Evidence of One of Earth's Largest Landslides Discovered in Utah

Researchers recently discovered evidence of one of Earth's largest landslides in Utah, and though a rare event, it can help shed light on what could happen in the future as a result of modern volcanic fields.

According to the study, published in the journal Geology, the Markagunt gravity slide took place more than 21 million years ago, and in a matter of minutes managed to destroy everything in its wake in southern Utah. The size of three Ohio counties, this landslide rivals the largest known on the surface of the Earth - the "Heart Mountain slide" in northwest Wyoming from 50 million years ago.

But once it's mapped in great detail, the Markagunt could prove to be much larger than the Heart Mountain slide.

"Large-scale catastrophic collapses of volcanic fields such as these are rare but represent the largest known landslides on the surface of the Earth," the authors wrote.

Geologists had already known of the existence of the Markagunt slide from millions of years ago, but they didn't realize the extent of this catastrophe until recent mapping was conducted. The results showed that the landslide covered about 1,300 square miles and itself was 55 miles long, proving that it was just as fast as it was massive.

Further evidence of the Markagunt slide's scale came from pseudotachylytes - rocks that were melted into glass by the immense friction created.

You would think that the enormity of this landslide would be obvious, however, "Looking at it, you wouldn't even recognize it as a landslide," lead author David Hacker, associate professor of geology at Kent State University, said in a statement.

But internal features of the slide found in outcrops expose evidence, such as jigsaw puzzle rock fractures and shear zones, along with the pseudotachylytes.

Researchers believe that the vertical inflation of deeper magma chambers, which feed volcanoes, caused this mega-landslide. And better understanding what causes these types of extreme events can help show geologists what could happen in the future, for example, as a result of volcanic fields like the Cascades.