caused by hydrothermal fluid rather than magma.
Mindful of the need to keep the public informed without causing unnecessary alarm, YVO responds cautiously. A duty scientist assumes responsibility for assessing the incoming data. Additional, temporary seismometers and GPS units are deployed to provide more precise data, and gas and water are sampled more frequently.
YVO begins closer coordination with the National Park Service and emergency management authorities. They review road closures, public communications and evacuation plans. Perhaps ominously, but to err on the side of caution, Yellowstone’s Volcano Alert Level is raised from “normal” to “advisory”, indicating that unrest is above its established background level.
These developments are worrisome enough that scientists start speculating about a major eruption’s impacts. The media take an interest, but the volcanologists have learned how damaging it can be when volcanic uncertainties morph into a full-blown dispute, played out in public.
Scientists privately discuss differences in interpretations, agreeing on regular updates for the public via media briefings and social media postings. As the volcano’s activity continues to ramp up, high-level decision-makers are alerted that this situation could become a major catastrophe. The probability of it happening within three months increases from 6-9% to 21-27%.
Due to the uncertainties, the politicians make no specific declaration. The US’s Federal Emergency Management Agency nevertheless starts drawing up plans for a large-scale evacuation. They express confidence in public while perhaps fearing in private that a worst-case scenario could make it hopeless to try to save everyone.
Over the following fortnight, the unrest escalates dramatically. Earthquakes become more frequent and shallower. Long-period seismicity (much gentler earthquakes, usually caused by fluid movement rather than faults shifting and known to occur at Yellowstone) and sustained volcanic tremors suggest magma and pressurized fluids are forcing open fractures in the ground.
The uplift accelerates and GPS stations move centimeters in days. Geyser activity becomes increasingly erratic. Even the Old Faithful geyser becomes less faithful: its usually regular eruptions become harder to predict. Meanwhile, gas measurements and changes in spring water chemistry indicate an increased input of carbon dioxide and sulfurous gases into Yellowstone’s hydrothermal system. Taken together with the shallow earthquakes and rapid uplift, the concern is that magma may be moving upwards.
T-2 weeks: ‘It’s gonna blow!’
These new observations lead to a press conference describing an 85-92% probability of a cataclysmic eruption within three weeks. At this point, the YVO raises Yellowstone warning to “watch”, and the USGS raises the Aviation Color Code to orange, with aircraft rerouted around the region.
An evacuation zone extending 100 kilometers (62 miles) beyond Yellowstone National Park is announced, affecting roughly 200,000 residents, as well as thousands of visitors in the region. The topic now dominates both traditional and social media. The attention likely spawns detractors as well as conspiracists. The former claim that nothing will happen. The latter spread the disinformation that YVO is being paid by foreign shadow billionaires to bring down the U.S. so that other countries can control the world’s economy.
Now that a super-eruption appears imminent with high confidence, world leaders swing into action. They must make a choice: help each other as a global village or repeat COVID-19 style global shuttering.
If they choose collaboration, then they start evacuations, moving people as far as needed, including across international borders. This would involve supporting them with adequate homes, water, food, electricity and community through schools, jobs, transport and safety. Achieving all this seems unlikely, since most of the world’s population has always lacked it. Nonetheless, the U.S. has the money, skills and goods to evacuate and resettle the huge numbers, if leaders cooperate and use everything available.
More likely, many countries could be reticent to accept “volcano refugees,” making excuses — perhaps legitimate ones — that they don’t have the money, resources or space to safely settle so many people so swiftly. They are further stretched by those who self-evacuate through having more than one passport, along with the wealth or the social network to start afresh.
Charities step in to help some people leave on chartered planes, as well as via long, excruciating journeys on overcrowded trains and buses. The most marginalized and poorest may have no option but to stay behind. Some might join the minorities who do not believe the eruption will happen, who think their well-stocked underground bunkers will protect them (an overly optimistic belief), or who would rather die at home than live in a foreign land with a devastated world.
T=0
In an instant, seismic instruments are overwhelmed by an intense burst of shallow earthquakes. Expanding clouds of steam rise from newly opened cracks. The YVO and USGS have no choice but to raise the warning level and Aviation Color Codes to red: a dangerous eruption is imminent.
The eruption does not begin with the entire caldera exploding at once. Instead, rising magma intrudes into Yellowstone’s shallow hydrothermal system, rapidly vaporizing immense volumes of water. At atmospheric pressure, water can expand in volume around 1,700 times when converted to steam. Trapped beneath the surface, this rapid expansion triggers violent so-called phreatomagmatic explosions that send superheated steam, mud and shattered blocks of rock kilometers into the air.
There are no human casualties yet, thanks to the wide exclusion zones on land and in the air. Wildlife, livestock and vegetation are not as fortunate. Within roughly 4–6 kilometers (2.4-3.7 miles) of the initial eruption sites, the landscape is battered by falling rock, ash and mud. Beyond the exclusion zone, people watch an impressive two-kilometer-high (1.2 miles) plume rise into the sky, but it rapidly grows larger, and any sense of relief is short-lived.
A few hours later, gas-rich magma, 650-800°C (1,200-1,470°F) in temperature — well above the melting points of lead and zinc — breaks through the fractured surface. As the confining pressure falls, dissolved gases separate into distinct components from the melt and expand violently. The magma fragments into pumice (porous rock) and ash while tearing away huge fragments of the surrounding rock from the walls of the erupting vent.
Expanding gases and intense heat drive this material upwards, creating a vast eruption column rising 30–50 kilometers (18–31 miles) into the atmosphere. That’s far above commercial passenger aircraft, which usually cruise at up to about 13 kilometers (8 miles). On this clear morning, its upper reaches are visible from Denver, some 800 kilometers (500 miles) away.
As the eruption continues and the volume of material expelled mounts, scientists realize it might be the opening stages of a VEI 8 super-eruption (magnitude 8 or greater). That’s the highest formal notch on a scale used to measure the size of explosive volcanic eruptions. It was 74,000 years ago that humanity last witnessed this scale of eruption with Toba in Indonesia.
The immense umbrella cloud that forms does not behave like a normal ash plume that simply drifts with the prevailing wind. Its momentum initially drives ash outwards in every direction. It spreads hundreds of kilometers before high-altitude winds take over and carry fine ash thousands of kilometers downwind within a day.
