Monday, April 29, 2013

Re: [Geology2] Maars and Phreatic Eruptions




You're very welcome, Vic. The purpose of this group is to learn, and not all of us here have degrees in geology. :-) I'm thinking of putting geology.com's articles on volcanoes in a pdf of its own and then uploading it here. I think it would make a useful guide. I'll do that once I have the time. At the moment, I'm dealing with kittens. lol Yes, kittens. Long story, but this situation could only happen to me. Oy.

Lin


On Mon, Apr 29, 2013 at 5:09 AM, Victor Healey <vic.healey@gmail.com> wrote:
 

Thank you for taking the time to make this post Lin. This was one of the most interesting explainations that was simple enough that even I understood the terminology used.


Victor




Sent from Incredimail for iPad

From: Lin Kerns
Sent: Friday
To: Geology2
Subject: [Geology2] Maars and Phreatic Eruptions

 

Maars and Phreatic Eruptions


A maar is a volcanic crater that forms when magma contacts ground water to produce a steam explosion.


Views of East Ukinrek Maar Crater, that formed in April, 1977 during a 10-day eruption. This eruption provided a rare - and the most recent - opportunity for researchers to observe the formation of a maar by volcanic activity. (A) A vertical view of the crater which is about 300 meters across. Not visible is a 49 meter-high lava dome within the crater that is now covered by water. The ground surrounding the crater is covered with tephra in this July 1990 photo by the Fish and Wildlife Service. Enlarge. (B) A photograph of the phreatomagmatic eruption and plume taken during the April, 1977 eruption. Image by the United States Geological Survey. Enlarge. (C) A view of the southeast crater wall showing stratified tephra deposits produced during the 1977 eruption. About 15 meters of tephra overlies a thin layer of glacial till that caps ash-flow deposits produced by an earlier eruption at Ugashik Caldera. Image by the United States Geological Survey. Enlarge. [1]





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