Questions About Super Volcanoes
What is a supervolcano?
The term "supervolcano" implies a volcanic center that has had an eruption of magnitude 8 on the Volcano Explosivity Index (VEI), meaning the measured deposits for that eruption is greater than 1,000 cubic kilometers (240 cubic miles). The VEI scale was created as a general measurement of the explosivity of an eruption. There are multiple characteristics used to give an eruption its VEI allowing for the classification of current and historic eruptions. The most common criteria are volume of ejecta (ash, pumice, lava) and column height. All VEI 8 eruptions occurred tens of thousands to millions of years ago making the volume of ejecta or deposits the best method for classification. An eruption is classified as a VEI 8 if the measured volume of deposits is greater than 1,000 cubic kilometers (240 cubic miles). Therefore a supervolcano is a volcano that at one point in time erupted more than 1,000 cubic kilometers of deposits. Yellowstone, like many other supervolcanoes, has also had much smaller eruptions. For a comparison of eruption sizes including the three largest Yellowtone eruptions, please see Eruption Size in the VHP Photo Glossary.
What are some other examples of supervolcanoes?
Volcanoes that produced exceedingly voluminous pyroclastic eruptions and formed large calderas in the past 2 million years would include Yellowstone, Long Valley in eastern California, Toba in Indonesia, and Taupo in New Zealand. Other "supervolcanoes" would likely include the large caldera volcanoes of Japan, Indonesia, and South America. The most recent supervolcanic eruption on Earth occurred 74,000 years ago at the Toba Caldera in Sumatra, Indonesia.
I read that scientists couldn't find the Yellowstone caldera until they looked at a photo of Yellowstone from space. Is this true?
Not according to Bob Christiansen. Bob is the USGS scientist who delineated the three Yellowstone calderas and told the world about the great eruptions that formed them. Bob reports that he traced out the caldera boundaries through old fashioned field work... walking around with a hammer and hand lens and looking carefully at the rocks and their distributions. Most of the key observations were made in the 1960s and 1970s. Several authors have written that these large calderas were discovered from space and we suspect that the rumor probably got started because initial field work that delineated them was partly funded by NASA. The idea was to compare well-constrained geologic maps with images taken from space. So Bob's geologic map was used to verify the NASA images, not the other way around.
Also see our Supervolcano docudrama questions and answers page where scientists answer questions about Yellowstone Volcano and the new docudrama.