After a few hours of continuous eruption, parts of the column collapse, generating scorching pyroclastic density currents (extremely hot, fast-moving mixtures of gas, ash and rock fragments). These surge for tens of kilometers, splintering trees, igniting forests and burying the remnants beneath hot ash and pumice.
Anyone within this zone is pulverized by the blasts, crisped by the heat or asphyxiated by the ash. There may be up to 1,000 immediate human deaths, including people who refused to move. It is too dangerous to recover most bodies. And even if it were possible, many bodies no longer exist to be recovered.
Outside the main pyroclastic density current zone, casualties mount from vehicle crashes as drivers lose visibility or skid due to ash, from heart and breathing difficulties and from suicide. Vegetation fires spreading beyond the immediate burn zone add perhaps hundreds of fatalities from burning, smoke inhalation and vehicle crashes.
As the magma continues to escape, sections of the unsupported ground subside, opening new fractures and vents while feeding further eruptive columns and pyroclastic density currents. Hundreds of kilometers away — in Denver and along the Canadian border — heavy ashfall darkens the sky, obstructs roads and disrupts power, water supplies and communications. This ash devastates farmland across at least eight states.
Further immediate deaths could result from loss of power disrupting traffic and street lights; curtailing health services including surgery and obtaining prescriptions; and electrocution, fire and carbon monoxide poisoning from trying to set up and operate home electricity generators. Looting and increasing crime during disasters is typically rare, but it could happen in a more desperate worst-case scenario, adding to the casualty toll.
Over the coming days, the eruption continues in pulses as sections of the caldera collapse and new vents open. Successive column collapses generate pyroclastic density currents with the resulting deposits reaching several hundred meters in thickness, as they did in the last super-eruption.
Nearby infrastructure is shattered and entombed beneath the deposits. Airports close because ash interferes with aircraft and other transport networks falter. Communities across all states bordering Wyoming face darkness, breathing difficulties and roofs collapsing under accumulated ash. As the eruption eventually begins to weaken, sulfur dioxide high in the atmosphere forms sunlight-reflecting sulphate aerosols that spread around the northern hemisphere to influence the world’s climate for several years.
T+3 days
Three days into the eruption, much of North America is living in the shadow of Yellowstone. Each successive powerful eruptive pulse sends another column tens of kilometers upwards, from where it spreads into a new umbrella cloud.
Within Wyoming and neighboring states, conditions are catastrophic. Billings, Montana, the nearest large city, is disappearing beneath what will eventually exceed a meter of ash (one published model of a Yellowstone super-eruption predicts the city as receiving up to 1.8 meters [6 feet] of ash). Salt Lake City, Utah, and Boise, Idaho, receive tens of centimeters. For southern Canada, much of the US and northern Mexico, day becomes twilight and breathing outdoors without masks becomes increasingly difficult. People on other continents watch in trepidation under vivid, red-orange sunrises and sunsets.
Back in the U.S., electricity networks begin failing. Warnings had not been heeded that damp ash conducts electricity, short circuiting power lines and substations. Ash clogs machinery and generator intakes. Its weight damages cables and weaker structures.
Infrastructure damage at Hebgen Lake due to the 7.2 magnitude earthquake of 1959. Image via I.J. Witkind. USGS Photographic Library/ Wikipedia.
As electricity fails, so do water pumps, sewage treatment, heating systems, fuel stations and mobile phone and internet networks. People are scared and supermarket shelves empty nationwide as regional and national supply chains begin to break down.
T+2 weeks
Over the following weeks, the crisis becomes one of survival. Repeated ashfall blocks roads, overwhelms drainage systems and damages roofs. During rain, dry ash turns into a dense slurry that makes clearance work harder. Airports remain closed or severely disrupted across much of North America, while railways, freight depots and farms struggle to operate. Livestock and crops die where pasture and water supplies are buried or contaminated by ash.
Large areas close to Yellowstone remain evacuated, while across the U.S., shelter, fuel, food and clean water become increasingly scarce. Some countries airlift or airdrop humanitarian relief supplies. But they are also concerned about stockpiling for themselves. Losses to agriculture, transport and insurance — with many other businesses and services closed — could lead Canada, Mexico and most Caribbean and Central American countries to declare states of emergency. This is partly due to direct impacts on those countries and partly due to disruption across the U.S. and people fleeing from it.
T+4 months
Several months later, eruptions have weakened to intermittent explosions, but the threat of renewed activity remains. For millions, the disaster is far from over. Dry, windy days lift ash back into the air, while rain and snow turn it into a heavy deposit blocking drains and damaging infrastructure. Eye and throat irritation are widespread. People with asthma and other respiratory conditions face serious health risks under reduced and overworked health services.
Water treatment and power plants struggle with ash contamination, equipment failures, lack of spare parts and overwhelming demand, disrupting essential medical and industrial processes. Crops across the most heavily affected regions have been buried. The loss of American and Canadian grain, maize and soya exports drives global food prices upwards.
Flights gradually resume in less affected areas, but airports across North America repeatedly close whenever winds remobilize the ash. The unreliable airspace and transport networks — coupled with agricultural losses, business disruption and reconstruction costs — trigger banking and insurance crises, producing a global recession.
Meanwhile, the atmospheric effects become global. Most volcanic ash has fallen out, but sulfur dioxide injected into the stratosphere produces sulphate aerosols which reflect a significant proportion of the sun’s energy. Scientists call it a “volcanic cooling episode,” avoiding the term “a new ice age”. Modelling suggests it’s unlikely to cool the global average by more than about 1.5°C, although particular regions and seasons could experience much larger changes. Notably, central North America remains far cooler than before the eruption.
T+10 years
In the years following the eruption, the world moves into long-term recovery and rebuilding. People across the world adapt to a more agrarian lifestyle, learning to fill the land with root vegetables, grains and legumes. With far less leisure time and diminished income, recreational facilities are turned over to food production, notably small-scale greenhouses and vertical farming for producing varied fruits, vegetables, nuts and legumes.
Livestock decreases due to lack of land and feed, opening up more space for crops. People still eating meat typically either hunt big game or trap smaller birds and mammals. Insect farming tends to dominate the re-establishment of bird or mammal farms. People living near coasts, rivers and lakes ramp up fishing, depleting stocks rapidly until controls are enacted in some locations, along with increased farming for seaweed. Where rules are not agreed or enforced, starvation and migration are rampant.
