Illustrated Volcano Glossary
- VolcanologyPlinian eruption of Mt. St. Helens on May 18, 1980 (USGS Photograph taken on May 18, 1980, by Donald A. Swanson)The most explosive and largest type of volcanic eruptions. Plinian eruptions erupt more than 1 cubic kilometer of magma often within less than a few days and produce ash columns that can reach 20-50 km height.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 2,000 were killed, including Pliny the Older.
- 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.