Friday, January 3, 2014

AVO Upgrades Cleveland Alert To Orange

Alaska's notorious Cleveland Volcano has been upgraded from yellow alert status to orange amid recent explosions from the summit crater. The volcano has been in a state of unrest for several years and has had periods of summit crater dome growth, followed by explosions that destroy the dome, only to restart the process. Typically (during this particular unrest period), Cleveland will have a brief explosion that 'unplugs' the summit, ejecting hot ash and blocky lava, and then change to a period of very slow effusion that builds a plug or dome within the crater. After the dome reaches nearly the rim of the crater, this is when the explosions have been occurring usually.

Alaska Volcano Observatory (AVO) does not have monitoring equipment on Cleveland due to its remote location within the Aleutian Islands chain of volcanoes. They rely on satellite data for the majority of their reports, mainly from MODIS or German satellites. Some seismic signals are strong enough to be detected by other 'nearby' monitoring stations, but it is quite probable that Cleveland volcano is a bit more active than we give it credit for, having had probable explosions that have gone undocumented, or unnoticed.

Currently in Alaska, there are only two volcanoes showing activity of any kind. Veniaminof volcano has gone up and down from Yellow to orange and back to yellow several times in the past year or so, with periodic lava effusion from the summit cone.

In a typical year, at least one or two volcanoes is usually in a state of unrest or eruption, and Cleveland volcano is one of the most frequently active in the chain.

Cleveland volcano does not pose any threat to human populations, but does lay under many air travel routes, so an Orange designation means that air traffic may need to divert to other routes in order to avoid being unexpectedly caught in an ash column, as happened with the 1989 eruption of Redoubt volcano (which also had an eruption in 2009). An airline full of passengers was temporarily disabled as it flew through a column of ash some 45,000 meters in height, causing its engines to choke on volcanic ash that turned to glass within the turbine. Fortunately the plane was able to restart its engines before it would have crashed, and landed safely.

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