Are Global Warming, Volcanoes and Earthquakes Linked?
London, UK - 25th April 2010, 21:35 GMT
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A thaw of ice caps caused by global warming may trigger more volcanic eruptions in coming decades by removing a vast weight and freeing magma from deep below ground, research suggests. Eventually there will be either somewhat larger eruptions or more frequent eruptions in coming decades. 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. Climate chaos could also trigger volcanic eruptions or earthquakes in places such as Mount Erebus in Antarctica, the Aleutian islands of Alaska or Patagonia in South America.
Vatnajökull Glacier Ice Cap, Iceland
Scientists at NASA and United States Geological Survey (USGS) are using 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 are very sensitive to climate chaos. Higher temperatures and changes in precipitation over the last century appear to be contributing to an increase in glacier melting. Southern Alaska is also prone to earthquakes because a tectonic plate under the Pacific Ocean is pushing into its coast, building up significant pressure at critical points.
Ice is heavy and exerts enormous pressure on whatever lies beneath it. Under the ice’s weight, the Earth's crust bends and as the ice melts the crust bounces up again. Imagine a floating cork, topped with a piece of lead. Will it not pop upwards when the lead is taken off? Similarly, a shrinking ice cap reduces the pressure on the earth's mantle, causing it to melt and creating magma. Also, this frees tectonic plates up to move against each other and cause the friction needed to initiate earthquakes. This tallies with mathematical models that suggest such processes may potentially lead to more earthquakes, tsunamis and volcanic eruptions.
Research published in the scientific journal, Geophysical Research Letters, by the volcanologist Freysteinn Sigmundsson at the University of Iceland and the geophysicist Carolina Pagli at the University of Leeds in England, suggests that:
. About 10 percent of Iceland's biggest ice cap, Vatnajökull, has melted since 1890 and the land nearby has been rising about 25 millimetres (0.98 inches) a year, bringing shifts in geological stresses.
. Melting ice appears to be the main way in which global warming could have knock-on effects on geology.
. At high pressures, such as under an ice cap, rocks cannot expand to turn into liquid magma even if they are hot enough. As the ice melts the rock can melt because the pressure decreases.
. The effects would be biggest with ice-capped volcanoes. If the load of ice removed is big enough, this will have an effect at depths on magma production.
. As a result, there will be either somewhat larger eruptions or more frequent eruptions in Iceland in coming decades.
However, there is no sign yet that the current eruption from below the Eyjafjallajökull glacier in Iceland that paralysed flights over northern Europe for nearly a week was linked to global warming. The glacier is too small and light to affect local geology.
The volcanic eruptions could cool the planet. The sulphur dioxide that they fling into the stratosphere transforms into sulphuric acid droplets. This aerosol reflects sunlight so temperatures can drop. A far bigger explosion than the recent one in Iceland, at Mt Pinatubo in the Philippines in 1991, caused an average cooling of between 0.5 and 0.6 degrees centigrade in the Northern Hemisphere over the following year. Mexico's Mount Chichon eruption in 1982 also had a demonstrable cooling effect. As carbon dioxide and other green house gas emissions continued to build up in the atmosphere, the thermometer rose to compensate once the initial effects wore off. At this point, scientists think Iceland's eruption is too small to cause cooling although the massive disruption it caused to air travel in northern Europe may have significantly reduced aviation-linked carbon dioxide emissions.
Advocates of geoengineering, or manipulating climatic elements in order to slow climate chaos, have suggested mimicking the cooling effect of volcanoes by artificially spewing sulphur dioxide into Earth's atmosphere. However, one of the flaws in their argument, in addition to the need for an extremely long vertical hose, is that sulphur dioxide is not benign. The gas also causes acid rain and wears away the ozone layer, a key barrier to the sun's harmful rays.
Ecological and geological matters are tightly interlinked and affect all types of life on this planet: from single-cell organisms to the vast expanse of humanity distributed across the world. Slight interruption in the Earth's fragile balance can mean particular damage to the very mechanisms that embrace the lives of so many interdependent species. The recent Icelandic volcano eruption shows us just how fragile our modern, technologically dependent, systems really are. When was the last time a volcano on a small island brought a vast swathe of the modern world to a halt for nearly a week? The poet Robert Frost famously wrote, "Some say the world will end in fire; some say in ice." Volcanoes, earthquakes and glaciers are entangled in an elaborate web. We have to ask ourselves what type of contingency plans need to be put in place should similar events occur in the future. Survival depends on our civilisation's resilience in the face of adversity.
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