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Resurgent Caldera

Resurgent calderas are the largest volcanic structures on Earth. They can be up to 62 miles across. They result from the widespread collapse of vast magma chambers, not from a single volcano. These calderas are produced by incredibly destructive eruptions known as pyroclastic sheet flows.

None of these have happened in historic times. The youngest resurgent caldera is the Toba Caldera on Sumatra, about 74,000 years old. It was formed by the largest volcanic eruption in the last 25 million years. 1,740 cubic miles of debris was ejected. The caldera is 62 miles long and 29 18 miles wide, and is 1,666 feet deep, making it the largest volcanic structure on Earth.

The caldera is now home to Lake Toba and Samosir Island. The island formed from uplift of the caldera floor caused by magma pressure from below. This kind of uplift is common to all resurgent calderas, as new magma fills in the empty magma chamber.

The Yellowstone Caldera, Wyoming, is the result of the Yellowstone Supervolcano. This huge volcano complex erupted about 640,000 years ago. The Yellowstone Caldera is more than 45 miles long. New scientific research has shown the magma chamber measures 55 miles by 20 miles, and is 6 mi deep. This is about the same size it was during its last eruption.