Mt. Fuji May Be Close To Erupting

SpuriousLogic points out an article at Wired discussing research into pressure levels inside Mt. Fuji's magma chamber, which scientists claim is higher than it was in 1707, the last time it erupted. "The new readings, taken by the National Research Institute for Earth Science and Disaster Prevention, reveal that the pressure is at 1.6 megapascals, nearly 16 times the 0.1 megapascals it takes to trigger an eruption." A series of earthquakes shook the area around Mt. Fuji a little over a decade ago, and a fault line was discovered underneath it. "Since the March 2011 tsunami and the 6.4 magnitude earthquake that followed four days later, Japan has been on tenterhooks, and in May 2012 a professor from Ryukyu University warned that a massive eruption within three years would be likely because of several major factors: steam and gases are being emitted from the crater, water eruptions are occurring nearby, massive holes emitting hot natural gases are appearing in the vicinity." While the rising pressure within the magma chamber is of concern, it is but one factor among many that lead to eruptions.

Re:"Nearly"?

[Calydor]

I'm curious, do you say, "I'll be there in 58 minutes and 48 seconds," or do you say, "I'll be there in an hour?"

I'm pretty sure both the .1 and the 1.6 megapascals is a rough estimate and not a 100% exact, set-in-stone figure.

Re:Drill a hole, relieve the pressure?

[oogoliegoogolie]

IANAV, but I would guess that a 30cm bore hole wouldn't have much of an effect on a magma chamber that is miles wide.

Re:What triggers an eruption?

[hawguy]

The new readings, taken by the National Research Institute for Earth Science and Disaster Prevention, reveal that the pressure is at 1.6 megapascals, nearly 16 times the 0.1 megapascals it takes to trigger an eruption

If that's what it takes to trigger an eruption, why didn't it happen 1.5 megapascals ago?

Probably the same reason why even though a cigarette is enough to trigger a gasoline explosion, people still manage to smoke while fueling their cars without blowing themselves up - a cigarette is sufficient to set it off, but it takes a combination of factors to make it happen.

Re:"Nearly"?

[flyingfsck]

I wonder how many people here are old enough to get your joke?

Re:how do they know

[ppanon]

They probably figured it out based on the pattern and quantity of ejecta. i.e. to launch boulder of this size this distance and to cover this area with this much ash then, assuming the lava reservoir was roughly the same size as it, the pressure needed to be X.