My OperaVolcanic plumes
Wednesday, March 15, 2006 4:49:18 PM
When explosive volcanoes erupt they form volcanic plumes (of ashes).
Normally a volcanic plume rises until the atmosphere becomes so thin that the mixture of air and ash loses buoyancy and starts to spread laterally, forming an umbrella. The umbrella spreads and cools for a long time before the ash begins to fall gradually. It resembles the mushroom of an atom bomb blast.
The eruption of the Reventador volcano in Ecuador on 3rd November 2002 was different.
Instead of the usual hot ash, the Reventador eruption appears to have been laden with steam and a fairly cool ash from the destruction of the summit cone. The unusually cool umbrella could not spread for a long time. It rapidly became a heavy mixture of air, steam and ash hovering precariously over the lighter air below. The umbrella on this plume was wavy, like the shell of a scallop.
While most umbrellas produce gradual ash falls, scalloped umbrellas behave differently and might represent a previously unrecognized hazard. The Reventador umbrella probably collapsed rapidly, forming new and especially dangerous ash flows
In a paper in the journal Geophysical Research Letters of 15 March 2006 scientists explain what might have caused the umbrella to scallop.
Reventador is Spanish for "one that explodes". The volcano is an active stratovolcano located in a remote area of the higher Amazon jungle 90 km east of Quito. El Reventador has a history of explosive eruptions, lava flows and lahars. A Lahar is a flow of pyroclastic (volcanic) material mixed with water. A lahar is often produced when a snow-capped volcano erupts and hot pyroclastics melt a large amount of snow or ice. Lahar is by the way an Indonesian word for a mudflow.
Normally a volcanic plume rises until the atmosphere becomes so thin that the mixture of air and ash loses buoyancy and starts to spread laterally, forming an umbrella. The umbrella spreads and cools for a long time before the ash begins to fall gradually. It resembles the mushroom of an atom bomb blast.
The eruption of the Reventador volcano in Ecuador on 3rd November 2002 was different.
Instead of the usual hot ash, the Reventador eruption appears to have been laden with steam and a fairly cool ash from the destruction of the summit cone. The unusually cool umbrella could not spread for a long time. It rapidly became a heavy mixture of air, steam and ash hovering precariously over the lighter air below. The umbrella on this plume was wavy, like the shell of a scallop.
While most umbrellas produce gradual ash falls, scalloped umbrellas behave differently and might represent a previously unrecognized hazard. The Reventador umbrella probably collapsed rapidly, forming new and especially dangerous ash flows
In a paper in the journal Geophysical Research Letters of 15 March 2006 scientists explain what might have caused the umbrella to scallop.
- http://www.physorg.com/news11736.html
- http://www.eurekalert.org/pub_releases/2006-03/uoia-rvp031406.php
Reventador is Spanish for "one that explodes". The volcano is an active stratovolcano located in a remote area of the higher Amazon jungle 90 km east of Quito. El Reventador has a history of explosive eruptions, lava flows and lahars. A Lahar is a flow of pyroclastic (volcanic) material mixed with water. A lahar is often produced when a snow-capped volcano erupts and hot pyroclastics melt a large amount of snow or ice. Lahar is by the way an Indonesian word for a mudflow.
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