How Many Super Volcanoes Are There?
QUICK ANSWER
About 20-30 supervolcano sites are known worldwide. These are volcanoes capable of producing eruptions at least 1,000 times larger than typical volcanic activity. Famous supervolcanoes include Yellowstone (US), Toba (Indonesia), Long Valley (California), Taupo (New Zealand), and Campi Flegrei (Italy). None has erupted in modern history.
Supervolcanoes are among the most catastrophic geological hazards on Earth, but they're also extremely rare. Only about 20-30 sites worldwide qualify, defined by having produced super-eruptions at some point in geological history. None has produced a super-eruption in tens of thousands of years, and predictions about when one might erupt are highly uncertain. Most supervolcanoes are quiet at the surface, betraying nothing of their massive size beneath.
What counts as a supervolcano?
A supervolcano is defined by its ability to produce a super-eruption, meaning an eruption that releases at least 1,000 cubic kilometers of material (a Volcanic Explosivity Index, or VEI, of 8). This is at least 1,000 times more than typical volcanic eruptions. Most supervolcanoes don't look like traditional cone-shaped volcanoes; they appear as large depressions called calderas, formed when the volcano's magma chamber collapsed after a super-eruption. The distinction between supervolcano and very large normal volcano is a matter of definition based on the size of past eruptions.
Where are the major supervolcanoes?
The most famous supervolcanoes include Yellowstone in Wyoming (USA), with three major eruptions in the past 2.1 million years. Toba in Indonesia produced one of Earth's largest known eruptions about 74,000 years ago. Long Valley in California erupted 760,000 years ago. Taupo in New Zealand had a massive eruption around 26,500 years ago. Campi Flegrei (Phlegraean Fields) near Naples, Italy is one of the few supervolcanoes near a major population center. Other supervolcano sites are scattered across South America, Africa, and Asia.
When did supervolcanoes last erupt?
Supervolcano eruptions are extremely rare. Toba's eruption 74,000 years ago is the most recent confirmed super-eruption. Before that, Whakamaru in New Zealand erupted about 340,000 years ago. Yellowstone's most recent major eruption was 631,000 years ago. The average interval between super-eruptions globally is roughly 100,000 years, though this is a statistical average from a small sample. No human civilization has ever witnessed a super-eruption, though oral traditions and archaeological evidence suggest the Toba eruption may have affected early human populations significantly.
How dangerous are supervolcano eruptions?
Super-eruptions are among the most devastating natural disasters possible. They release so much material into the atmosphere that they affect global climate for years or decades, causing 'volcanic winters' that can drop global temperatures by several degrees Celsius. Volcanic ash blankets thousands of square miles, potentially burying agricultural land and rendering air unbreathable. Crops fail worldwide due to reduced sunlight and changed weather patterns. The 1815 Tambora eruption (which was much smaller than a true super-eruption) caused 1816 to be the 'Year Without a Summer' worldwide. A true super-eruption would be far worse.
About 20-30 supervolcano sites worldwide are capable of producing massive eruptions thousands of times larger than typical volcanoes. Yellowstone, Toba, Long Valley, Taupo, and Campi Flegrei are the most famous. None has erupted in modern history, with the last super-eruption being Toba 74,000 years ago. The threat is real but extremely rare on human timescales.
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