Monday, May 5, 2014

Mt St Helens Is Inflating Again

It appears that Mt St Helens is experiencing gradual re-inflation of its magma chamber, leading some to feel concern that the volcano will erupt again in the near future. St Helens last eruptive period ended in 2008 with a dome building event, which consisted of slow extrusion of a central lava dome, and occasional ash fall due to collapse of the dome. The current inflation period does not indicate an eruption is imminent, although it does significantly raise that possibility.

It is common for volcanoes to immediately begin 'recharging' after the end of eruptive activity. Other volcanoes that display this behavior are volcanoes such as Hawaii's Mauna Loa, or Kilauea, which experience frequent eruptions and deflation/inflation (DI) events. Mauna Loa began to inflate immediately after its 1983-84 eruption, stopped in 2009, and gradually resumed inflating in 2010. There are no current indications despite this inflation that an eruption of Mauna Loa is imminent, however it is a cause for vigilance.

St Helens erupted in May 1980 after bulging was detected on its north flank, followed by a massive collapse and associated eruption. It is one of the largest eruptions in recent US history, and is frequently used as a comparison benchmark for other volcanic eruptions. Monitoring of Cascade range volcanoes, and other US volcanoes was stepped up after the 1980 eruption, as the US finally realized the threat that monitored volcanoes can present. St Helens was monitored prior to its eruption, and warnings were issued that the volcano might erupt, but sadly some 57 people were killed and up to 250 homes were destroyed in the famous eruption.

USGS heavily monitors St Helens, as it is one of only several volcanoes on the West Coast with a recent history of eruption. In 1914-1917, California's Mt Lassen erupted, and Washington's Mount Rainier erupted in 1894.

Currently, all volcanoes on the West Coast of the US are 'green' meaning there are no warnings in place at the moment.

St Helens, Rainier, Shasta, and several other Cascade range volcanoes are considered a high risk for populations should they erupt. Rainier in particular is of major concern to scientists who warn that even without an eruption, it is at severe risk of collapse and associated hot mudslides known as 'lahars', which can cause major damage down well established canyons and drainage channels. There is an alert system in place, however it does not provide a lot of time to react should it go off.


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