Yellowstone supervolcano (image: USGS).

The Yellowstone supervolcano has had three explosive eruptions in history. These occurred 2.1, 1.3 and 0.6 million years ago. The ash fall from these events covered half of the United States. These eruptions most likely caused global temperatures to drop which affected the world’s climate.

Image: Ash fall from the Yellowstone supervolcano in history (source: USGS).

The Yellowstone Supervolcano, Calderas and Ashfalls

These supervolcano eruptions created very large calderas. A caldera is a crater caused by the collapse of the earth’s surface. This is most likely caused by the loss of magma that supported the earth’s surface. The size of these calderas range from 16 to 95 kilometers in length.

Philippines - USA Map The area covered by ash falls were much larger than the calderas. They extended over 1500 kilometers in distance.

For comparison purposes, a map of the Philippines is superimposed on the map of the USA. Ashfall from a supervolcano would have covered the entire Philippines.

Dangers of a Supervolcano

The immediate result of a violent supervolcano eruption would be the explosive blast. This blast is often followed by pyroclastic flows. This is a cloud of rapidly moving hot gas and ash.

Lava flows could also occur. Historically, lava flows are more common than the violent caldera producing eruptions.

With an explosive eruption, ash falls would occur. The ash would modify the environment significantly. On a global scale, changes in the world’s climate could also occur.

Improving Your Reading and Thinking Skills

Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.


How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.


Geology and History, US Geologic Service.


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