Tuesday, July 22, 2014

New Round Of Warnings For Mt Fuji

Apparently the news media wants to remind you of the dangers posed by Mt Fuji, who's magma chamber has been pressurized to unprecedented levels following 2011's major 9.0 earthquake in Japan. A 6.4, and 5.0 quake followed, centered under Mt Fuji, which has caused some concern for scientists and nearby cities. I reported on this over two years ago, and while not much has changed, it seems that this is back in the headlines again, so I thought I'd set the record straight, lest the news media sends you into a panic.

Mt Fuji seen from Japan.

Here are some basic facts.

Yes, Fuji is under an immense, even record amount, of pressure in its magma chamber. The pressure is currently greater than it was during the 1707 eruption which blasted a massive crater in the SE flank of the mountain. This means that any further disturbances, such as medium to large quakes in the region could fracture rock, and allow for magma and gas to rise, raising the risk of a highly explosive eruption.

This is by no means imminent, as it is impossible to predict quake activity or location. It simply means that Fuji is primed, and large quakes close to the mountain would increase this risk. Right now, no seismicity other than normal background rumblings are occurring. So there is no need at this time to panic.

Japan has been criticized for its lack of disaster planning regarding Fuji, however last year they did release a new evacuation plan in the event of an eruption, which would likely give some warning in the form of increased tremor (long period quakes, rock fracture tremors, etc) and increased gas emissions.

The important thing for scientists, and Japanese residents is to simply remain aware and vigilant of the threat. Japan is still recovering from the aftermath  of the 2011 quake, tsunami, and nuclear meltdown of the Fukushima Daiichi power plant which was damaged by the quake. A massive volcanic eruption from Fuji IS in the future for Japan, it is only a matter of time. That time however is impossible to know. Fuji is capable of depositing significant amounts of ash as far away as Tokyo, so an eruption would have severe consequences for an island already stressed by other disasters.

But again, this is nothing new, and we have known that Fuji is primed for several years now. As I can attest looking at my traffic charts on my own blog, any news about Fuji, one of the worlds most famous volcanoes, is always a click-generator. It doesn't mean you shouldn't pay attention, but don't lose too much sleep over it.

Friday, July 11, 2014

Outburst Flooding From Katla Volcano Iceland [UPDATED 7/16/14]

It appears that Katla Volcano in Iceland, under the Myrdalsjökull ice glacier is experiencing heightened activity. Fellow volcano blogger Jon Frimann has posted that Iceland has raised the alert level to 'uncertain', as glacial outburst floods or 'jökulhlaups' have been occurring, in conjunction with rising conductivity levels in rivers, as well as gaseous hazards being reported.

Katla volcano had a minor eruption following the now-famous eruption of Eyjafjallajökull in 2010.

Current seismicity is concentrated within the Katla caldera underneath the glacier, and no eruptive activity on the surface is yet apparent.

It is too soon to say whether any activity will increase. Other areas in Iceland are showing increased seismicity, including the Askja system, and the Torafjökull volcanic system, however no eruptions have occurred in Iceland since mid 2011 when the last eruption of Grimsnes (Grimsvötn) occurred.

If any updates happen, I'll update this post.

*****UPDATE 7/16/14*****

A larger quake swarm is occurring within the Katla caldera. The largest quake, which occurred yesterday, was magnitude 3.1. While numerous, these small quakes do not represent anything truly immense at this point. It is possible that eruptions might begin at the volcano, but these would likely be small, and probably not energetic enough to break free of the glacier.

(Click to enlarge) Image from en.vedur.is/Iceland Meterological Office showing quake swarm in Katla caldera.

Iceland has lifted the 'uncertain' warning from Katla, however it is possible for jökulhlaups (glacier outburst floods) to occur with little warning. Given the activity, I'd steer clear of the volcano and associated watersheds until things calm down. Hazards include jökulhlaups, gases, and the possibility of explosive eruption (even if unlikely at this point).

I'm keeping my eye on this one for a while. Iceland has had a few years of relative calm (by relative, I mean nothing too explosive... the land there is always seething), which is always a little nervous. Iceland's many volcanoes are always a potential threat, and can erupt with little, or very subtle warning.

Thursday, July 10, 2014

Large Quake Swarm at Long Valley Caldera, CA

After a few months of relative quiet at California's Long Valley Caldera, East of Mammoth Mountain volcano, activity has intensified with hundreds of small and shallow quakes at depths of around 4.7 miles. Many small tremors are occurring below the surface about 1.5 miles north of Yosemite Mammoth Airport. These are small quakes, and likely not able to be felt by anyone not at the epicenters. These quakes are interesting mostly due to the sheer numbers, not the magnitude.

More than likely these are hydrothermal 'spasmodic' quakes, related to liquid movement under the surface, and likely not a result of any serious magma intrusion. If there were a large intrusion of magma, you would expect to see the depths of the quakes change (these are all relatively consistent) to progressively shallower depths. Since this isn't occurring, it is reasonable to assume this is simply normal behavior for Long Valley's large hydrothermal system, rivaled only by Yellowstone in the US.

Image from Google Earth with USGS overlay detailing locations of quakes in Long Valley.

The Long Valley caldera is a so-called 'supervolcano', like Yellowstone, or the Valles Caldera in Mew Mexico. Long Valley was the source of one of the largest eruptions on Earth, approximately 760,000 years ago, which created the voluminous Bishop Tuff, a layer of ash and debris that spans most of the continental US. Like Yellowstone, Long Valley is capable of 'nation ending' eruptions, however this, like Yellowstone, would be extremely unlikely in our lifetimes. 

The last 'serious' activity at Long Valley was a 6.0+ mag quake in the late 70's, which was followed by rapid 'doming' in the center of the caldera. On average this 'resurgent doming' has added several centimeters in height per decade.

It is likely in the future that activity will resume at Long Valley, given the doming, active geothermal system, and persistent seismicity. For now, I wouldn't lose any sleep over this, as it is not only quite common, but completely normal activity. If larger quakes were to 'swarm' in the area, this would be a cause for concern.

*****UPDATE 7/11/14*****

Looks like the swarm is over for now.