The basic evidence for the discovery came from the work of
the Collaborative Research Center "Fluids and Volatiles in
Subduction Zones (CRC 574) Collaborative Research Center-574.
For more than ten years the project has been extensively
exploring volcanoes of Central America.
"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,"
says GEOMAR volcanologist Dr Steffen Kutterolf, who has been
with CRC 574 since its founding. Particular patterns started to
appear. "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.
Subduction Zone and Volcanoes Video:
http://bit.ly/Wv58Js
Together with colleagues at Harvard University, the
geologists and geophysicists searched for a possible
explanation. They found it with the help of geological computer
models. "In times of natural warming trends, 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.
To expand the scope of the discoveries, Dr Kutterolf and
his colleagues studied other cores from the entire Pacific
region. These cores had been collected as part of the
International Integrated Ocean Drilling Program (IODP) and its
predecessor programs. They record more than a million years of
the Earth's history. "In fact, we found the same pattern from
these cores as in Central America" says geophysicist Dr
Marion Jegen from GEOMAR, who also participated in the recent
study.
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
man-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.
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