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Author Topic: What causes a dormant volcano to be 'awake' again?  (Read 4216 times)

Offline The Scientist

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Please answer as detailed as possible. Thank you!


 

Offline The Scientist

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What causes Dormant volcanoes to sleep?
« Reply #1 on: 13/07/2010 10:00:25 »
Dormant volcanoes literally means 'sleeping volcano' but what is it which causes it to be 'asleep'?

Please elaborate upon explanation. Thanks.
 

Offline SeanB

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What causes Dormant volcanoes to sleep?
« Reply #2 on: 13/07/2010 18:24:47 »
More like not having erupted since recorded history began is a good reason, very few volcanoes are truly dormant, only that the last eruption was so long ago that there is no written or oral memory passed down about it. Any volcano can erupt again, as it is an indication of a weak spot in the crust of the earth, and only requires that it either has enough magma build up under it or a so called hot spot forms under it. Yellowstone in the USA is a good example, it has not erupted in recorded history, although other volcanoes around it have.
 

Offline Stefanb

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What causes a dormant volcano to be 'awake' again?
« Reply #3 on: 15/07/2010 05:13:05 »
Volcanoes can be created two ways:
Convergent/Divergent Plate Boundaries;
and Geothermal Hot Spots.
When a continental plate (characerized by a thicker, more dense layer) and an oceanic plate (thin and more malleable) converge, the oceanic plate slips underneath the continental plate and melts as it dips into the mantle underneath the continental plate. The excess magma formed from the melted oceanic plate floats up and slowly melts through the continental plate. The largest example of this is the "Ring of Fire". When two plates diverge (such as in the Mid-Atlantic Ridge), magma from the mantle comes up through the resulting fissure and builds up into volcanoes over time. Iceland is the largest example above sea level.
Geothermal Hot Spots are points where the mantle is thinner than usual, allowing for a more direct transfer of energy from the Earth's inner core to the crust. This melts areas of the crust, and creates volcanoes. The most commonly known "Hot Spot Volcanoes" are the Hawaiian Islands.

Dormancy is only permanent in Hot Spot Volcanoes, because as the crust shifts over the mantle, the hot spot affects a new area. Dormancy in volcanoes resulting from convergent/divergent plate boundaries is temporary, and is the period during which pressure and heat build up underground before an eruption.
« Last Edit: 15/07/2010 17:27:26 by Stefanb »
 

Offline Bass

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What causes a dormant volcano to be 'awake' again?
« Reply #4 on: 15/07/2010 17:21:51 »
Volcanoes can be created two ways:
Convergent/Divergent Plate Boundaries;
and Geothermal Hot Spots.

Geothermal Hot Spots are points where the mantle is thinner than usual, allowing for a more direct transfer of energy from the Earth's inner core to the crust. This melts areas of the crust, and creates volcanoes. Two commonly known "Hot Spot Volcanoes" are the Hawaiian Islands and Mnt. St. Helens in Washington.


Just a minor correction:
Mt St. Helens is not a hot spot- rather it is one of many Cascade volcanoes along a convergent boundary.
Hot spots are not caused by thinned mantle.  They may be caused by deep mantle plumes or they may originate in the upper mantle- jury is still out on this.
 

Offline Stefanb

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What causes a dormant volcano to be 'awake' again?
« Reply #5 on: 15/07/2010 17:26:32 »
Ah, thank you for the correction  :)
The late hours do not do well for my thought proccess
 

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What causes a dormant volcano to be 'awake' again?
« Reply #5 on: 15/07/2010 17:26:32 »

 

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