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Supervolcanoes

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What would cause such a giant caldera?

You can stand on the rim and view the enormous Yellowstone Caldera, but it's hard to visualize a volcano or a set of eruptions that enormous. Supervolcanoes are a fairly new idea in volcanology. Although their eruptions are unbelievably massive, they are exceedingly rare. The power of Yellowstone, even 640,000 years after the most recent eruption, is seen in its fantastic geysers.

Supervolcanoes

Supervolcano eruptions are extremely rare in Earth's history. It’s a good thing because they are unimaginably large. A supervolcano must erupt more than 1,000 cubic km (240 cubic miles) of material, compared with 1.2 km 3 for Mount St. Helens or 25 km 3 for Mount Pinatubo, a large eruption in the Philippines in 1991. Not surprisingly, supervolcanoes are the most dangerous type of volcano.

Supervolcano Eruptions

The exact cause of supervolcano eruptions is still debated. However, scientists think that a very large magma chamber erupts entirely in one catastrophic explosion. This creates a huge hole or caldera into which the surface collapses ( Figure below ).

The caldera at Santorini in Greece is so large that it can only be seen by satellite.

Yellowstone Caldera

The largest supervolcano in North America is beneath Yellowstone National Park in Wyoming. Yellowstone sits above a hotspot that has erupted catastrophically three times: 2.1 million, 1.3 million, and 640,000 years ago. Yellowstone has produced many smaller (but still enormous) eruptions more recently ( Figure below ). Fortunately, current activity at Yellowstone is limited to the region’s famous geysers.

The Old Faithful web cam shows periodic eruptions of Yellowstone’s famous geyser in real time: http://www.nps.gov/features/yell/live/live4.htm .

The Yellowstone hotspot has produced enormous felsic eruptions. The Yellowstone caldera collapsed in the most recent super eruption.

Supervolcano Eruptions and Life on Earth

A supervolcano could change life on Earth as we know it. Ash could block sunlight so much that photosynthesis would be reduced and global temperatures would plummet. Volcanic eruptions could have contributed to some of the mass extinctions in our planet’s history. No one knows when the next super eruption will be.

Interesting volcano videos are seen on National Geographic Videos, Environment Video, Natural Disasters, Earthquakes: http://video.nationalgeographic.com/video/player/environment/ . One interesting one is “Mammoth Mountain,” which explores Hot Creek and the volcanic area it is a part of in California.

Summary

  • Supervolcano eruptions are rare but massive and deadly.
  • Yellowstone Caldera is a supervolcano that has erupted catastropically three times.
  • Supervolcano eruptions can change the course of life on Earth.

Practice

Use this resource to answer the questions that follow.

1. What is the question at Yellowstone?

2. Why is gravity weaker at Yellowstone?

3. What will be the first indications of an eruption?

4. What is danger zone of a Yellowstone eruption?

5. How far may a pyroclastic flow reach?

6. What problems will the ash cause?

7. What is the deadliest part of the eruption?

8. What would the possible long term effects of an eruption?

Review

1. What is the composition of supervolcano eruptions? Why are these eruptions so massive?

2. What is the source of volcanism for the supervolcano at Yellowstone?

3. How does a supervolcano eruption potentially change the course of life on Earth?

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