01 February 2010


Today's NYTimes reports that over the past several weeks, an average of 100 small earthquakes per day have been recorded, clustered in a remote area of Yellowstone National Park. It isn't news that Yellowstone is an active tectonic and geothermal zone. Another swarm of over 1000 quakes struck the area last year, and the largest recorded swarm happened in 1985 -- 3000 quakes over a period of three months.

Though such swarms may be relatively common, geologists are paying close attention, since this one coincides with a significant rise in elevation of the plateau over the Yellowstone Caldera (see diagram above). Much of the park is occupied by the dormant crater of a once-catastrophic volcanic eruption which took place around 640,000 years ago. The eruption spread ash and debris over much of the western United States (see comparison chart and map below).

Like Hawaii, Yellowstone lies over a volcanic hot spot. As the tectonic plate on which each area is located slowly moves over the stationary hot spot, the landscape is altered in a recognizable pattern. In Hawaii, each of the chain of islands is the result of a hot spot eruption (see first diagram below). In Yellowstone, the magnitude of each supervolcano has been much greater, with traceable results. The supereruptions of 640,000 years ago, 1.3 million years ago, and 2.1 million years ago, each produced a distinct caldera visible from space, as well as reducing a once-mountainous region to the modern Snake River Plain, which lies west of Yellowstone (see second diagram below).

There is no reliable method for forecasting when the next supereruption may occur. It could be tomorrow, or it could be in 10,000 years. But like the next monumental earthquake along the San Andreas Fault, it is one thing ............. inevitable.

No comments:

Post a Comment