Lateral eruption

A lateral eruptions or lateral blast is a volcanic eruption which is directed laterally from a volcano rather than upwards from the summit. Lateral eruptions are caused by the outward expansion of flanks due to rising magma.[1] Breaking occurs at the flanks of volcanoes making it easier for magma to flow outward. As magma is pushed upward towards the volcano it diverges towards the flanks before it has a chance to erupt from the crater. When the expanding flank finally gives it releases a flow of magma. More explosive lateral eruptions are referred to as lateral blasts. Some of the most notable examples of a lateral eruption include Mount St. Helens, Mount Pelée, and Mount Etna.[2]

Eruption of Mount St Helens and its deposits.
Present-day Mt. St. Helens, Washington State, USA. The May 18, 1980 eruption of Mt. St. Helens is a well-known example of a lateral eruption.

Creation of a lateral eruption

Most eruptions are caused by the immediate decompression of a magma chamber near the flanks of the volcano. During an eruption, the rapid decompression of magma may cause subsidence of the mountain, and if a flank collapses, a lateral eruption occurs. The directed nature of the blast may cause damage at much greater distances from the peak than a summit eruption would have. Pyroclastic flows and lahars can affect areas originating from the volcano roughly in the shape of a cone that can span hundreds of square kilometers.[3]

Examples

Mount St. Helens is a stratovolcano located in Washington, USA. Volcanic activity beginning in March 1980 saw magma accumulating underneath the mountain's north flank. On May 18, 1980, an earthquake triggered the collapse of the flank and a lateral eruption which killed 57 people. It was the deadliest volcanic event in US history.[4]

Mount Pelée is a volcano located on Martinique, in the Caribbean. It underwent a lateral eruption on May 8, 1902, killing 28,000 people in the deadliest volcanic event of the 20th century.

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References
  1. Schmincke, Hans-Ulrich (2004). Volcanism. Kiel, Germany: Springer-Verlag. ISBN 3-540-43650-2.
  2. Bonaccorso, A.; D’Amico, S.; Mattia, M.; Patanè, D. (2004). "Intrusive Mechanisms at Mt. Etna Forerunning the July-August 2001 Eruption from Seismic and Ground Deformation Data". Pure and Applied Geophysics. 161 (7): 1469–1487. doi:10.1007/s00024-004-2515-4.
  3. Alvarado, Guillermo; Soto, Gerando; Schmincke, Hans-Ulrich; Bolge, Louise; Sumita, Mari (2006). "The 1968 andesitic lateral blast eruption at Arenal volcano, Costa Rica". Journal of Volcanology and Geothermal Research. 157 (1–3): 9–33. doi:10.1016/j.jvolgeores.2006.03.035.
  4. Lipman, Peter W. (1982). The 1980 eruptions of Mount St. Helens, Washington. US Gov. Print. Off. OCLC 313837129.
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