A supervolcano is one that explodes in (natch) supereruptions. Definitions vary, but usually we’re talking a magnitude-eight (M8) eruption: one trillion metric tons of ash and other debris filling at least 100 cubic miles, typically upchucked over the course of about a week. Picture 1,000 Mount Saint Helenses, or 8 Tamboras. Besides causing regional devastation, supereruptions affect global climate. An Indonesian super 74,000 years ago kicked off a thousand-year drought that some contend caused a human population crash.
Yellowstone is both a supervolcano and a hotspot; the two don’t always go together. A hotspot is the business end of what’s known as a mantle plume, a stream of magma that rises hundreds of miles through a channel in the earth’s crust. The Yellowstone plume head, 50 miles underground, is several hundred miles wide. Over time, the hot head melts the overlying crust, forming a smaller magma chamber. Yellowstone’s magma chamber is just a few miles down and contains partially melted granite viscous enough to trap gas, allowing pressure to build. Periodically the pressure cracks the surface, ejecting gas and disintegrated rock into the surface world. After about a tenth of the chamber’s contents have erupted, pressure falls and the show’s over. Reheat and repeat.
The Yellowstone hotspot has produced dozens of large eruptions over the past 16 million years, the last three within the Yellowstone volcanic field: two supers and one M7.4 lightweight that created 68 cubic miles of debris. They left overlapping giant calderas, or craters, each 10 to 50 miles wide. Since filled with lava and eroded, the calderas went unrecognized till the 1960s.
Hundreds Of Earthquakes Have Yellowstone Trembling
Probably the only thing we remember from our tours of Yellowstone a couple years ago are guides telling us about the supervolcano that formed the caldera that covers a large chunk of the national park. You can't have geysers and bubbling mudpots without lots of geothermal activity underground, and so Yellowstone is used to the occasional quake. But a recent batch of hundreds of mini-earthquakes, has scientists scratching their heads.
Though even the strongest of the tremors, at magnitude 3.8, is just strong enough to be easily noticed without seismic equipment, the fact that more than 250 quakes have occurred in the past few days has geologists on high alert, one University of Utah professor tells the AP:
This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to. We might be seeing something precursory.
Could it develop into a bigger fault or something related to hydrothermal activity? We don't know. That's what we're there to do, to monitor it for public safety.
While it's good to know someone's watching out for park visitors, it's not exactly clear what precautions could be taken if a massive earthquake were to suddenly hit. In 1959, a huge quake triggered a landslide that killed 28. The good news is that these quake swarms happen pretty often, so it could just be a little something to add some edginess to your national park visit.
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