Freshwater availability varies. The world’s climate has changed, providing ample rainfall in some places while drying out others. Large-scale water treatment technology remains known and used. But supply lines for chemicals and spare parts are unreliable. Many people develop local approaches and manage while others suffer contaminated water and disease, including cholera, dengue fever and malaria, just as billions did before the eruption.
Before the eruption, around 4.4 billion people from the world’s population of 8.3 billion lacked full, safe freshwater access. A decade after the eruption, it’s possible that 4.8 billion people lack such freshwater, while the world’s population may have declined to 7.9 billion due to spikes in elderly and infant mortality.
For the eruption’s survivors, disease and death are still rising. The eruption may well provide substantive, long-term evidence for the carcinogenic level of silica in the ash. A small but statistically significant increase in diagnoses of both silicosis (an irreversible lung disease) and lung cancer appears from exposure to ash, with similar results for cardiovascular disease in people breathing in ash particles.
Rates are likely higher than measured, because health systems across a continent were knocked out by the eruption and struggling to recover ten years later. The worst part is that the lack of health systems means that many who are diagnosed cannot be treated properly. Survivable diagnoses become lethal.
Inside the eruption zone, two decades follow of a grey landscape. It appears almost lifeless, with the ash transformed into raging mudflows called lahars in every storm. But vegetation, starting with grasslands and shifting to forests, creeps back into the swathes wiped out in the explosion and people follow. These new pioneers coax the landscape into fertile framing, helping to feed hungry populations.
A lahar travels down a river valley in Guatemala near the Santa María volcano, 1989. Image via Wikipedia/ USGS geologist Jeff Marso.
The dispersed ash eventually settles out of the atmosphere. That permits the sun’s rays to shine fully on the surface again, reviving agriculture and ecosystems. It also revives fears of human-caused climate change, despite the volcano-induced reduction in greenhouse gas emissions. Scientists work hard to determine whether the global climate has been knocked onto a new trajectory — which might be better or worse for human beings — or whether the heat stored in the atmosphere and oceans from humanity’s greenhouse gas burning will once again force a rapidly heating globe.
Additionally, scientists want to calculate deaths, injuries and loss to quality of life. Excess mortality analyses could suggest 0.7-1.3 billion premature deaths due to the eruption and its impacts. Perhaps double that number experienced temporary or permanent health effects but survived, although some will say that 100% of humanity was directly affected.
The good news, at least for our species, is that this unstoppable power of volcanism changed the planet, but did not end humanity … or come close to doing so.
T+1 million years
A creature descends to Earth from a sleek spacecraft, still humanoid but far removed from its ancestor species Homo sapiens sapiens. Tjjze (the pronoun used) has absorbed all the scant information available about ancient “Earth” and is curious to learn more.
The most notable material is the rise of its first technological civilization just over a million years ago. This was followed by the species abandoning the planet as it changed 140,000-160,000 years ago — becoming taller, sleeker, with longer limbs, and with larger hands, heads and brains — having already established itself around the galaxy. In the remaining lore, myths recur of episodes of runaway planetary temperature changes, hot and cold, as well as a series of volcanic blasts that changed the globe.
Tjjze observes that the vegetation is lush and the H2O is plentiful. It provides ample food and water for the bizarre animals and ecosystems. A rapid scan reveals much below the surface. In fact, a large roughly ellipse-shaped ridge made of rock appears prominently underneath the top layers. Yes, this particular region, about 24.3 cqurzots in radius, is definitely lower than the vast plains outside the depression. This seems to indicate an ancient volcanic eruption. And to leave a scar this big, it must have been gigantic.
Tjjze warps the equivalent of the face into the equivalent of a frown as more data are revealed. Indeed, this definitely looks like a caldera. And the age is coming in at around a million years (plus/minus).
Could it have erupted during the time of the technological civilization? Or were they lucky to have just missed it? It is impossible to really know.
Bottom line: Yellowstone has undergone three massive super-eruptions in the past. If the Yellowstone supervolcano erupted today, would humanity survive?
View at EarthSky Community Photos. | Kevin O’Donnell captured this image on December 4, 2025, and wrote: “Part of a timelapse captured during the Cold Moon Supermoon rising over the North Phoenix mountains.” Thank you, Kevin! The Cold Moon is one of the North American full moon names.
Cultures across the world have given special names to full moons, and this practice is very much alive in North America. Some almanacs assign full moon names by the month. On the other hand, other almanacs like to reference full moons relative to seasonal markers, as defined by equinoxes and solstices. Is one way better than the other? No. Both have their roots in folklore. Also, lists of full moon names vary widely coming from different regions and cultures.
Below, we list the most commonly used full moon names in North America. Most of these names were derived from Old English and/or Native American sources. We list them first by the month, and then by the season. Around the middle of this post, we talk about Blue Moons. Toward the bottom, we have a word about moon names in the Southern Hemisphere.
North American full moon names by month
Different Native American tribes, European cultures, and colonial almanacs had their own naming systems, so there’s some overlap and variation between months depending on the source. Here are the most widely recognized full moon names followed by some other traditional names.
