When the Ice Melts, the Earth Spews Fire

Dec. 19, 2012 — It has long been known that volcanic activity can cause short-term variations in climate. Now, researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel (Germany), together with colleagues from Harvard University (Cambridge, Massachusetts, USA) have found evidence that the reverse process also occurs: Climate affects volcanic activity.

 Villages near the Philippine volcano, Pinatubo, were devastated in 1991 when the volcano erupted. But the villages were not the only people affected by the eruption. The volcano threw enough ash and soot into the atmosphere to cause the global temperatures to drop by half a degree for the next couple years. We know that volcanic eruption can cause a short-term impact on climate, but climate could also affect volcanic eruptions globally, and over long periods of time. Strong evidence of climate effecting volcanos was found around the Pacific Ocean, covering the past 1 million years.

“"Among others pieces of evidence, we have observations of ash layers in the seabed and have reconstructed the history of volcanic eruptions for the past 460,000 years,"

"There were periods when we found significantly more large eruptions than in others" says Kutterolf, the lead author of the Geology article. After comparing these patterns with the climate history, there was an amazing match. The periods of high volcanic activity followed fast, global temperature increases and associated rapid ice melting.”

When they studied other cores from the whole pacific area, the same pattern was found.

“Geologists and geophysicists searched for a possible explanation. "In times of global warming, the glaciers are melting on the continents relatively quickly. At the same time the sea level rises. The weight on the continents decreases, while the weight on the oceanic tectonic plates increases. Thus, the stress changes within in the Earth to open more routes for ascending magma" says Dr Jegen.”

The rate of global cooling at the end of the warm phases is much slower, so there are less dramatic stress changes during these times. “"If you follow the natural climate cycles, we are currently at the end of a really warm phase. Therefore, things are volcanically quieter now. The impact from human-made warming is still unclear based on our current understanding" says Dr Kutterolf.” The next step is to investigate shorter-term historical variations to better understand implications for the present day.

http://www.sciencedaily.com/releases/2012/12/121219133551.htm