Volcanic form
A
subglacial volcano
, also known as a
glaciovolcano
, is a volcanic form produced by
subglacial eruptions
or eruptions beneath the surface of a
glacier
or
ice sheet
which is then melted into a
lake
by the rising
lava
. Today they are most common in
Iceland
and
Antarctica
; older formations of this type are found also in
British Columbia
and
Yukon 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 in
pillow lava
shapes similar to those of
underwater volcanoes
. When the pillow lavas break off and roll down the volcano slopes, pillow
breccia
,
tuff
breccia, and
hyaloclastite
form. The meltwater may be released from below the ice as happened in
Iceland
in 1996 when the
Grimsvotn
caldera erupted, melting 3 km
3
of ice and giving rise to a large
glacial 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 erupted
subaerially
, 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 called
tuyas
, named after
Tuya Butte
in northern British Columbia by Canadian geologist
Bill Mathews
in 1947. In Iceland, such volcanoes are also known as
table mountains
.
Jokulhlaups
[
edit
]
Subglacial eruptions often cause
jokulhlaups
or great floods of water. In November 1996 the
Grimsvotn
Volcano beneath the Vatnajokull ice sheet erupted and caused a Jokulhlaup that affected more than 750 km
2
(290 sq mi) and destroyed or severely damaged several bridges.
[2]
Sonia Esperanca, program director in the
National 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]
Antarctica eruption
[
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]
In 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
.
[4]
On Mars
[
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]
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]
Ice cores
[
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]
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 SO
2?
4
.
[6]
See also
[
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]
References
[
edit
]
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Types
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Anatomy
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Processes
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Measurements
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Volcanic relations
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Landforms
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