Sunday, April 13, 2014

The Yellowstone Super-volcano

The number of Earthquakes at Yellowstone has increased. In March 30,  2014 Yellowstone experienced the largest Earthquakes since 1980 - it had magnitude 4.8, which is not high as far as Earthquakes go. However, the magnitude of the earthquakes that precede volcanic activity does not have to be high.  Information about the volcanic activity at Yellowstone can be found at Yellowstone observatory site. Note that they say that the increase in the number of Earthquakes is not particularly unusual. In the figure on the left the Earthquake count is cumulative, which means it can never go down and it would be constant only if no new Earthquakes occurred.

Increase in uplift
Status updates on the Yellowstone volcano can be found at its USGS site. The ground rises in volcanic areas due to magma activity underground.  Decompressions also happen, meaning the ground level lowers. The level of the ground is measured with GPS receivers and also from images taken via the Interferometric synthetic aperture radar. There was no measurable deformation associated with the March 30 earthquake. However, the GPS data has to be integrated over periods of a year or so to reach cm accuracies. They say the caldera has been rising at a rate of 2 cm/year, and that one of their ground stations has moved 5.5 cm up since April 2013. There are also movements of a few cm East and North. (I have also read that there are places where the ground has risen as much as 25 cm, but I still have to find a reliable reference for that.)
The Yellowstone Caldera. Image from

Increase monitoring via atomic clocks?
Atomic clocks can provide local measurements of the geoid over at cm level periods of a 7 hours. This is superior to the yearly measurements by GPS and in the future, atomic clock measurements might help in understanding the correlation between Earthquake and volcanic activity. However, the best clocks to date are still laboratory devices that are not yet ready for field work.

Animals leave the mountain?
There are movies youtube with bisons leaving Yellowstone. However, it is said that the migration pattern is not unusual (e.g, the animals have always come down the mountain when the food was scarce), and that the coincidence with the increase in Earthquake activity is just a coincidence. Apparently the bisons come down the mountain to scratch themselves on fire hydrants and buildings. It would seem a dangerous and pointless adventure to me if I was a bison and there were trees around, but then I am not a bison or an expert in bison behaviour.

When was the last time the Yellowstone Supervolcano erupted?
The largest large eruption of Yellowstone occurred some 650, 000 years ago. A smaller eruption happened about 70, 000 years ago.

What are the potentials of an Yellowstone eruption?
A super-eruption would be very dangerous. Besides destroying a good fraction of the US, it could induce a mini ice age lasting for a few hundred years that would change life on Earth as we know it.

Which man-made activity could increase the Earthquake count?
Hydraulic fracturing is a relatively new method that the US has been using to extract natural gas & oil. It involves fracturing the rock by injecting water at high pressure to reach the gas reserves. For maps that show were hydraulic fracturing is done in the US see: They come fairly close to Yellowstone.

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