Over the past several days, something that may just be very unusual has been occurring in ancient caldera in Yellowstone National Park. Over 250 micro earthquakes have occurred during that brief time, and while earthquake swarms are not uncommon in themselves, either at Yellowstone or other volcanoes, several aspects of this current swarm make it unusual, and therefore very interesting.
First, the many small earthquakes are not only occurring rapidly, but they are occurring in a very small area, less than one kilometer across. They are also happening in Yellowstone lake just below, and immediately around the location of a dome on the floor of the lake - discovered only recently.
Second, the quakes are generally very shallow. Several have been less than .3 kilometers from the surface, and the average depth is about 2.5 kilometers, which places them at about the same depth as the magma chamber that drives the geothermal engine at Yellowstone, fueling the geysers.
Third, the quakes are occurring within the caldera itself, while the smaller swarms of 1985, 1995 and 2004 all occurred outside the caldera, nearer to Hebgen lake. It is very likely that the quakes are related to magma movement through the geophysical system at Yellowstone, but it seems to be unclear to scientists at this time whether the quakes are a precursor to some sort of eruption, or just a particularly active set of routine quakes. said Robert Smith, a professor of geophysics at the University of Utah said that "they're certainly not normal", and added that "we might be seeing something precursory. "
In the past couple of years seismologists have inched closer to developing a predictive technique to allow warnings before eruptions. This technique was used to prevent loss of life in the eruption of Popocatepetl in 2000. It indicates that sometimes harmonic tremors and quake swarms can predict volcanic eruptions.
Likely the swarms at Yellowstone are just a larger than usual magma movement event, and no eruption is imminent. At least, we'd best hope so, because the world's largest supervolcano would almost certainly cause immeasurable destruction both in the area within 100 miles and indeed around the world. Some links to follow the action: