Supervolcano

A supervolcano is a volcano capable of producing a volcanic eruption with ejecta greater than 1,000 cubic kilometers (240 cubic miles). This is thousands of times larger than most historic volcanic eruptions. Supervolcanoes can occur when magma in the Earth rises into thecrust from a hotspot but is unable to break through the crust. Pressure builds in a large and growing magma pool until the crust is unable to contain the pressure. They can also form at convergent plate boundaries (for example, Toba) and continental hotspot locations (for example,Yellowstone).

The Discovery Channel highlighted six known supervolcanoes: the Yellowstone, Long Valley, and Valles Caldera in the United States; Lake Toba, North Sumatra, Indonesia; Taupo Volcano, North Island, New Zealand; and Aira Caldera, Kagoshima Prefecture, Kyūshū, Japan. Although there are only a handful of supervolcanoes, supervolcanic eruptions typically cover huge areas with lava andvolcanic ash and cause a long-lasting change to weather (such as the triggering of a small ice age) sufficient to threaten the extinction of species.

Massive explosive eruptions

Eruptions with a Volcanic Explosivity Index of 8 (VEI-8) are colossal events that throw out at least 1,000 km³ Dense Rock Equivalent (DRE) of ejecta; VEI-7 events eject at least 100 km³ (DRE).

VEI-7 or 8 eruptions are so powerful that they often form circular calderas rather than cones because the downward withdrawal of magma causes the overlying mass to collapse and fill the void magma chamber beneath.

One of the classic calderas is at Glen Coe in the Grampian Mountains of Scotland. First described by Clough et al. (1909) its geology and volcanic succession has recently been re-analysed in the light of new discoveries. There is an accompanying 1:25000 solid geology map.

By way of comparison, the 1980 Mount St. Helens eruption was at the lower end of VEI-5 with 1.2 km³, and both Mount Pinatubo in 1991 andKrakatoa in 1883 were VEI-6 with 25 km^3.

Known super eruptions

Estimates of the volume of ejected material are given in parentheses.

VEI 7

VEI-7 volcanic events, less colossal but still supermassive, have occured in the geological past. The only ones in historic times are Tambora, in 1815, Baekdu Mountain, 969 CE (±20 years), and possibly Mount Aso between 300,000 to 80,000 years ago.

Valles Caldera, New Mexico, United States - ~1.15 million years ago (~600 km³)

Aso, Kyūshū, Japan - four large explosive eruptions between 300,000 to 80,000 years ago (last one > 600 km³)

Macauley Island, Kermadec Islands, New Zealand - ~6,300 years ago (~ 4,300 BCE) (100 km³)

Baekdu Mountain, China/North Korea - ~969 CE (96±19 km³)

Tambora, Sumbawa Island, West Nusa Tenggara, Indonesia - 1815 (160 km³), the following year 1816 became known as the "Year Without a Summer"

VEI 8

VEI-8 eruptions have happened in the following locations.

La Garita Caldera, Colorado, United States - Source of the enormous eruption of the Fish Canyon Tuff ~27.8 million years ago (~5,000 km³)

Cerro Galan, Catamarca Province, Argentina - 2.5 million years ago (1,050 km³)

Yellowstone Caldera, Lava Creek Tuff, Wyoming, United States, Yellowstone hotspot - 640,000 years ago (1,000 km³)

Lake Toba, Sumatra, Indonesia - ~74,000 years ago (~2,800 km³)

Lake Taupo, Taupo Volcanic Zone, North Island, New Zealand - Oruanui eruption ~26,500 years ago (~1,170 km³)

source: uncle google & uncle wiki