January: The most recognized name is Wolf Moon, which is rooted in Native American and European folklore and tied to the howling of hungry wolves during the depths of winter. Other names include:
Moon After Yule – referencing its position just after the Christmas/Yule season
Old Moon – an older English name
Cold Moon – used by some cultures for January’s moon, though this name is more often applied to December in the Algonquin tradition
Ice Moon – reflecting the frozen conditions of midwinter
Snow Moon – occasionally used for January, though it’s more commonly associated with February
February: The most common name today is Snow Moon, reflecting the heavy snowfall typical of February in many parts of North America. Other names include:
Hunger Moon – referencing the scarcity of food and difficult hunting conditions during late winter
Storm Moon – used in some European traditions for the harsh weather this time of year
Ice Moon – another nod to the cold, icy conditions
Bald Eagle Moon – used by the Cree, marking the time when bald eagles begin to appear
Bear Moon – used by the Ojibwe, tied to the time when bear cubs are born during hibernation
Groundhog Moon – a lighter, more modern nickname referencing Groundhog Day
March: March’s full moon is best known as the Worm Moon. It’s traditionally linked to earthworms reappearing in thawing soil as spring approaches, though some sources tie it instead to beetle larvae emerging from bark. Other names include:
Sap Moon – referencing the time when maple sap starts flowing and syrup-tapping season begins
Crow Moon – used by some Native American tribes, marking the return of cawing crows as a sign of winter’s end
Lenten Moon – a European Christian name tied to the season of Lent
Crust Moon – referencing the crusty texture of snow that thaws by day and refreezes at night
Sugar Moon – another reference to maple sugaring season
Chaste Moon – an older European name symbolizing purity, tied to the approach of spring
April: The full moon in April is most commonly known as the Pink Moon. Despite the name, it doesn’t refer to the moon’s actual color. It’s named after Phlox subulata (moss pink or wild ground phlox), one of the first wildflowers to bloom in early spring. Other names include:
Sprouting Grass Moon – referencing new plant growth as the weather warms
Egg Moon – tied to springtime and the symbolism of eggs, often associated with Easter
Fish Moon – used by some coastal tribes, marking the time when shad and other fish swim upstream to spawn
Pesach/Passover Moon – reflecting timing near the Jewish holiday of Passover, which is tied to the lunar calendar
Seed Moon – referencing the start of spring planting season
Breaking Ice Moon – used in some Northern traditions for the thawing of frozen waterways
May: The May full moon is best known as the Flower Moon. It reflects the abundance of blooming flowers across North America in May. Other names include:
Corn Planting Moon – marking the time when corn was traditionally sown
Milk Moon – a European name referencing livestock giving abundant milk during this fertile season
Mother’s Moon – another nod to the fertility and abundance associated with springtime
Hare Moon – a European name tied to the increased visibility of hares (rabbits) during breeding season
Bright Moon – referencing the clearer, longer nights of late spring
Frog Moon – used by some tribes, marking the time when frogs become active and vocal
June: The June full moon is most widely known as the Strawberry Moon. It marks the short strawberry harvesting season in North America, used by Algonquin and other tribes. Other names include:
Rose Moon – a European name referencing roses blooming in early summer
Hot Moon – reflecting the arrival of summer heat
Mead Moon – tied to the tradition of harvesting honey and fermenting mead around this time (this is also linked to the origin of the term “honeymoon”)
Honey Moon – another reference to honey harvesting season, when hives were typically at their fullest
Green Corn Moon – used by some tribes, referencing early corn growth
Planting Moon – used in some traditions to mark ongoing summer planting
July: The July full moon is most commonly known as the Buck Moon. It references the time when male deer (bucks) begin growing new antlers, covered in velvety fur. Other names include:
Thunder Moon – tied to the frequent summer thunderstorms in July
Hay Moon – reflecting the timing of hay harvesting season
Wort Moon – an old European name referring to the time for gathering herbs (“wort” being an old word for plant or herb)
Salmon Moon – used by some coastal and Pacific Northwest tribes, marking the time when salmon swim upstream
Feather Moulting Moon – used by the Cree, referencing the time when birds molt their feathers
Halfway Summer Moon – used by some tribes to mark the midpoint of the summer season
August: The August full moon is best known as the Sturgeon Moon. It’s named for the large sturgeon fish that were most easily caught in the Great Lakes and other major bodies of water during this time. Other names include:
Grain Moon – referencing the harvesting of grain crops in late summer
Red Moon – tied to the reddish appearance the moon can take on due to summer haze near the horizon
Green Corn Moon – used by some tribes to mark ripening corn (though this name is also sometimes used for June or July)
Fruit Moon – reflecting the ripening of fruit as late summer approaches
Barley Moon – a European name marking barley harvest time
Dog Moon – referencing the “dog days of summer,” tied to the star Sirius (the “Dog Star”) being prominent in the sky this time of year
September: The September full moon is often the Harvest Moon, or the full moon closest to the autumn equinox. It was valued for its bright light that let farmers harvest crops into the night. Other names include:
Corn Moon – used when the Harvest Moon falls in October instead, since September’s moon then takes this name, marking the time when corn is traditionally harvested
Barley Moon – a European name referencing the barley harvest, tied to the need to gather and thresh grain before the weather turned
Fruit Moon – reflecting the ripening of fruits like apples and grapes in early autumn
Full Corn Moon – another variation emphasizing the timing with corn harvesting
October: The October full moon is best known as the Hunter’s Moon, which follows the Harvest Moon. This name reflects the time when hunters would track and store meat for winter, taking advantage of the bright moonlight and fields cleared after harvest. Other names include:
Harvest Moon – when it is closest to the fall equinox
Blood Moon – tied to the hunting and slaughtering season, and also to the reddish hue the moon can take on this time of year (note: this is different from the astronomical “blood moon” during a lunar eclipse)
Travel Moon – referencing the migration of animals and, in some traditions, people preparing for winter
Dying Grass Moon – used by some tribes, marking the time when grasses turn brown and die back as autumn deepens
Sanguine Moon – another reference to the reddish coloring associated with this time of year
November: The November full moon is best known as the Beaver Moon. It has two possible origins: either referencing the time when beavers become most active building winter dams before the water freezes, or the time when it was traditional to set beaver traps to secure warm furs for winter. Other names include:
Frost Moon – reflecting the arrival of harder, more consistent frosts
Mourning Moon – a European name reflecting the darkening days and approach of winter
Dark Moon – another reference to the shorter days and longer nights of late autumn
Digging/Scratching Moon – used by some tribes, referencing animals foraging for food before winter sets in
December: The December full moon is best known as the Cold Moon. It reflects the arrival of winter’s deep cold as the year draws to a close. Other names include:
Long Night Moon – referencing the winter solstice, when nights are at their longest
Moon Before Yule – a European name marking the time just before the Yule/Christmas season
Oak Moon – another European name, tied to the significance of oak trees in winter solstice traditions
Snow Moon – occasionally used for December in some traditions, though it’s more commonly associated with February
Full Cold Moon – another variation emphasizing the depth of winter’s chill
Sometimes February doesn’t have a full moon
About once every 19 years, February has no full moon at all. The last time that happened was in 2018. The next time February won’t have a full moon is 2037.
