Thursday, October 13, 2011

Secret of catastrophic volcanic 'super-eruptions' that happen once every 100,000 years is unlocked - 13th Oct 2011

Reseachers have finally discovered the causes for 'super-eruptions' of volcanoes which are considered one of the most catastrophic natural events on Earth,

The violent explosions which occur about every 100,000 years are now thought to be caused by a combination of temperature and the geometrical configuration of the magma chamber in the volcano.

Scientists at Oregon State University presented the finding of their study, which was funded by the National Science Foundation, at the annual meeting of the Geological Society of America in Minneapolis.

Patricia Gregg, a post-doctoral researcher at OSU and lead author on the modeling study, said the creation of a ductile halo of rock around the magma chamber allows the pressure to build over tens of thousands of years, resulting in extensive uplifting in the roof above the magma chamber.

Eventually, faults from above trigger a collapse of the caldera and subsequent eruption.

She said: 'You can compare it to cracks forming on the top of baking bread as it expands,

'As the magma chamber pressurises at depth, cracks form at the surface to accommodate the doming and expansion.'

She added: 'Eventually, the cracks grow in size and propagate downward toward the magma chamber.

'In the case of very large volcanoes, when the cracks penetrate deep enough, they can rupture the magma chamber wall and trigger roof collapse and eruption,'

The eruption of super-volcanoes dwarfs the eruptions of recent volcanoes and can trigger planetary climate change by inducing Ice Ages and other impacts.

One such event was the Huckleberry Ridge eruption of present-day Yellowstone Park about two million years ago, which was more than 2,000 times larger than the 1980 eruption of Mount St. Helens in Washington. Read More