"Any disaster fiend will tell you that Yellowstone National Park is long overdue for a monster eruption that could leave as much as half the U.S. under a blanket of ash. And there are rumblings the big one could be imminent in the wake of a series of 30-plus mini-earthquakes in the park over the past few days—too weak to be felt by humans for the most part but picked up by the seismometers at the University of Utah."
"After all, the geologic record shows that the giant caldera we affectionately call Yellowstone has blown every 600,000 years or so over the past 2 million years. The last big eruption? About 640,000 years ago when the park spit out about 240 cubic miles worth of rock, dirt, magma and other stuff."
Small earthquake swarms are not indicators of imminent volcanic eruptions, but harmonic tremors are. From USGS visual glossary:
harmonic tremor: Harmonic tremor describes continuous rhythmic earthquakes that can be detected by seismographs. Harmonic tremors often precede or accompany volcanic eruptions. The visual glossary has an example to look at, all the better to compare the harmonic tremors as seen on the University of Utah's seismos, which I posted earlier. Decide for yourself if they are ground quakes or magma tremors.
But here's from Rightpundits:
It should be noted that all the earthquakes have been intense and concentrated in one area, which happens to be above the magma chamber. [ see .gif below ] The scariest part of this story is the “harmonic tremors” that scientists have picked up. They are a low level constant rumbling, which usually indicates magma movement.Continuing the Scientific American excerpt:
"In recent years, Yellowstone's caldera has been rising thanks to uplifting magma beneath it—leading to more cracks, hot springs and even more frequent eruptions of Steamboat Geysers. Paired with the earthquakes, such magma movement might presage an eruption—either big or small. Unfortunately, scientists can't really predict when the next such eruption will happen, and the range of possibilities is large: from later today to a million years from now."
"How will we know if we should start worrying? The real warning signs will be rapid changes in the shape of the ground as well as volcanic gases leaking from the ground, neither of which have been sighted—yet."
If indeed the supervolcano is getting ready to blow, it does not necessarily have to be a supereruption. It could be a small one or it could by a hydrothermic event. Time will tell. Meanwhile, the unusual swarm continues. And is should be noted that a day and a half ago the USGS started pulling the eq's from their list and have not posted all of them that have occurred, according to other sites that have different seismographs and are noting more activity than USGS is publicly posting.
MAP 2.7 2009/01/01 12:51:24 44.548 -110.361 0.2 (38 mi) ESE of West Yellowstone, MT
MAP 2.4 2009/01/01 10:13:52 44.541 -110.389 0.2 (36 mi) ESE of West Yellowstone, MT
MAP 2.4 2009/01/01 10:12:57 44.325 -110.388 37.0 (42 mi) ESE of West Yellowstone, MT
MAP 2.3 2009/01/01 10:06:51 44.529 -110.370 0.5 (37 mi) ESE of West Yellowstone, MT
MAP 2.3 2009/01/01 10:02:57 44.528 -110.346 0.2 (39 mi) ESE of West Yellowstone, MT
MAP 1.6 2009/01/01 06:59:39 44.504 -110.340 0.9 (39 mi) ESE of West Yellowstone, MT
MAP 2.1 2009/01/01 05:29:09 44.507 -110.309 1.5 (40 mi) SSW of Cooke City-Silver Gate, MT
MAP 2.2 2009/01/01 05:19:51 44.509 -110.350 1.7 (39 mi) ESE of West Yellowstone, MT