Subglacial eruption

A subglacial eruption is a volcanic eruption that has occurred under ice, or under a glacier. Subglacial eruptions can cause dangerous floods, lahars and create hyaloclastite and pillow lava. Only five of these types of eruptions have been recorded in recent history. Subglacial eruptions sometimes form a subglacial volcano called a tuya. Tuyas in Iceland are called table mountains because of their flat tops. Tuya Butte, in northern British Columbia is an example of a tuya. A tuya may be recognized by its stratigraphy which typically consists of a basal layer of pillow basalts overlain by hyaloclastite breccia, tuff, and capped off by a lava flow [Francis, P. Oppenheimer, C: "Volcanoes" page 330-331. Oxford University Press, 2004] . The pillow lavas formed first as a result of subaqueous eruptions in glacial meltwater. Once the vent reaches shallower water eruptions become phreatomagmatic depositing the hyaloclastite breccia. Once the volcanoe emerges through the ice it erupts lava forming the flat capping layer of a tuya. [Moore, J. et, al. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. B12, PAGES 24,577–24,592, 1995 ]

The thermodynamics of subglacial eruptions are very poorly understood. Rare published studies indicate that plenty of heat is contained in the erupted lava, with 1 unit-volume of magma sufficient to melt about 10 units of ice. However, the rapidity by which ice is melted is unexplained, and in real eruptions the rate is at least an order of magnitude faster than existing predictions.

Antarctica eruption

On January, 2008, the British Antarctic Survey (Bas) scientists led by Hugh Corr and David Vaughan, reported (in the journal Nature Geoscience) that 2,200 years ago, a volcano erupted under Antarctica ice sheet (based on airborne survey with radar images). The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier. [ [http://news.bbc.co.uk/2/hi/science/nature/7194579.stm BBC NEWS, Ancient Antarctic eruption noted] ] The ash covered an area the size of new Hampshire and was probably deposited from a 12 km high ash plume. Researchers have detected a mountainous peak some 100 meters beneath the surface believed to be the top of the tuya associated with this eruption. [ [http://environment.newscientist.com/article/dn13205 First subglacial eruption found in Antarctica - earth - 21 January 2008 - New Scientist Environment ] ]

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