Tuesday, 15 November 2016

Earthquakes and climate change

Isostatic rebound and our rocky future

Kevin Hester

31 July, 2016

One example of where relatively small changes to geological stress can have a big impact on volcanic activity is the Pavlov volcano in Alaska. As McGuire describes, this volcano only erupts during Autumn and Winter. At that time storms ride up into a nearby ocean zone, pushing an average 10cm or 15cm rise in sea level. The added weight of the water is enough to torque the crust and push magma out. Now imagine the kind of extra volcanic activity that could result from 1, 6, or 250 feet of global sea level rise under the raging rate of human-caused warming and you begin to understand the concern.”We have let the Genie out of the bottle, It will never be the same again. 6C will melt most if not the entire ice caps. imagine how much ‘Torgue’ that will put on the plates?

Between about 20,000 and 5,000 years ago, our planet underwent an astonishing climatic transformation. Over the course of this period, it flipped from the frigid wasteland of deepest and darkest ice age to the – broadly speaking – balmy, temperate world upon which our civilisation has developed and thrived. During this extraordinarily dynamic episode, as the immense ice sheets melted and colossal volumes of water were decanted back into the oceans, the pressures acting on the solid Earth also underwent massive change. In response, the crust bounced and bent, rocking our planet with a resurgence in volcanic activity, a proliferation of seismic shocks and burgeoning giant landslides.

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.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.”

Our planet is always on the move, but sometimes it is more restless than usual. As the last ice age came to an end, around 10,000 years ago, there was a surge in volcanic activity as ice caps melted, decreasing pressure on the Earth’s crust.
Since then our planet has reached a steady state, with around 50 volcanoes erupting each year and around 150 earthquakes greater than magnitude six. But geo-hazards expert Bill McGuire is concerned that human-induced climate change may bring a resurgence in activity in the coming centuries. “In areas of major ice loss, such as Alaska, Iceland, the Andes and Himalayas we may see a rise in earthquakes, volcanism and landslides” says McGuire, who describes this scenario in Waking the Giant. “It only takes the pressure of a handshake to trigger a quake or volcanic blast in a primed system.”

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