After the winter solstice:
Old Moon or Moon After Yule
Snow Moon, Hunger Moon or Wolf Moon
Worm Moon, Sap Moon, Crow Moon or Lenten Moon
After the spring equinox:
Grass Moon or Egg Moon
Planting Moon or Milk Moon
Rose Moon, Flower Moon or Strawberry Moon
After the summer solstice:
Thunder Moon or Hay Moon
Green Corn Moon or Grain Moon
Fruit Moon or Harvest Moon
After the autumnal equinox:
Harvest Moon or Hunter’s Moon
Hunter’s Moon, Frosty Moon or Beaver Moon
Moon Before Yule or Long Night Moon
Full moon names in the Southern Hemisphere?
As you probably know, the seasons for Earth’s two hemispheres are opposite. When it’s summer in the Northern Hemisphere, it’s winter in the Southern Hemisphere, and so on. When we originally published this article, we suggested that the full moon names might be likewise reversed. For example, the Green Corn Moon or Grain Moon — moon name for the August full moon in North American skylore — might work for the February full moon in the Southern Hemisphere.
But assigning full moon names to moons in the Southern Hemisphere in that way — by flipping the names around to match the seasons — doesn’t really work. For example, our name for January’s full moon in North American skylore is often given as the Wolf Moon. You wouldn’t expect a Wolf Moon for the Southern Hemisphere, because what most of us think of as a “wolf” — a gray wolf, Canis lupus — isn’t native to the Southern Hemisphere.
Unfortunately, it’s difficult to find records of moon names used in the Southern Hemisphere. We asked several EarthSky friends in the Southern Hemisphere if they knew of full moon names for that part of the world, but they all said no. We did find some full moon names for the large island of New Guinea, near Australia, and for South Africa at the website LunarPhasePro.com, but we’ve been unable to establish if those names are still in use today. Check them out if you’re interested!
What about Blue Moons?
Blue Moons are a special case, whether they come by the month or by the season. Sky watchers in recent years have come to recognize both calendar-month and seasonal Blue Moons.
Calendar-month Blue Moons
Calendar-month Blue Moons happen when two full moons fall within a single calendar month. The second of the month’s two full moons is popularly called a Blue Moon. This sort of Blue Moon happens seven times in every 19 years. And we had a calendar Blue Moon on May 31, 2026. As a matter of fact, it’s the most distant full micromoon of 2026.
Let’s take a look at the eight calendar-month Blue-Moons in the present 19-year Metonic cycle:
March 31, 2018
October 31, 2020
August 31, 2023
May 31, 2026
December 31, 2028
September 30, 2031
July 31, 2034
January 31, 2037
Also, in a year where February has no full moon at all, as in the year 2018, you can have two full moons in January and two full moons in March. Thus, during those years there are two Blue Moons in single year. The next time we have two Blue Moons in one year is 2037.
Seasonal Blue Moons
Seasonal Blue Moons happen seven times in 19 years, too. There are usually three full moons between an equinox and a solstice, or vice versa. But sometimes four full moons fall in a single season. In that case, the third of a season’s four full moons is the Blue Moon. The last Blue Moon by this definition happened on August 19, 2024. The next seasonal Blue Moon is May 20, 2027. The seven seasonal Blue Moons in the current 19-year lunar cycle are:
Full moon photos from our EarthSky Community Photos
View at EarthSky Community Photos. | Teresa Molinaro captured this image on November 5, 2025, from Italy and wrote: “The November full moon rises above the sea, bathed in the twilight colors of the Earth’s shadow on the atmosphere and the rosy Belt of Venus.” Thank you, Teresa!View at EarthSky Community Photos. | Cecille Kennedy captured this image on October 7, 2025, from Oregon and wrote: “Harvest Super Moon setting at Pirate Cove with the Belt of Venus colors.” Thank you, Cecille!
Bottom line: North American full moon names, listed first by month and then by season.
View at EarthSky Community Photos. | Kevin O’Donnell captured this image on December 4, 2025, and wrote: “Part of a timelapse captured during the Cold Moon Supermoon rising over the North Phoenix mountains.” Thank you, Kevin! The Cold Moon is one of the North American full moon names.
Cultures across the world have given special names to full moons, and this practice is very much alive in North America. Some almanacs assign full moon names by the month. On the other hand, other almanacs like to reference full moons relative to seasonal markers, as defined by equinoxes and solstices. Is one way better than the other? No. Both have their roots in folklore. Also, lists of full moon names vary widely coming from different regions and cultures.
Below, we list the most commonly used full moon names in North America. Most of these names were derived from Old English and/or Native American sources. We list them first by the month, and then by the season. Around the middle of this post, we talk about Blue Moons. Toward the bottom, we have a word about moon names in the Southern Hemisphere.
North American full moon names by month
Different Native American tribes, European cultures, and colonial almanacs had their own naming systems, so there’s some overlap and variation between months depending on the source. Here are the most widely recognized full moon names followed by some other traditional names.
