Photoglossary

Plinian eruption

Plinian eruptions are large explosive events that form enormous dark columns of tephra and gas high into the stratosphere (>11 km). Such eruptions are named for Pliny the Younger, who carefully described the disastrous eruption of Vesuvius in 79 A.D. This eruption generated a huge column of tephra into the sky, pyroclastic flows and surges, and extensive ash fall. Many thousands of people evacuated areas around the volcano, but about 2000 were killed, including Pliny the Older.

Facts and Figures: Large plinian eruptions sometimes result in the withdrawal of so much magma from below a volcano that part of it collapses to form a large depression called a caldera. A few well known plinian eruptions of the 20th century include Mount Spurr, Alaska (June 27, August 18, and September 16-17, 1992); Mount Pinatubo, Philippines (June 15, 1991); El Chichón, Mexico (March-April 1982); Mount St. Helens, Washington (May 18, 1980); Agung volcano, Indonesia (March 17, 1963); and Novarupta, Valley of 10,000 Smokes, Alaska (June 6, 1912). Some plinian eruptions inject such large quantities of aerosols (small liquid droplets) into the stratosphere that surface temperatures on earth may decrease slightly. A few recent eruptions resulted in detectable cooling: the 1991 eruption of Mount Pinatubo, Philippines, and the 1982 eruption of El Chichón, Mexico. The massive 1815 eruption of Mount Tambora volcano, Indonesia, is thought to have caused the 1816 «Year without a Summer» in the northeastern U.S., Canada, and western Europe. In the 21th century plinian eruptions were registered at Chaiten Volcano (Chile, May 2008) and Redoubt Volcano (Alaska, March-April 2009).

A plinian-type eruption from Mount Spurr, Alaska, sent an eruption column to a height of about 18 km above sea level (18.8.1992). Photo: © R. McGimsey

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