Global warming causes earthquakes and volcanic eruptions (yes, this story is real)

This story has sparked much laughter among global warming skeptics.  The history of exaggerated claims  by warmists have made the skeptics sloppy.  This claim has a basis in real research. 

  1. Ice cap thaw may awaken Icelandic volcanoes“, Reuters, 16 April 2010
  2. Will present day glacier retreat increase volcanic activity?“, Carolina Pagli and Freysteinn Sigmundsson, Geophysical Research Letters, 7 May 2008 — “Stress induced by recent glacier retreat and its effect on magmatism at the Vatnajokull ice cap, Iceland”
  3. Melting ice caps may trigger more volcanic eruptions“, New Scientist, 3 April 2008 — Article about the above study.
  4. Retreating Glaciers Spur Alaskan Earthquakes“, NASA, 2 August 2004

Excerpts 

(1)  “Ice cap thaw may awaken Icelandic volcanoes“, Reuters, 16 April 2010 — Excerpt: 

A thaw of Iceland’s ice caps in coming decades caused by climate change may trigger more volcanic eruptions by removing a vast weight and freeing magma from deep below ground, scientists said on Friday. They said there was no sign that the current eruption from below the Eyjafjallajokull glacier that has paralysed flights over northern Europe was linked to global warming. The glacier is too small and light to affect local geology. 

“Our work suggests that eventually there will be either somewhat larger eruptions or more frequent eruptions in Iceland in coming decades,” said Freysteinn Sigmundsson, a vulcanologist at the University of Iceland. Global warming melts ice and this can influence magmatic systems,” he told Reuters. The end of the Ice Age 10,000 years ago coincided with a surge in volcanic activity in Iceland, apparently because huge ice caps thinned and the land rose. “We believe the reduction of ice has not been important in triggering this latest eruption,” he said of Eyjafjallajokull. “The eruption is happening under a relatively small ice cap.” 

(2)  “Will present day glacier retreat increase volcaninc activity?“, Carolina Pagli and Freysteinn Sigmundsson, Geophysical Research Letters, 7 May 2008 — Abstract: 

 

Global warming causes retreat of ice caps and ice sheets. Can melting glaciers trigger increased volcanic activity? Since 1890 the largest ice cap of Iceland, Vatnajökull, with an area of ∼8000 km2, has been continuously retreating losing about 10% of its mass during last century. Present-day uplift around the ice cap is as high as 25 mm/yr. We evaluate interactions between ongoing glacio-isostasy and current changes to mantle melting and crustal stresses at volcanoes underneath Vatnajökull. The modeling indicates that a substantial volume of new magma, ∼0.014 km3/yr, is produced under Vatnajökull in response to current ice thinning. Ice retreat also induces significant stress changes in the elastic crust that may contribute to high seismicity, unusual focal mechanisms, and unusual magma movements in NW-Vatnajökull. 

(3)  “Melting ice caps may trigger more volcanic eruptions“, New Scientist, 3 April 2008 — Article about the above study.  Excerpt: 

Carolina Pagli of the University of Leeds, UK, and Freysteinn Sigmundsson of the University of Iceland have calculated the effects of the melting on the crust and magma underneath. They say that, as the ice disappears, it relieves the pressure exerted on the rocks deep under the ice sheet, increasing the rate at which it melts into magma. An average of 1.4 cubic kilometres has been produced every century since 1890, a 10% increase on the background rate. 

… The situation in Iceland does not necessarily mean magma will be melting faster around the world. Vatnajökull sits atop a boundary between plates in the Earth’s crust, and it is this configuration that is allowing the release in pressure to have such a great effect deep in the mantle. But the thinning ice has another effect on volcanoes which will be more widespread. 

As the amount of weight on the crust changes, geological stresses inside the crust will also change, increasing the likelihood of eruptions. “Under the ice’s weight, the crust bends and as you melt the ice the crust will bounce up again,” explains Bill McGuire of University College London in the UK, who was not involved in the study. 

The shifting stress might even cause eruptions in unexpected places. “We think that during the Gjàlp eruption, magma reached the surface at an unusual location, mid-way between two volcanoes, because of these stress changes,” says Pagli. 

(4)  “Retreating Glaciers Spur Alaskan Earthquakes“, NASA, 2 August 2004: 

Could an extra warm summer cause an earthquake in your backyard? Probably not… unless you live in Alaska. You probably know that friction in the earth’s crust causes earthquakes, but did you know that a little extra sunshine might increase your chances of experiencing an earthquake if you live where glaciers are present? That’s because as glaciers melt, they retreat and lighten the load on massive rocky slabs of Earth’s crust called tectonic plates. This frees the plates up to move against each other and cause the friction needed to make earthquakes. 

Scientists at NASA and United States Geological Survey (USGS) are using NASA satellite and global positioning system receivers, as well as computer models, to study movements of Earth’s plates and shrinking glaciers in southern Alaska. Glaciers here are very sensitive to climate change. Higher temperatures and changes in precipitation over the last 100 years appear to be contributing to an increase in glacier melting in the area. 

Southern Alaska is also prone to earthquakes because a tectonic plate under the Pacific Ocean is pushing into the coast, building up lots of pressure. The weight of a big glacier on top of these earthquake active areas can help keep things stable. But, as the glaciers melt and their load on the plate lessens, there is a greater likelihood of an earthquake happening to relieve the large strain underneath. Even though shrinking glaciers make it easier for earthquakes to occur, the forcing together of tectonic plates is the main reason behind major earthquakes. 

Scientists believe that a 1979 earthquake in southern Alaska, called the St. Elias earthquake, was promoted by rapidly melting glaciers in the area. The earthquake had a magnitude of 7.2 on the Richter Scale. Pressure from colliding tectonic plates had been building since 1899 when the last big earthquake had occurred in this area. Between 1899 and 1979, many glaciers in this region thinned by hundreds of meters and some completely disappeared. 

To study the link between melting glaciers and the St. Elias earthquake, scientists used aerial and ground photography along with satellite and ground measurements to estimate how much ice was lost. Then they calculated how much instability the loss may have caused in the Earth’s crust. They found the loss of ice would have been enough to encourage the 1979 St. Elias earthquake. 

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