Subglacial eruption: 1 water vapor cloud, 2 lake, 3 ice, 4 layers of lava and ash, 5 strata, 6 pillow lava, 7 magma conduit, 8 magma chamber, 9 dike
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. 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.[1] 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 volcano emerges through the ice, it erupts lava, forming the flat capping layer of a tuya.[2]
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.
[edit] 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 the 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.[3] The ash covered an area the size of New Hampshire (23,000 square kilometres) 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.[4]
[edit] List of volcanoes with Holocene subglacial eruptions
[edit] Iceland
[edit] South America
[edit] References
- ^ Francis, P. Oppenheimer, C: "Volcanoes" page 330-331. Oxford University Press, 2004
- ^ Moore, J. et, al. JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 100, NO. B12, PAGES 24,577–24,592, 1995
- ^ Black, Richard (20 January 2008). "Ancient Antarctic eruption noted". BBC News (London: BBC). http://news.bbc.co.uk/2/hi/science/nature/7194579.stm. Retrieved 22 October 2011.
- ^ First subglacial eruption found in Antarctica - earth - 21 January 2008 - New Scientist Environment
