http://www.newscientist.com/article/mg20327273.800-climate-change-may-trigger-earthquakes-and-volcanoes.html?full=true
A very interesting issue of New Scientist this week, not just on the
story below, but a section on whether population is the key problem in
terms of the environment.
Please also read the story at the bottom on the possible problems of
'burying the cabron' (CCS etc)
Climate change may trigger earthquakes and volcanoes
* 23 September 2009 by *Richard Fisher*
<http://www.newscientist.com/search?rbauthors=Richard+Fisher>
* Magazine issue 2727 <http://www.newscientist.com/issue/2727>.
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* For similar stories, visit the *Climate Change*
<http://www.newscientist.com/topic/climate-change> Topic Guide
FAR from being the benign figure of mythology, Mother Earth is
short-tempered and volatile. So sensitive in fact, that even slight
changes in weather and climate can rip the planet's crust apart,
unleashing the furious might of volcanic eruptions, earthquakes and
landslides.
That's the conclusion of the researchers who got together last week in
London at the conference on Climate Forcing of Geological and
Geomorphological Hazards. It suggests climate change could tip the
planet's delicate balance and unleash a host of geological disasters.
What's more, even our attempts to stall global warming could trigger a
catastrophic event (see "Bury the carbon")
<http://www.newscientist.com/article/mg20327273.800-climate-change-may-trigger-earthquakes-and-volcanoes.html?full=true#bx272738B1>.
Evidence of a link between climate and the rumblings of the crust has
been around for years
<http://www.newscientist.com/article/mg19025531.300-climate-change-tearing-the-earth-apart.html>,
but only now is it becoming clear just how sensitive rock can be to the
air, ice and water above. "You don't need huge changes to trigger
responses from the crust," says Bill McGuire of University College
London (UCL), who organised the meeting. "The changes can be tiny."
You don't need huge changes to trigger a response from the crust. They
can be tiny
Among the various influences on the Earth's crust, from changes in
weather to fluctuations in ice cover, the oceans are emerging as a
particularly fine controller. Simon Day of the University of Oxford,
McGuire and Serge Guillas, also at UCL, have shown how subtle changes in
sea level may affect the seismicity of the East Pacific Rise, one of the
fastest-spreading plate boundaries.
The researchers focused on the Easter microplate - the tectonic plate
that lies beneath the ocean off the coast of Easter Island - because it
is relatively isolated from other faults. This makes it easier to
distinguish changes in the plate caused by climate systems from those
triggered by regional rumbles. Since 1973, the arrival of El Niño every
few years has correlated with a greater frequency of underwater quakes
between magnitude 4 and 6.
The team is confident that the two are linked. El Niño raises the local
sea level by a few tens of centimetres, and they believe the extra water
weight may increase the pressure of fluids in the pores of the rock
beneath the seabed. This might be enough to counteract the frictional
force that holds the slabs of rock in place, making it easier for faults
to slip. "The changes in sea level are tiny," says Day. "A small
additional perturbation can have a substantial effect."
Small ocean changes can also influence volcanic eruptions, says David
Pyle of the University of Oxford. His study of eruptions over the past
300 years with Ben Mason of the University of Cambridge and colleagues
reveals that volcanism varies with the seasons. The team found that
there are around 20 per cent more eruptions worldwide during the
northern hemisphere's winter than the summer (/Journal of Geophysical
Research/, DOI: 10.1029/2002JB002293
<http://dx.doi.org/10.1029/2002JB002293>). The reason may be that global
sea level drops slightly during the northern hemisphere's winter.
Because there is more land in the northern hemisphere, more water is
locked up as ice and snow on land than during the southern hemisphere's
winter.
The vast majority of the world's most active volcanoes are within a few
tens of kilometres of the coast (see map). This suggests the seasonal
removal of some of the ocean's weight at continental margins as sea
level drops could be triggering eruptions around the world, says Pyle.
The suggestion that some volcanoes erupt when sea levels drop does not
necessarily mean that sea levels rising under climate change will
suppress volcanism. In Alaska, Mount Pavlof erupts more often in the
winter months, and previous research by Steve McNutt of the Alaska
Volcano Observatory puts this down to a local sea level rise of 30
centimetres every winter due to low air pressure and high storm winds.
Pavlof's location means that the extra weight of the adjacent sea could
be squeezing magma towards the surface.
