Asubglacial volcano, also known as aglaciovolcano, is a volcanic form produced bysubglacial eruptions or eruptions beneath the surface of aglacier orice sheet which is then melted into alake by the risinglava. Today they are most common inIceland andAntarctica; older formations of this type are found also inBritish Columbia andYukon Territory,Canada.
During the eruption, the heat of the lava from the subglacial volcano melts the overlying ice. The water quickly cools the lava, resulting inpillow lava shapes similar to those ofunderwater volcanoes. When the pillow lavas break off and roll down the volcano slopes, pillowbreccia,tuff breccia, andhyaloclastite form. The meltwater may be released from below the ice as happened inIceland in 1996 when theGrímsvötn caldera erupted, melting 3 km3 of ice and giving rise to a largeglacial lake outburst flood.
The shape of subglacial volcanoes tends to be quite characteristic and unusual, with a flattened top and steep sides supported against collapse by the pressure of the surrounding ice and meltwater. If the volcano eventually melts completely through the ice layer, then horizontal lava flows are deposited, and the top of the volcano assumes a nearly level form. However, if significant amounts of lava are later eruptedsubaerially, then the volcano may assume a more conventional shape. In Canada the volcanos have been known to form both conical and nearly level shapes.[1] The more distinctly flat-topped, steep-sided subglacial volcanoes are calledtuyas, named afterTuya Butte in northern British Columbia by Canadian geologistBill Mathews in 1947. In Iceland, such volcanoes are also known astable mountains.
Subglacial eruptions often causejökulhlaups or great floods of water. In November 1996 theGrímsvötn Volcano beneath the Vatnajökull ice sheet erupted and caused a jökulhlaup that affected more than 750 km2 (290 sq mi) and destroyed or severely damaged several bridges.[2] Sonia Esperanca, program director in theNational Science Foundation, commented on the danger of subglacial volcanoes: "When an ice-covered volcano erupts, the interplay among molten magma, ice and meltwater can have catastrophic results."[3]
In 2008,British Antarctic Survey scientists led by Hugh Corr and David Vaughan, reported (in the journalNature Geoscience) that 2,200 years ago, avolcano erupted under theAntarctica ice sheet (based onairborne survey with radar images). The biggest eruption in Antarctica in the last 10,000 years, the volcanic ash was found deposited on the ice surface under theHudson Mountains, close toPine Island Glacier.[4]
Many scientists believe that liquid water exists many kilometers below the surface of Mars, but at this point in time it is impossible to drill to those depths with the rovers in existence. Meredith Payne and Jack Farmer of Arizona State University have studied images from the Viking and Mars Orbiter cameras in search of possible sub-glacial volcanoes that could carry microbes to the surface.[5]
It is possible to track catastrophic subglacial volcano eruptions in time with the analysis of ice cores such as the Vostok core. Subglacial volcanic eruptions are identified by layers of high concentrations of NO−
3 and SO2−
4.[6]
Media related toSubglacial volcanoes at Wikimedia Commons| Types |  | |
|---|---|---|
| Volcanic rocks | ||
| Lists and groups | ||
