Tuesday, March 15, 2011

Welcome to the machine

Some things make me sick. I have had some real bad luck lately with some people in my life lately.

I wish the world was as pure as a song, as good as lifelong friends, bt it isn't. Not even close.

I try to cocoon myself from it all by living as far from civilization as possible, numb myself to the weekday, careening down a mountain as fast as I can, enjoying a good meal, losing myself in a book or a movie, or by making music with my friends.

On the other hand, I am sitting basically right on top of the world's largest supervolcano, with a 35 by 45 mile caldera that is about 50,000 years overdue for its regularly scheduled eruption.

Yellowstone, like Hawaii, is believed to lie on top of an area called a hotspot where light, hot, molten mantle rock rises towards the surface. While the Yellowstone hotspot is now under the Yellowstone Plateau, it previously helped create the eastern Snake River Plain (to the west of Yellowstone) through a series of huge volcanic eruptions. Although the hotspot's apparent motion is to the east-northeast, the North American Plate is really moving west-southwest over the stationary hotspot deep underneath.

Over the past 17 million years or so, this hotspot has generated a succession of violent eruptions and less violent floods of basaltic lava. Together these eruptions have helped create the eastern part of the Snake River Plain from a once-mountainous region. At least a dozen of these eruptions were so massive that they are classified as supereruptions. Volcanic eruptions sometimes empty their stores of magma so swiftly that they cause the overlying land to collapse into the emptied magma chamber, forming a geographic depression called a caldera. Calderas formed from explosive supereruptions can be as wide and deep as mid- to large-sized lakes and can be responsible for destroying broad swaths of mountain ranges.

The loosely defined term 'supervolcano' has been used to describe volcanic fields that produce exceptionally large volcanic eruptions. Thus defined, the Yellowstone Supervolcano is the volcanic field which produced the latest three supereruptions from the Yellowstone hotspot. The three super eruptions occurred 2.1 million, 1.3 million, and 640,000 years ago, forming the Island Park Caldera, the Henry's Fork Caldera, and Yellowstone calderas, respectively.

The Island Park Caldera supereruption (2.1 million years ago), which produced the Huckleberry Ridge Tuff, was the largest and produced 2,500 times as much ash as the 1980 Mount St. Helens eruption. The next biggest supereruption formed the Yellowstone Caldera (640,000 years ago) and produced the Lava Creek Tuff. The Henry's Fork Caldera (1.2 million years ago) produced the smaller Mesa Falls Tuff but is the only caldera from the SRP-Y hotspot that is plainly visible today.

Due to the volcanic and tectonic nature of the region, the Yellowstone Caldera experiences between 1000 and 2000 measurable earthquakes a year, though most are relatively minor, measuring a magnitude of 3 or weaker. Occasionally, numerous earthquakes are detected in a relatively short period of time, an event known as an earthquake swarm. In 1985, more than 3000 earthquakes were measured over several months. More than 70 smaller swarms have been detected between 1983 and 2008. The USGS states that these swarms could be caused more by slips on pre-existing faults than by movements of magma or hydrothermal fluids.[14][15]

In December 2008, continuing into January 2009, more than 500 quakes were detected under the northwest end of Yellowstone Lake over a seven day span, with the largest registering a magnitude of 3.9.[16][17] The most recent swarm started in January 2010. With 1620 small earthquakes between January 17, 2010 and February 1, 2010, this swarm was the second largest ever recorded in the Yellowstone Caldera. The largest of these shocks was a magnitude 3.8 on January 21, 2010 at 11:16 PM MST.[15][18] This swarm reached the background levels by 21 February.