In other regions, additional ocean weight at continental margins as sea
levels rise could bend the crust, reducing compressional conditions,
says McGuire. Magma may then find it easier to reach the surface at
adjacent volcanoes.
All these examples may seem contradictory, but the crucial point is that
any change in sea level may alter regional stresses at continental
margins enough to trigger eruptions in a volcano already primed to
erupt, he says.
Small changes in rainfall can also trigger volcanic eruptions. In 2001,
a major eruption of the Soufrière Hills volcano on the Caribbean island
of Montserrat was set in motion by particularly heavy rainfall. This
destabilised the volcano's dome enough for it to collapse and unleash
magma within. Now it seems even typical tropical rain showers could
trigger an eruption. And climate models suggest that many regions,
including parts of the tropics, are likely to get wetter with climate
change.
Adrian Matthews of the University of East Anglia, UK, and colleagues
measured the minute-by-minute response of Montserrat's volcano after
more than 200 bouts of precipitation over three years. The team found
that these events, which Matthews says were typical of tropical weather,
were followed by two days of increased volcanic activity.
A rainy day increased the likelihood of dome collapse from 1.5 per cent
to 16 per cent. "It wouldn't have to be spectacularly heavy rainfall,"
says Matthews. "You don't have to have a hurricane." (/Journal of
Volcanology and Geothermal Research/, DOI:
10.1016/j.jvolgeores.2009.05.010
<http://dx.doi.org/10.1016/j.jvolgeores.2009.05.010>)
Perhaps the greatest geological hazards during climate change will be
the result of melting ice sheets. Apart from the risk that loose
sediments exposed by melted ice could slip into the sea as
tsunami-generating landslides, the removal of heavy ice could also
trigger volcanic eruptions. "Even thinning of a few tens of metres could
make a difference," says Andrew Russell of the University of Newcastle
in the UK.
For example, Iceland's Vatnajökull ice cap sits over a plate boundary
and several volcanoes. That ice is likely to disappear within the next
two centuries. "If that happens you'll get rid of an awful lot of weight
that will allow an increase in volcanic activity," says Russell. In the
wake of the last ice age, volcanism was up to 30 times greater in
northern Iceland compared with today (/Earth Surface Processes and
Landforms/, DOI: 10.1002/esp.1811 <http://dx.doi.org/10.1002/esp.1811>).
Icy eruptions could reverberate round the world. In 1783, the Icelandic
volcano Laki sent a sulphurous smog over Europe, plunging it into an
extreme winter that killed thousands.
For now, it is unclear just how much climate change will affect the
frequency and intensity of quakes and eruptions, says McGuire, because
Earth's sensitivity to climate is only now emerging. There is not yet
enough data to build predictive climate models linking the two systems.
But it's crucial that we consider just how easily our actions could
provoke the planet, he argues. "It's serious science, not scaremongering."
Bury the carbon and set off a quake
It all looked so promising - tidy carbon dioxide away underground and
forget about it. But even as the US's first large-scale sequestration
operation is getting off the ground at the Mountaineer plant in West
Virginia
<http://sequestration.mit.edu/tools/projects/aep_alstom_mountaineer.html>,
geophysicists are concerned that burying the carbon could trigger
earthquakes and tsunamis.
In a carbon sequestration power plant (CCS), CO_2 is extracted from the
exhaust then pumped into aquifers and old gas fields several kilometres
beneath the Earth's surface. So far so good. But the CO_2 expands as it
rises through the porous rock, increasing pressure inside. "If enough
CO_2 is injected into an aquifer, it could increase the pressure enough
to reactivate a fault and trigger an earthquake," warns Andrew Chadwick
of the British Geological Survey.
Chemical reactions between the injected CO_2 , water and rock could also
destabilise the rock, says Ernest Majer, a seismologist at the Lawrence
Berkeley National Laboratory in California who briefed the Senate on CCS
hazards this week. "It's such a new technology that none of these issues
have been addressed," says Majer. Even storage sites far from human
settlements could have disastrous effects, warns Christian Klose, a
geophysicist at the Think Geohazards consulting firm in California. A
CCS facility at the Sleipner gas field in the North Sea, may have
triggered a magnitude 4 earthquake in 2008. Had it been bigger, says
Klose, it might have triggered a tsunami.
*Shanta Barley*
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