January: The most recognized name is Wolf Moon, which is rooted in Native American and European folklore and tied to the howling of hungry wolves during the depths of winter. Other names include:
Moon After Yule – referencing its position just after the Christmas/Yule season
Old Moon – an older English name
Cold Moon – used by some cultures for January’s moon, though this name is more often applied to December in the Algonquin tradition
Ice Moon – reflecting the frozen conditions of midwinter
Snow Moon – occasionally used for January, though it’s more commonly associated with February
February: The most common name today is Snow Moon, reflecting the heavy snowfall typical of February in many parts of North America. Other names include:
Hunger Moon – referencing the scarcity of food and difficult hunting conditions during late winter
Storm Moon – used in some European traditions for the harsh weather this time of year
Ice Moon – another nod to the cold, icy conditions
Bald Eagle Moon – used by the Cree, marking the time when bald eagles begin to appear
Bear Moon – used by the Ojibwe, tied to the time when bear cubs are born during hibernation
Groundhog Moon – a lighter, more modern nickname referencing Groundhog Day
March: March’s full moon is best known as the Worm Moon. It’s traditionally linked to earthworms reappearing in thawing soil as spring approaches, though some sources tie it instead to beetle larvae emerging from bark. Other names include:
Sap Moon – referencing the time when maple sap starts flowing and syrup-tapping season begins
Crow Moon – used by some Native American tribes, marking the return of cawing crows as a sign of winter’s end
Lenten Moon – a European Christian name tied to the season of Lent
Crust Moon – referencing the crusty texture of snow that thaws by day and refreezes at night
Sugar Moon – another reference to maple sugaring season
Chaste Moon – an older European name symbolizing purity, tied to the approach of spring
April: The full moon in April is most commonly known as the Pink Moon. Despite the name, it doesn’t refer to the moon’s actual color. It’s named after Phlox subulata (moss pink or wild ground phlox), one of the first wildflowers to bloom in early spring. Other names include:
Sprouting Grass Moon – referencing new plant growth as the weather warms
Egg Moon – tied to springtime and the symbolism of eggs, often associated with Easter
Fish Moon – used by some coastal tribes, marking the time when shad and other fish swim upstream to spawn
Pesach/Passover Moon – reflecting timing near the Jewish holiday of Passover, which is tied to the lunar calendar
Seed Moon – referencing the start of spring planting season
Breaking Ice Moon – used in some Northern traditions for the thawing of frozen waterways
May: The May full moon is best known as the Flower Moon. It reflects the abundance of blooming flowers across North America in May. Other names include:
Corn Planting Moon – marking the time when corn was traditionally sown
Milk Moon – a European name referencing livestock giving abundant milk during this fertile season
Mother’s Moon – another nod to the fertility and abundance associated with springtime
Hare Moon – a European name tied to the increased visibility of hares (rabbits) during breeding season
Bright Moon – referencing the clearer, longer nights of late spring
Frog Moon – used by some tribes, marking the time when frogs become active and vocal
June: The June full moon is most widely known as the Strawberry Moon. It marks the short strawberry harvesting season in North America, used by Algonquin and other tribes. Other names include:
Rose Moon – a European name referencing roses blooming in early summer
Hot Moon – reflecting the arrival of summer heat
Mead Moon – tied to the tradition of harvesting honey and fermenting mead around this time (this is also linked to the origin of the term “honeymoon”)
Honey Moon – another reference to honey harvesting season, when hives were typically at their fullest
Green Corn Moon – used by some tribes, referencing early corn growth
Planting Moon – used in some traditions to mark ongoing summer planting
July: The July full moon is most commonly known as the Buck Moon. It references the time when male deer (bucks) begin growing new antlers, covered in velvety fur. Other names include:
Thunder Moon – tied to the frequent summer thunderstorms in July
Hay Moon – reflecting the timing of hay harvesting season
Wort Moon – an old European name referring to the time for gathering herbs (“wort” being an old word for plant or herb)
Salmon Moon – used by some coastal and Pacific Northwest tribes, marking the time when salmon swim upstream
Feather Moulting Moon – used by the Cree, referencing the time when birds molt their feathers
Halfway Summer Moon – used by some tribes to mark the midpoint of the summer season
August: The August full moon is best known as the Sturgeon Moon. It’s named for the large sturgeon fish that were most easily caught in the Great Lakes and other major bodies of water during this time. Other names include:
Grain Moon – referencing the harvesting of grain crops in late summer
Red Moon – tied to the reddish appearance the moon can take on due to summer haze near the horizon
Green Corn Moon – used by some tribes to mark ripening corn (though this name is also sometimes used for June or July)
Fruit Moon – reflecting the ripening of fruit as late summer approaches
Barley Moon – a European name marking barley harvest time
Dog Moon – referencing the “dog days of summer,” tied to the star Sirius (the “Dog Star”) being prominent in the sky this time of year
September: The September full moon is often the Harvest Moon, or the full moon closest to the autumn equinox. It was valued for its bright light that let farmers harvest crops into the night. Other names include:
Corn Moon – used when the Harvest Moon falls in October instead, since September’s moon then takes this name, marking the time when corn is traditionally harvested
Barley Moon – a European name referencing the barley harvest, tied to the need to gather and thresh grain before the weather turned
Fruit Moon – reflecting the ripening of fruits like apples and grapes in early autumn
Full Corn Moon – another variation emphasizing the timing with corn harvesting
October: The October full moon is best known as the Hunter’s Moon, which follows the Harvest Moon. This name reflects the time when hunters would track and store meat for winter, taking advantage of the bright moonlight and fields cleared after harvest. Other names include:
Harvest Moon – when it is closest to the fall equinox
Blood Moon – tied to the hunting and slaughtering season, and also to the reddish hue the moon can take on this time of year (note: this is different from the astronomical “blood moon” during a lunar eclipse)
Travel Moon – referencing the migration of animals and, in some traditions, people preparing for winter
Dying Grass Moon – used by some tribes, marking the time when grasses turn brown and die back as autumn deepens
Sanguine Moon – another reference to the reddish coloring associated with this time of year
November: The November full moon is best known as the Beaver Moon. It has two possible origins: either referencing the time when beavers become most active building winter dams before the water freezes, or the time when it was traditional to set beaver traps to secure warm furs for winter. Other names include:
Frost Moon – reflecting the arrival of harder, more consistent frosts
Mourning Moon – a European name reflecting the darkening days and approach of winter
Dark Moon – another reference to the shorter days and longer nights of late autumn
Digging/Scratching Moon – used by some tribes, referencing animals foraging for food before winter sets in
December: The December full moon is best known as the Cold Moon. It reflects the arrival of winter’s deep cold as the year draws to a close. Other names include:
Long Night Moon – referencing the winter solstice, when nights are at their longest
Moon Before Yule – a European name marking the time just before the Yule/Christmas season
Oak Moon – another European name, tied to the significance of oak trees in winter solstice traditions
Snow Moon – occasionally used for December in some traditions, though it’s more commonly associated with February
Full Cold Moon – another variation emphasizing the depth of winter’s chill
Sometimes February doesn’t have a full moon
About once every 19 years, February has no full moon at all. The last time that happened was in 2018. The next time February won’t have a full moon is 2037.
After the winter solstice:
Old Moon or Moon After Yule
Snow Moon, Hunger Moon or Wolf Moon
Worm Moon, Sap Moon, Crow Moon or Lenten Moon
After the spring equinox:
Grass Moon or Egg Moon
Planting Moon or Milk Moon
Rose Moon, Flower Moon or Strawberry Moon
After the summer solstice:
Thunder Moon or Hay Moon
Green Corn Moon or Grain Moon
Fruit Moon or Harvest Moon
After the autumnal equinox:
Harvest Moon or Hunter’s Moon
Hunter’s Moon, Frosty Moon or Beaver Moon
Moon Before Yule or Long Night Moon
Full moon names in the Southern Hemisphere?
