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Web address:
http://www.sciencedaily.com/releases/2012/10/
121012074747.htm
Scientists Identify Trigger for Explosive Volcanic Eruptions
enlarge
Southampton students conducting fieldwork on the Las Cañadas volcanic caldera.
(Credit: Barry Marsh)
ScienceDaily (Oct. 12, 2012) Scientists from the University of Southampton
have identified a repeating trigger for the largest explosive volcanic
eruptions on Earth.
The Las Cañadas volcanic caldera on Tenerife, in the Canary Islands, has
generated at least eight major eruptions during the last 700,000 years. These
catastrophic events have resulted in eruption columns of over 25km high and
expelled widespread pyroclastic material over 130km. By comparison, even the
smallest of these eruptions expelled over 25 times more material than the 2010
eruption of Eyjafjallajökull, Iceland.
By analysing crystal cumulate nodules (igneous rocks formed by the accumulation
of crystals in magma) discovered in pyroclastic deposits of major eruptions,
the scientists found that pre-eruptive mixing within the magma chamber -- where
older cooler magma mixed with younger hotter magma -- appears to be the
repeating trigger in large-scale eruptions.
These nodules trapped and preserved the final magma beneath the volcano
immediately before eruption. Dr Rex Taylor, Senior Lecturer in Ocean and Earth
Science at the University of Southampton, investigated nodules and their
trapped magma to see what caused the eruptions. He found that the nodules
provide a record of the changes occurring in the magma plumbing right through
to the moment the volcano erupted.
Dr Taylor says: "These nodules are special because they were ripped from the
magma chamber before becoming completely solid -- they were mushy, like balls
of coarse wet sand. Rims of crystals in the nodules grew from a very different
magma, indicating a major mixing event occurred immediately before eruption.
Stirring young hot magma into older, cooler magma appears to be a common event
before these explosive eruptions."
Co-author of the study, Dr Tom Gernon, Lecturer in Ocean and Earth Science at
the University of Southampton, says: "The analysis of crystal nodules from the
volcano documents the final processes and changes immediately prior to eruption
-- those triggering the catastrophic eruptions. The very presence of mushy
nodules in the pyroclastic deposits suggests that the magma chamber empties
itself during the eruption, and the chamber then collapses in on itself forming
the caldera."
The Las Cañadas volcano is an IAVCEI (International Association of Volcanology
and Chemistry of the Earth's Interior) Decade Volcano -- identified by the
international community as being worthy of particular study in light of their
history of large, destructive eruptions and proximity to populated area.
Dr Gernon, who is based at the National Oceanography Centre at Southampton's
waterfront campus with Dr Taylor, adds: "Our findings will prove invaluable in
future hazard and risk assessment on Tenerife and elsewhere. The scale of the
eruptions we describe has the potential to cause devastation on the heavily
populated island of Tenerife and major economic repercussions for the wider
European community."
The paper is published in the latest issue of the open access journal
Scientific Reports.
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Story Source:
The above story is reprinted from materials provided by University of
Southampton.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
Michael J. Stock, Rex N. Taylor, Thomas M. Gernon. Triggering of major
eruptions recorded by actively forming cumulates. Scientific Reports, 2012; 2
DOI: 10.1038/srep00731
Need to cite this story in your essay, paper, or report? Use one of the
following formats:
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University of Southampton (2012, October 12). Scientists identify trigger for
explosive volcanic eruptions. ScienceDaily. Retrieved October 13, 2012, from
http://www.sciencedaily.com /releases/2012/10/121012074747.htm
Note: If no author is given, the source is cited instead.
Disclaimer: Views expressed in this article do not necessarily reflect those of
ScienceDaily or its staff.
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