A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. The actual explosivity of these eruptions varies, but the sheer volume of ejected tephra is enough to radically alter the landscape and severely impact global climate for years, with a cataclysmic effect on life.
The term was originally coined by the producers of the BBC popular science program, Horizon, in 2000 to refer to these types of eruption. That investigation brought the subject more into the public eye, leading to further studies of the possible effects. At first, supervolcano was not a technical term used in volcanology, but more recently, in 2003 and 2004, the term has been used in articles. Though there is no well-defined minimum explosive size for a "supervolcano", there are at least two types of volcanic eruption that have been identified as supervolcanoes: massive eruptions and large igneous provinces.
Large igneous provinces
A large igneous province (LIP) is an extensive region of basalts on a continental scale, resulting from flood basalt eruptions. When created, these regions often occupy several million km² and have volumes on the order of 1 million km³. In most cases, the majority of this is laid down over an extended but geologically sudden period of about several million years.
Massive eruptions
Eruptions with a Volcanic Explosivity Index of 8 (VEI-8) are mega-colossal events that eject at least 1000 km³ of pyroclastic material. VEI-8 eruptions are so powerful that they form circular calderas rather than mountains because the downward collapse of land at the eruption site fills emptied space in the magma chamber beneath. The caldera can remain for millions of years after all volcanic activity at the site has ceased.
Known eruptions
VEI-8 volcanic events have included eruptions at the following locations. Estimates of the volume of erupted material are given in parentheses.
- Lake Taupo, North Island, New Zealand - Oruanui eruption 26,500 years ago (1,170 km³)
- Lake Toba, Sumatra, Indonesia - 75,000 years ago (2,800 km³)
- Yellowstone Caldera, Wyoming, United States - 2.2 million years ago (2,500 km³) and 640,000 years ago (1,000 km³)
- La Garita Caldera, Colorado, United States - Source of the truly enormous eruption of the Fish Canyon Tuff 27.8 million years ago (~5,000 km³)
The Lake Toba eruption plunged the Earth into a volcanic winter, eradicating an estimated 60% of the human population (although humans managed to survive even in the vicinity of the volcano), and was responsible for the formation of sulfuric acid in the atmosphere.
Satellite image of Lake Toba.
|
