Slashdot Mirror
Mt. Fuji Volcano In 'Critical State' After Quakes
An anonymous reader writes: Mount Fuji, in addition to being a picturesque landmark and an important part of Japanese culture, is also an active volcano. Its last eruption was just over 400 years ago, but its location — where the Eurasian, Pacific, and Philippine tectonic plates meet — mean it will always have potential for eruption. A new study (PDF) has examined the pressures around Mount Fuji in the wake of several recent earthquakes, including the magnitude 9 tremor that unleashed the destructive tsunami in 2011. The researchers now say the volcano is in a "critical state." According to the study's lead author, "The volcanic regions are the ones where the fluids trapped in the rock – boiling water, gas, liquid magma, which cause an eruption when they rise to the surface – exert the greatest pressure. The seismic waves add to this pressure, causing even more disturbance." They have no way of predicting when an eruption might happen, but the potential seems greater than ever.
Part of the problem with trying to relieve the pressure is that many eruptions occur because of gases suspended in the magma. Once the pressure drops enough, the gas ceases to be soluble in the magma and it's the expansion of the gas that causes the violent eruption. It follows that relieving the pressure could easily trigger the eruption you are trying to prevent in this case. Whether this is the actual cause of an eruption in a specific case is dependent on the volcano, I believe, and is implicated in the more explosive ones, as opposed to the gentler flowing eruptions found with others.