Supervolcanoes 101 | National Geographic

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[Narrator] Supervolcanoes are the most violent and complex class of volcanoes. But despite their destructive capabilities, they can also make way for life renewed. Around 20 supervolcanoes are scattered across the planet. They're usually characterized as large depressions in the ground, called calderas, located above multiple openings in the Earth's crust.

In terms of eruptions, supervolcanoes explode at a magnitude of eight, the highest and most violent classification on the Volcanic Explosivity Index. Supervolcanoes undergo a life cycle of three major stages: a surge of trapped magma, a supereruption, and a resurgence. The first stage of a supervolcano's life cycle involves a pocket of magma trapped under the Earth's crust. Called a hotspot, this magma reservoir is fed by a pipeline deep into Earth's molten interior. It grows and builds pressure underground, eventually causing the crust above to be pushed upward.

The supervolcano Campi Flegrei on the west coast of Italy has pushed the ground up several times over the past few decades. At one point, within a matter of only two years, enough magma accumulated to cause the ground to swell up to six and a half feet. The next stage of a supervolcano's life cycle is a supereruption. At this point, the buildup of pressure in a magma reservoir hits a critical mass and then explodes, sending over 1,000 cubic kilometers of tephra, or ash and rocky material, into the sky. The most recent supereruption occurred in New Zealand approximately 26,000 years ago.

The supervolcano Taupo ejected about 1,100 cubic kilometers of tephra into the air, enough material to constitute nearly half a million Great Pyramids of Giza. After a supereruption, a supervolcano undergoes a stage called resurgence. Having dispelled its contents, a supervolcano's magma reservoir collapses and forms a caldera. The Yellowstone Caldera in the United States is currently in resurgence, after a supereruption occurred about 640,000 years ago.

In the time since, freshwater collected in the caldera to form a lake, plants and wildlife returned to reclaim the space, and some of the world's largest geothermal features emerged. Supervolcanoes have created unparalleled natural beauty, all in the wake of some of the world's most cataclysmic events.