Earthquakes in Yellowstone: ‘Elevated but not unusual’

From <---> earthsky.org/earth

In recent weeks, there’s been a flurry of news about the volcanic system that lies beneath Yellowstone National Park, one of the best-loved parks in the United States. March 2014 saw swarms of earthquakes there, with 332 earthquakes striking Yellowstone last month.


 The largest event was a 4.8-magnitude quake on March 30. The U.S. Geological Survey released a special FAQ on April 2, 2014 about recent news reports on earthquakes, animal movement and more in Yellowstone.


Why is Yellowstone so geologically active? Yellowstone National Park sits on top of one of the most geologically active areas in North America, a hotspot in Earth’s crust. Yellowstone’s unique and beautiful landscape was largely formed through three powerful volcanic eruptions that occurred 2.1 million, 1.3 million, and 640,000 years ago. These eruptions left behind enormous calderas, which are bowl-shaped depressions that form when the mouth of a volcano collapses. This area of volcanic activity under the park is often referred to as the Yellowstone hotspot or Yellowstone supervolcano. Today, geysers, hot springs, mudpots and fumaroles (gas vents) dot the landscape in Yellowstone. Small earthquakes (less than 3.0 in magnitude) happen frequently in Yellowstone National Park, and these can be caused both by hot magma moving under the ground and tectonic movements of Earth’s crust along fault lines.

This histogram shows the last 20 years of earthquakes in north-central Yellowstone. Note the recent uptick in earthquakes (332 earthquakes in March 2014), and note other similar upticks in the past. Histogram via USGS.




Are 4.8-magnitude earthquakes common in Yellowstone The 4.8-magnitude earthquake that rattled the park on March 20, 2014, is a normal and frequent event on a geologic timescale, but not on a human timescale. An earthquake of this magnitude has not been observed in the park since the early 1980s. The epicenter of the quake was about 4 miles north–northeast of the Norris Geyser Basin. A preliminary analysis of the event suggests that the earthquake was of a tectonic origin and consisted mostly of strike-slip motion, according to a new report released on April 3, 2014 by the Yellowstone Volcano Observatory.

Map showing the locations of volcanic calderas in Yellowstone National Park, U.S.A. Image via USGS.

Do recent swarms of earthquakes in Yellowstone mean the supervolcano is about to erupt? No. The recent spate of seismic activity does not indicate the Yellowstone supervolcano is about to erupt. Even though another extremely large eruption is theoretically possible, an event of such magnitude is not likely to occur for several thousands of years, at least.That’s good, because such an event would obliterate the area surrounding the eruption within a radius of hundreds of kilometers, and cover the rest of the United States and Canada with multiple inches of ash, shutting down agriculture and causing global climate cooling for as long as a decade.

 

Source and credit to earthsky.org/earth