Saturday, May 8, 2010

Plinian Eruption

Plinian eruption is a volcanic eruption which is marked by columns of gas and volcanic ash extending high into the stratosphere, a high layer of the atmosphere. The key characteristics are ejection of large amount of pumice and very powerful continuous gas blast eruptions. Plinian eruptions include the most violent forms of all volcanic activity. These outbursts expel fine ash and pumice, composed of rhyolite, dacite, phonolite, trachyte or andesite often at supersonic speeds.

Short Plinian eruptions can end in less than a day, but longer events can take several days to months. The longer eruptions begin with production of clouds of volcanic ash, sometimes with pyroclastic flows. The amount of magma erupted can be so large that the top of the volcano may collapse, resulting in a caldera. Fine ash can deposit over large areas. Plinian eruptions are often accompanied by loud noises, such as those generated by Krakatoa.

Plinian eruptions, also known as 'Vesuvian eruptions', are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79 and is named after Pliny the Elder who who got killed in that cataclysmic event.

Plinian eruption of Mt Redoubt