As you probably know, the seasons for Earth’s two hemispheres are opposite. When it’s summer in the Northern Hemisphere, it’s winter in the Southern Hemisphere, and so on. When we originally published this article, we suggested that the full moon names might be likewise reversed. For example, the Green Corn Moon or Grain Moon — moon name for the August full moon in North American skylore — might work for the February full moon in the Southern Hemisphere.
But assigning full moon names to moons in the Southern Hemisphere in that way — by flipping the names around to match the seasons — doesn’t really work. For example, our name for January’s full moon in North American skylore is often given as the Wolf Moon. You wouldn’t expect a Wolf Moon for the Southern Hemisphere, because what most of us think of as a “wolf” — a gray wolf, Canis lupus — isn’t native to the Southern Hemisphere.
Unfortunately, it’s difficult to find records of moon names used in the Southern Hemisphere. We asked several EarthSky friends in the Southern Hemisphere if they knew of full moon names for that part of the world, but they all said no. We did find some full moon names for the large island of New Guinea, near Australia, and for South Africa at the website LunarPhasePro.com, but we’ve been unable to establish if those names are still in use today. Check them out if you’re interested!
What about Blue Moons?
Blue Moons are a special case, whether they come by the month or by the season. Sky watchers in recent years have come to recognize both calendar-month and seasonal Blue Moons.
Calendar-month Blue Moons
Calendar-month Blue Moons happen when two full moons fall within a single calendar month. The second of the month’s two full moons is popularly called a Blue Moon. This sort of Blue Moon happens seven times in every 19 years. And we had a calendar Blue Moon on May 31, 2026. As a matter of fact, it’s the most distant full micromoon of 2026.
Let’s take a look at the eight calendar-month Blue-Moons in the present 19-year Metonic cycle:
March 31, 2018
October 31, 2020
August 31, 2023
May 31, 2026
December 31, 2028
September 30, 2031
July 31, 2034
January 31, 2037
Also, in a year where February has no full moon at all, as in the year 2018, you can have two full moons in January and two full moons in March. Thus, during those years there are two Blue Moons in single year. The next time we have two Blue Moons in one year is 2037.
Seasonal Blue Moons
Seasonal Blue Moons happen seven times in 19 years, too. There are usually three full moons between an equinox and a solstice, or vice versa. But sometimes four full moons fall in a single season. In that case, the third of a season’s four full moons is the Blue Moon. The last Blue Moon by this definition happened on August 19, 2024. The next seasonal Blue Moon is May 20, 2027. The seven seasonal Blue Moons in the current 19-year lunar cycle are:
Full moon photos from our EarthSky Community Photos
View at EarthSky Community Photos. | Teresa Molinaro captured this image on November 5, 2025, from Italy and wrote: “The November full moon rises above the sea, bathed in the twilight colors of the Earth’s shadow on the atmosphere and the rosy Belt of Venus.” Thank you, Teresa!View at EarthSky Community Photos. | Cecille Kennedy captured this image on October 7, 2025, from Oregon and wrote: “Harvest Super Moon setting at Pirate Cove with the Belt of Venus colors.” Thank you, Cecille!
Bottom line: North American full moon names, listed first by month and then by season.
View larger. | Artist’s concept of Elias 2-24 b, a baby exoplanet less than a million years old. It sits within a prominent gap in the disk of gas and dust surrounding its star. And it’s pulling in material from this disk. Image via W. M. Keck Observatory/ Adam Makarenko/ NASA.
Planets start their lives as “babies,” just like we do. Now scientists have discovered the youngest-known exoplanet so far, Elias 2-24 b.
Elias 2-24 b is less than a million years old, making it a definite cosmic infant.
The planet is still wrapped in the disk of dust and gas that surrounds its star.
Astronomers have discovered exoplanets — worlds orbiting other stars — in a wide range of sizes, masses and ages. That includes some planets that are very young, still forming in the disks of debris around their stars. Now, researchers have found the youngest-known exoplanet so far.
The research team said on September 16, 2026, that the baby planet — called Elias 2-24 b — is less than a million years old. And it is about twice as massive as Jupiter and 450 light-years from Earth.
Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, led the study that found the new baby exoplanet. The study focused on archival observations of seven stars that were observed by the W.M. Keck Observatory in Hawaii. All of these stars are young, with disks of ice, dust and rocky debris still surrounding them. In fact, it is in these protoplanetary disks that new planets are born.
Until now, four other planets have held the record for youngest-known planets. Co-author Lucas Cieza at the Instituto de Estudios Astrofísicos in Chile said:
Our planet-formation models already struggled to explain the previous record holders for the youngest known planet — a four-way tie between two planets orbiting the star PDS 70 and two planets orbiting the star WISPIT 2 — which are all more than 5 million years old. Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes.
The peer-reviewed findings were published in The Astrophysical Journal Letters on September 16, 2026.
Planets in the gaps
Protoplanetary disks will often have gaps within them. It’s baby planets that create these gaps as they gravitationally collect ice, dust and rock from the disk material around them while forming. And just like people, they grow over time and get bigger. Eventually, they become full planets.
The researchers used the coronagraph on the Keck telescope to block out the light coming from the stars. Then they can search for fainter planets. Bernardi said:
The planets should be found within the gaps, since they are carving them. And that’s exactly where we found Elias 2-24 b.
Most of the exoplanets that astronomers discover are already billions of years old. Newborn planets are more difficult to identify. That’s because they are still surrounded by a lot of dust or a long way out from their star. As Cieza explained:
The galaxy churns out new stars and planets continuously, so there are many in every stage of evolution. That means we can see the entire process in theory, but there is a large gap in what most telescopes can detect. We are mostly blind to these baby planets right now.
This is an artist’s animation of Elias 2-24 b. It shows the exoplanet still growing within the disk of gas and dust surrounding its young host star. Material from the disk is actively accreting onto the Jupiter-mass planet. The planet created a prominent gap in the disk. Video via W. M. Keck Observatory/ Adam Makarenko.
Closeup of another newborn exoplanet, WISPIT 2c, which orbits far closer to its star than WISPIT 2b. Image via ESO/ C. Lawlor, R. F. van Capelleveen et al.
