Sea levels influence eruptions on volcanic island
The rise and fall of sea levels influence the likelihood of volcanic
eruptions on the Greek island of Santorini

Date:
August 2, 2021
Source:
Oxford Brookes University
Summary:
The rise and fall of sea levels influence the likelihood of
volcanic eruptions on the Greek island of Santorini, new research
has discovered.

Analyzing the timings of eruptions over hundreds of thousands of
years, the researchers found that a 40 meter fall in sea level is a
crucial point beyond which eruptions are more likely to occur. The
findings could have implications for millions of people living on
volcanic islands around the world.



FULL STORY ==========================================================================
The rise and fall of sea levels influence the likelihood of volcanic
eruptions on the Greek island of Santorini, new research led by Oxford
Brookes University has discovered. Analysing the timings of eruptions
over hundreds of thousands of years, the researchers found that a 40
metre fall in sea level is a crucial point beyond which eruptions are
more likely to occur. The findings could have implications for millions
of people living on volcanic islands around the world.


========================================================================== Santorini -- cliffs reveal history of eruptions The research on the
popular tourist destination was led by Dr Christopher Satow, Senior
Lecturer in Physical Geography at Oxford Brookes.

He says there are clues about past volcanic activity on Santorini in the
layers of rock on the cliff face encircling the inner part of the island:
"A huge eruption 3,600 years ago caused the centre of what was then
a conical island to sink into the sea, revealing an extraordinarily
detailed history of over 200 volcanic eruptions preserved within the
remaining circle of cliffs.

"Comparing this eruption history to a sea level record allowed us to
show for the first time that the sea level has had an important role in determining the timing of eruptions at Santorini, and probably at many
other island volcanoes around the world.

"The mechanism is quite simple: falling sea levels remove mass from the
Earth's crust and the crust fractures as a result. These fractures allow
magma to rise and feed eruptions at the surface." The researchers say
that eruptions at hundreds of other volcanic islands around the world may
also have been influenced by fluctuations in sea level. Dr Satow added:
"Just as when you pull a plug out of the bath, the water level drops
everywhere throughout the bath at the same time; in a similar way,
sea level changes occur at the same time everywhere across the globe."


========================================================================== Volcanic eruptions and climate change Volcanic eruptions can change the climate, for example the eruption of the Philippines' Mt. Pinatubo in
1992 resulted in a fall in global temperature of 0.5oC.

But Dr Satow says the climate also impacts on volcanic activity: "What
is less well known is that on long timescales, the climate can also
affect volcanoes.

As ice sheets retreated across volcanic landscapes after the last ice age,
the removal of mass changed the stress conditions in the Earth's crust, allowing the fractures which feed volcanic eruptions to form more easily.

"As these ice sheets melted the global sea level rose rapidly, by around
100 meters, adding a significant mass to the crust around many volcanic
islands which, in theory, should alter their eruptive activity." Dr Satow concludes: "57% of the world's volcanoes are islands or are coastal, and
are often home to large populations. Further vital research is needed to
fully understand the effects of changing sea level on these volcanoes and
the risks they pose to their populations." Dr Satow collaborated with researchers from Royal Holloway University of London, Keele University,
the University of Oxford, Uppsala University in Sweden, the University
of Portsmouth and the University of Leicester.

========================================================================== Story Source: Materials provided by Oxford_Brookes_University. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Chris Satow, Agust Gudmundsson, Ralf Gertisser, Christopher
Bronk Ramsey,
Mohsen Bazargan, David M. Pyle, Sabine Wulf, Andrew J. Miles, Mark
Hardiman. Eruptive activity of the Santorini Volcano controlled
by sea- level rise and fall. Nature Geoscience, 2021; DOI:
10.1038/s41561-021- 00783-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210802115019.htm

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