If any of Yellowstone's vast bison herds trembled in the last week, it wasn't from the cold: Seismologists recorded over 400 earthquakes within the park's borders in that same period. Swarms of tremors have happened in Yellowstone before, but rarely with as much frequency or strength.
It shouldn't come as much of a surprise, since Yellowstone sits atop North America's largest supervolcano. The same volcanic and geothermal forces that power the park's popular mudpots, geysers, and heated pools could one day erupt in a cataclysmic explosion as it did 640,000 years ago.
But park scientists like geologist Hank Heasler aren't worried about that happening anytime soon. Instead, they hope to find the source of the earthquakes and learn more about the astounding geological forces at work. The most powerfual quake so far only registered a 3.9 on the Richter scale, but it could be felt 30 miles away at Old Faithful.
The tremors haven't caused any damage or injuries, but they can annoy the rangers and scientists who live and work in the park:
"[Rangers] have commented to me that they would appreciate it if the earthquakes would stop so they could get a good night's sleep," [Heasler] says.
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