Earthquakes. Supervolcanoes. Calderas. The End of Civilization. Not the usual subject matter of this blog, but I go where the news takes me. I just checked the last data from the University of Utah's seismograph station in Yellowstone. The earthquake swarm seems to have reintenstifieda bit over the past 24 hours. During Dec. 27 and 28, there was a swarm of earthquakes under Yellowstone in the 3.0-3.9 range. Activity then dropped off to quakes less than 2.0 on the Richter magnitude scale. But now we are again seeing quakes above 2.0 and even a 3.5 shaker earlier this morning. Again, the University of Utah puts this all in perspective:
The University of Utah Seismograph Stations reports that a notable swarm of earthquakes has been underway since December 26 beneath Yellowstone Lake in Yellowstone National Park, three to six miles south-southeast of Fishing Bridge, Wyoming. This energetic sequence of events was most intense on December 27, when the largest number of events of magnitude 3 and larger occurred. The largest of the earthquakes was a magnitude 3.9 (revised from magnitude 3.8) at 10:15 pm MST on Dec. 27. The sequence has included nine events of magnitude 3 to 3.9 and approximately 24 of magnitude 2 to 3 at the time of this release.
A total of more than 250 events large enough to be located have occurred in this swarm. Reliable depths of the larger events are up to a few miles. Visitors and National Park Service (NPS) employees in the Yellowstone Lake area reported feeling the largest of these earthquakes.
Earthquakes are a common occurrence in the Yellowstone National Park area, an active volcanic-tectonic area averaging 1,000 to 2,000 earthquakes a year. Yellowstone's 10,000 geysers and hot springs are the result of this geologic activity. A summary of the Yellowstone's volcanic history is available on the Yellowstone Volcano Observatory web site (listed below). This December 2008 earthquake sequence is the most intense in this area for some years and is centered on the east side of the Yellowstone caldera. Scientists cannot identify any causative fault or other feature without further analysis. Seismologists continue to monitor and analyze the data and will issue new information if the situation warrants it.
And here is what the Discovery channel has to say about Yellowstone and other supervolcanoes:
One way of looking at the power of volcanoes is what scientists call the Volcano Explosivity Index (VEI) — sort of a Richter scale for eruptions. And like the Richter scale used to measure earthquakes, the power of an eruption increases exponentially from number to number in the VEI index.
The VEI scale runs from zero to eight. The higher the VEI number, the bigger — and less frequent — the eruptions. On one end there are the burbling, rather gentle eruptions that happen on the big island of Hawaii. These happen daily on Earth, and even with their occasional impressive fountains of lava, they rate a zero on the VEI.
At the other extreme is the Yellowstone eruption of 2.1 million years ago, which is described on the VEI as an eight: mega-colossal, with a towering ash cloud 10 miles high that pours out at least a thousand cubic miles of ash. That Yellowstone eruption had 10 times the ejected material as a VEI 7 volcano, which modern humans have never seen either.
In fact, the last VEI 7 eruption was in Toba, Indonesia, 74,000 years ago, and it caused such global cooling that some scientists think it nearly drove humans to extinction.
The largest known eruption in the last several thousand years is believed to be that of Tambora, Indonesia, in 1815. It was tens of times more massive an eruption than Mount St. Helens in 1980. Despite pouring out 7 cubic miles of ash and causing short-term global cooling, Tambora was small fry compared with any of Yellowstone's big eruptions, or even the eruption of Toba 74,000 years ago.
No eruptions of this magnitude have happened since the dawn of civilization, about 10,000 years ago — which is lucky for us, and perhaps one reason civilization has been able to develop.