Wikipedia:Today's featured list/April 17, 2015
The largest volcanic eruptions on Earth can have a major regional or even global impact; some affect the climate and contribute to mass extinctions. In a volcanic eruption, lava, tephra (volcanic bombs, lapilli, and ash), and various gases are expelled from a volcanic vent or fissure. Volcanic eruptions can generally be characterized as either explosive eruptions, sudden ejections of rock and ash, or effusive eruptions, relatively gentle outpourings of lava. Numerous eruptions have produced at least 1,000 km3 (240 cu mi) of lava and tephra; for explosive eruptions, this corresponds to a Volcanic Explosivity Index (or VEI) of 8, at least a thousand times larger than the 1980 eruption of Mount St. Helens, which produced only 1 km3 (0.2 cu mi) of material, and at least six times larger than the 1815 eruption of Mount Tambora, the largest eruption in recent history, which produced 160 km3 (38 cu mi) of volcanic deposits. There have probably been many such eruptions during Earth's history beyond those shown in these lists. However, erosion and plate tectonics have taken their toll, and many eruptions have not left enough evidence for geologists to establish their size. (Full list...)