Yellowstone Volcano: Facts & Frequently Asked Questions

Responsible for the many natural wonders of Yellowstone National Park is an underground supervolcano with the capability of erupting up to 240 cubic meters of lava. The Yellowstone Volcano’s long history of activity has created the tuffs, cliffs, hot springs, geysers, and unique mineral and rock formations that make it one of the most visited destinations in the world. The landscape of the park is truly alive and therefore constantly monitored for volcanic activity and potential earthquakes.

How large is the volcano?

The currently active Yellowstone Caldera (indentation caused by eruption and excretion of internal magma), created by the last eruption, measures about 34 by 45 miles.

Is the volcano still active?

Yes, the thermal activity that causes hot springs and geysers, as well as the high underground temperature (40x more than the above-ground average), proves the volcanos is still active. The presence of earthquakes, about 1,000 to 3,000 per year also attest to its continued activity.

When was the last eruption?

There have been 3 cycles of volcanic events over the last 2.1 million years in Yellowstone. The last one occurred 640,000 years ago over the Yellowstone Plateau. The last lava flow from this eruption happened between 180,000 to 70,000 years ago.

Is another eruption likely?

Scientists have been monitoring the volcano for the past 30 years and believe that another eruption within the next millennium is highly unlikely, though not entirely impossible.

How do scientists know if the volcano will erupt?

Scientists at the Yellowstone Volcano Observatory keep track of earthquake activity, ground deformations, and other indicators of a pending eruption.

How much notice would scientists have of a future eruption?

The build-up to a volcanic eruption is slow and noticeable due to the increase in earthquake and thermal activity. Scientists who constantly observe the Yellowstone Volcano will be able to predict an oncoming eruption within days, weeks, or even years prior to its occurrence.

Are there any hazards to be aware of while visiting the park?

The park’s natural structures are relatively normal and steady, so hazards are unlikely and should only be taken as a precaution. Park notifications of likely anomalies will be conveyed to the public to ensure the safety of guests.

Hydrothermal Explosions: 

  • Hydrothermal Explosions – The release of steam or hot water from hot springs, geysers, and volcanic vents may be caused by earthquakes or pressure from rising lakes or depleting glaciers. The last hydrothermal explosion was in 1989 at Porkchop Geyser in Norris Geyser Basin. The remains of this explosion are still visible today with rock debris surrounding Porkchop’s central spring spanning 15 ft across.

Lava Flow: 

  • Lava Flow – Considering the last lava flow was at least 70,000 years ago, it is unlikely we will see it happen again in our lifetime. However, it is good to know what will happen just in case. When an eruption occurs, it would produce either rhyolite or basalt lava. Rhyolite is thick and highly explosion from trapped gas. Basalt is thinner and less combustible, but moves faster. In either scenario, lava flow would not extend past the park boundaries, however it would cause devastation to anything in its path. The ash and pumice caused by the blasts could extend further well outside the park.

Ash and Rock Debris: 

  • Ash and Rock Debris – The range of ash and rock debris depends on the magnitude of the eruption. The worse-case scenario of a caldera explosion would have extreme effects for the entire planet. It would create a spread of ash up to 6 miles and continue to move outward across the continent then into the atmosphere. The sulfur dioxide that enters the atmosphere could cause temperatures to drop drastically, however this is a very unlikely situation.


  • Earthquakes – The chance of an earthquake in Yellowstone is more likely considering a few thousand occur every year. Usually they are small and almost unnoticeable. Most larger 3 or 4 magnitude earthquakes are caused by tectonic plate movement and usually do not occur in the caldera area since high temperatures keep the rock weak and flexible enough to not break.

How will the park notify guests of a possible eruption?

The park has a 24-hour center that communicates with local media, employees, guests and nearby neighborhoods. Emergency plans are also organized to notify and evacuate affected regions in the event of an eruption.

Where can I find up-to-date data about the volcano?

You can view current data regarding thermal temperatures and locations of earthquakes, as well as view live webcams of the park through the Yellowstone Volcano Observatory’s website here.

Data collected from the park’s ecosystem helps scientists understand the Earth’s geology and provides insight into tracking and predicting natural disasters. This research also ensures that visitors touring Yellowstone national park can safely view the park’s natural wonders without any immediate danger.

Adam Lackner
Adam Lackner
The backcountry is a place of enjoyment for this outdoorsman. Adam spent five years in the Marine Corps before heading for seasonal guiding positions in Alaska, Montana, Colorado, Idaho, Arizona, Mexico, and now Wyoming. “Being where the mountains are big keeps the complaints small!”
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