More Fatal Earthquakes to Come, Geologists Warn

http://www.newsweek.com/nepal-earthquake-could-have-been-manmade-disaster-climate-change-brings-326017.html?piano_d=1

By Alex Renton / April 28, 2015

The untold – and terrifying – story behind the earthquake that devastated Nepal last Saturday morning begins with something that sounds quite benign. It’s the ebb and flow of rainwater in the great river deltas of India and Bangladesh, and the pressure that puts on the grinding plates that make up the surface of the planet.

Recently discovered, that causal factor is seen by a growing body of scientists as further proof that climate change can affect the underlying structure of the Earth.

Because of this understanding, a series of life-threatening “extreme geological events” – earthquakes, volcanoes and tsunamis – is predicted by a group of eminent geologists and geophysicists including University College London’s Bill McGuire, professor emeritus of Geophysical and Climate Hazards.

“Climate change may play a critical role in triggering certain faults in certain places where they could kill a hell of a lot of people,” says Professor McGuire. Some of his colleagues suspect the process may already have started.

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Evidence from the end of the last Ice Age has already shown that the planet’s uneasy web of seismic faults – cracks in the crust like the one that runs along the Himalayas – are very sensitive to the small pressure changes brought by change in the climate. And a sensitive volcano or seismic faultline is a very dangerous one.

The disappearing ice, sea-level rise and floods already forecast for the 21st century are inevitable as the earth warms and weather patterns change – and they will shift the weight on the planet. Professor McGuire calls this process “waking the giant” – something that can be done with just a few gigatonnes of water in the right – or wrong – place.

“These stress or strain variations – just the pressure of a handshake in geological terms – are perfectly capable of triggering a quake if that fault is ready to go,” he tells Newsweek.

Any schoolchild geographer knows the underlying cause of earthquakes like that in Nepal: it is the uneasy grinding of the continent-sized plates that float over the Earth’s molten core. This process that went into overdrive when the ice sheets started withdrawing 20,000 years ago, destablising the “mantle”. The latest event in that endless process came just before midday local time on the 25 April, when the section that holds up India slipped under the Eurasian plate.

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Dr Pierre Bettinelli was the scientist who in 2007 first showed how this vast flush of rainwater, second only to that of the Amazon basin, affects earthquakes in the Himalayas. He spoke to Newsweek from a base in the Algerian desert where he is researching the effects of oil-well drilling – another man-made cause of earthquake.

“Imagine a piece of wood on water – that’s the Indian plate – push down on it with your foot and you create compression, disturbance, in the water beside it. That you see in the increased number of seismic events at the edge of the plate.”

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Meanwhile, of course, climate change has been shown to be causing enormous and disturbing changes in the size and shape of the South Asian monsoon, while human tampering has played a part in floods.

UCL’s Professor Bill McGuire has few doubts that recently discovered effects like this warn of catastrophe. In a recent book, Waking the Giant: How a Changing Climate Triggers Earthquakes, Tsunamis and Volcanoes, he ponders the effects of the 100m rise of sea-levels that’s threatened should all the remaining ice on the planet melt.

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“Across the world,” McGuire writes, “as sea levels climb remorselessly, the load-related bending of the crust around the margins of the ocean basins might – in time – act to sufficiently ‘unclamp’ coastal faults such as California’s San Andreas, allowing them to move more easily; at the same time acting to squeeze magma out of susceptible volcanoes that are primed and ready to blow.”

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But already McGuire and colleagues have seen the effects of quite small sea-level rise on one of Alaska’s faults.

“There’s a volcano in Alaska, Pavlov, that only erupts during the autumn and winter. The 10cm or 15cm rise in sea level during the winter months, when low pressure comes over, is enough to bend the crust and squeeze magma out. That’s an example of how tiny a change you need,” he said.

Meanwhile, geologists modelling the effect of retreating ice sheets in the northern hemisphere predict more volcanic activity as pressure is released on fault lines. McGuire points to three eruptions in five years in Iceland – “You can’t say that’s statistical proof but … it makes you think.”

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“Ice unloading at the end of the ice ages produced a flurry of volcanic eruptions. That makes sense to me – it’s very true that if you take pressure off a magmatic system that can activate eruptions. There’s solid evidence of that in Iceland.”

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