It Shook the Midwest: #ThisWeekInWyHistory

A view of the colorful, hydrothermal soil surrounding the turquoise waters of West Pyrite Pool at Bumpass Hell in Yellowstone National Park

It was a calm, peaceful Thursday afternoon. Birds softly chirped their songs amid babbling brooks as a gentle breeze kissed the treetops of Yellowstone National Park.

Joe Carder, of the National Park Service, had just settled down to enjoy his lunch in a park building on what was setting up to be another perfect day. Then the floor started to quiver, bucking beneath his feet as if a freight train had miraculously appeared in the wilderness and was on the verge of crashing through the walls.

Hundreds of miles away, residents of Great Falls, Bozeman, and Billings would later report feeling a series of earth tremors.

Carder recognized what it was in a heartbeat, and it wasn’t a freight train.

On December 9, 1975 news agencies across the Midwest released coverage of a far-reaching earthquake with the strongest tremor reaching a magnitude of 6.2 on the Richter Scale in Yellowstone National Park.

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The epicenter of the earthquake was located approximately five miles east-southeast of Norris Junction in Yellowstone National Park, an estimated 50 miles from that of the devastating 1959 Yellowstone earthquake that reshaped the landscape, formed a new lake, and claimed the lives of 28 people.

Thankfully, no one was injured in the 1975 earthquake and the damage was minimal, news agencies reported. The park service worked to clear a major park road that was blocked by a minor landslide and telephone service was temporarily down in West Yellowstone, Old Faithful, and Madison.

The 1975 earthquake was not the only one that year. A small seismograph stationed near Old Faithful geyser reportedly recorded over 2,000 minor earth movements that year, including one that measured 5.5 on the Richter scale.

But the 1975 earthquake was certainly one of the strongest, shaking windows and buildings across 31,000 square miles, according to the University of Utah.

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Every year, Yellowstone reportedly experiences around 1,500 to 2,000 earthquakes. Last month alone, a seismograph at the University of Utah recorded 100 earthquakes in Yellowstone, one of which reached a magnitude of 3.1 recorded nine miles north-northeast of West Yellowstone, Montana.

It’s a stark reminder that Yellowstone, while certainly beautiful to behold, is technically classified as an active super volcano, having erupted at least three times in the last 2 million years, according to Yellowstone National Park.

In order to be classified as such, a super volcano must have an eruption of magnitude 8 on the Volcano Explosivity Index. This means the volcano must erupt more than 250 cubic miles of magma.

The most recent eruption is believed to have occurred around 640,000 years ago and was 2,500 times larger than the May 18, 1980 eruption of Mt. St. Helens, according to Yellow Stone National Park.

It is the magmatic heat that powered that eruption in Yellowstone that still powers the park’s famous mud pots, hot springs, fumaroles, and geysers today.