Researchers now believe the sprawling Yellowstone caldera was created by two massive eruptions from the supervolcano that occurred approximately 630,000 years ago. Geologists from the University of California Santa Barbara (UCSB) made this discovery when they uncovered new evidence of the two massive eruptions in the Santa Barbara Basin, which was uniquely suited to capture a long-lasting record of volcanic activity. The record suggests these two closely spaced eruptions from the Yellowstone supervolcano altered the planet’s climate in the wake of an ice age and created the 45 x 30 mile Yellowstone caldera that can be seen today.

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The evidence for the two massive eruptions was found in two layers of ash and shell sediments off the coast of Santa Barbara, California. 630,000 years ago, the underwater conditions of the Santa Barbara Basin were ideal for preserving records of volcanic activity because of a nutrient-rich environment which allowed single-celled organisms known as foraminifera to thrive. The microscopic shells of the foraminifera contain temperature-sensitive oxygen isotopes, which allows scientists to determine the temperature of the sea at a particular point in the past.

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Based on the record of foraminifera shells, researchers determined that the Santa Barbara Basin cooled approximately 3 degrees Celsius after each of the super-eruptions, due to ash and volcanic gases in the atmosphere blocking sunlight. Although the world at the time was warming in the wake of an ice age, the two eruptions delayed this climate shift significantly. “It was a fickle, but fortunate time,” said Jim Kennett, geologist and lead author of the study published by the Geological Society of America. “If these eruptions had happened during another climate state we may not have detected the climatic consequences because the cooling episodes would not have lasted so long.”

Via New Atlas

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