Solving a decades-old mystery
About 10 years ago, ALMA (Atacama Large Millimeter/submillimeter Array) in Chile had observed Elias 2-24 b. The telescope had detected a gap in the protoplanetary disk, and what seemed to be a tiny dot of light within it. But, at the time, astronomers weren’t sure what that dot was. Was it a planet? It behaved like a forming planet.
But according to current planet formation theories, it takes about 5 million years for a Jupiter-sized planet to form at Jupiter’s distance from the sun (more than five times the distance of Earth from the sun). Yet the dot was about 55 times farther from its star than Earth is from the sun.
Therefore, researchers looked for previous possible detections of the dot in the Keck Observatory Archive. And they found it, in observations from 2018 and 2020. This allowed the researchers to analyze the dot’s motion over time. And indeed, it moved like a planet would. Bernardi said:
We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together. Elias 2-24 b is at the limit of what current telescopes can detect, but with new instruments like NASA’s Nancy Grace Roman Space Telescope, such detections should become easier.
So the discovery bodes well for future detections of newborn planets, as Cieza noted:
This is just the beginning of a new era of discovery. It’s incredible that with modern technology, we are actually able to see planet formation in action, and Roman will take planet hunting to the next level.
Last year, scientists said that another baby exoplanet, TOI 1227 b, is slowly losing its atmosphere. The atmosphere will be completely gone in about a billion years and the planet will shrink to about 1/10 of its current size.
Bottom line: Astronomers have discovered the youngest-known exoplanet so far, Elias 2-24 b. The baby exoplanet is twice the mass of Jupiter and 450 light-years away.
View larger. | Artist’s concept of Elias 2-24 b, a baby exoplanet less than a million years old. It sits within a prominent gap in the disk of gas and dust surrounding its star. And it’s pulling in material from this disk. Image via W. M. Keck Observatory/ Adam Makarenko/ NASA.
Planets start their lives as “babies,” just like we do. Now scientists have discovered the youngest-known exoplanet so far, Elias 2-24 b.
Elias 2-24 b is less than a million years old, making it a definite cosmic infant.
The planet is still wrapped in the disk of dust and gas that surrounds its star.
Astronomers have discovered exoplanets — worlds orbiting other stars — in a wide range of sizes, masses and ages. That includes some planets that are very young, still forming in the disks of debris around their stars. Now, researchers have found the youngest-known exoplanet so far.
The research team said on September 16, 2026, that the baby planet — called Elias 2-24 b — is less than a million years old. And it is about twice as massive as Jupiter and 450 light-years from Earth.
Andrea Bernardi, a doctoral candidate at the Universidad Diego Portales in Chile, led the study that found the new baby exoplanet. The study focused on archival observations of seven stars that were observed by the W.M. Keck Observatory in Hawaii. All of these stars are young, with disks of ice, dust and rocky debris still surrounding them. In fact, it is in these protoplanetary disks that new planets are born.
Until now, four other planets have held the record for youngest-known planets. Co-author Lucas Cieza at the Instituto de Estudios Astrofísicos in Chile said:
Our planet-formation models already struggled to explain the previous record holders for the youngest known planet — a four-way tie between two planets orbiting the star PDS 70 and two planets orbiting the star WISPIT 2 — which are all more than 5 million years old. Elias 2-24 b shows us that even our best planet-formation models are still missing some important processes.
The peer-reviewed findings were published in The Astrophysical Journal Letters on September 16, 2026.
Planets in the gaps
Protoplanetary disks will often have gaps within them. It’s baby planets that create these gaps as they gravitationally collect ice, dust and rock from the disk material around them while forming. And just like people, they grow over time and get bigger. Eventually, they become full planets.
The researchers used the coronagraph on the Keck telescope to block out the light coming from the stars. Then they can search for fainter planets. Bernardi said:
The planets should be found within the gaps, since they are carving them. And that’s exactly where we found Elias 2-24 b.
Most of the exoplanets that astronomers discover are already billions of years old. Newborn planets are more difficult to identify. That’s because they are still surrounded by a lot of dust or a long way out from their star. As Cieza explained:
The galaxy churns out new stars and planets continuously, so there are many in every stage of evolution. That means we can see the entire process in theory, but there is a large gap in what most telescopes can detect. We are mostly blind to these baby planets right now.
This is an artist’s animation of Elias 2-24 b. It shows the exoplanet still growing within the disk of gas and dust surrounding its young host star. Material from the disk is actively accreting onto the Jupiter-mass planet. The planet created a prominent gap in the disk. Video via W. M. Keck Observatory/ Adam Makarenko.
Closeup of another newborn exoplanet, WISPIT 2c, which orbits far closer to its star than WISPIT 2b. Image via ESO/ C. Lawlor, R. F. van Capelleveen et al.
Solving a decades-old mystery
About 10 years ago, ALMA (Atacama Large Millimeter/submillimeter Array) in Chile had observed Elias 2-24 b. The telescope had detected a gap in the protoplanetary disk, and what seemed to be a tiny dot of light within it. But, at the time, astronomers weren’t sure what that dot was. Was it a planet? It behaved like a forming planet.
But according to current planet formation theories, it takes about 5 million years for a Jupiter-sized planet to form at Jupiter’s distance from the sun (more than five times the distance of Earth from the sun). Yet the dot was about 55 times farther from its star than Earth is from the sun.
Therefore, researchers looked for previous possible detections of the dot in the Keck Observatory Archive. And they found it, in observations from 2018 and 2020. This allowed the researchers to analyze the dot’s motion over time. And indeed, it moved like a planet would. Bernardi said:
We usually hear about telescopes working separately, but this confirmation was possible only by using multiple telescopes together. Elias 2-24 b is at the limit of what current telescopes can detect, but with new instruments like NASA’s Nancy Grace Roman Space Telescope, such detections should become easier.
So the discovery bodes well for future detections of newborn planets, as Cieza noted:
This is just the beginning of a new era of discovery. It’s incredible that with modern technology, we are actually able to see planet formation in action, and Roman will take planet hunting to the next level.
Last year, scientists said that another baby exoplanet, TOI 1227 b, is slowly losing its atmosphere. The atmosphere will be completely gone in about a billion years and the planet will shrink to about 1/10 of its current size.
Bottom line: Astronomers have discovered the youngest-known exoplanet so far, Elias 2-24 b. The baby exoplanet is twice the mass of Jupiter and 450 light-years away.
