Geologists working in southwestern Utah have discovered the remnants of a catastrophic landslide — one of the two largest known on demesne — that have place within minutes around 22 million years ago . Called the Markagunt somberness sloping trough , it extended over an area prominent than 3,400 square klick . That ’s about the sizing of Rhode Island , three counties in Ohio , or 39 Manhattans .
Smaller constituent of the Markagunt landslip have previously been key out , but its enormous extent was n’t revealed until these young map efforts . accord to a triplet of investigator led byDavid Hacker from Kent State , the 90 - kilometer - long chute mass had a volume of up to 2,000 cubic kilometers : It was as tight as it was monumental . voice of it were 200 meter thick . Thefindingswere published inGeologythis calendar week .
The landslip lead place in an area between what ’s now Bryce Canyon National Park and the townsfolk of Beaver , Utah , though you ca n’t see much of the slide today . “ Looking at it , you would n’t even recognize it as a landslide , ” Hacker says in anews release .
But intragroup feature — which were exhibit in outcrop — testify grounds of a landslide in the kind of jigsaw puzzle rock ‘n’ roll fractures , shear zones , and pseudotachylytes . The latter are rocks that melt into methamphetamine hydrochloride because of immense friction , and their presence suggests that the slide occurred within minute . Anything living in its path would have been wipe out .
Pictured to the right field , Hacker points to pseudotachylyte bed and vein within the Markagunt sombreness slide . Material from the landslide — shattered rocks , lava flow , volcanic mudflow , sandstone , and ash tuff — were sandwiched between well - studied layers of volcanic ash tree , which allowed the investigator to date the catastrophe .
The slide rise when the Marysvale volcanic field — consist of many strato - volcanoes similar toMount St. Helens , which erupt in 1980 — break down , yield way to the monolithic landslide . The flop may have been due to the erect pomposity of mystifying magma chambers , which prey the volcanoes . Molten rock rise toward the surface could have press the flanks of the volcano upward and sideway , fracturing tilt and creating unstable piles of stuff right for a landslide , discipline cobalt - authorRobert Biek of Utah Geological Surveytells Science .
Only one other continental landslip challenger Markagunt in size ( bigger slides do survive on ocean floor ) . The Heart Mountain playground slide , which was discovered in the 1940s , read spot around 50 million eld ago in northwestern Wyoming . Once it ’s mapped in slap-up detail , Markagunt could prove to be much larger than the Heart Mountain lantern slide .
Mega landslides like these help researchers understand extreme , hazardous events . Not to mention , both the Markagunt and the Heart Mountain slides helped document , for the first time , how prominent portions of ancient volcanic fields have collapsed ; they show the order of magnitude of what could happen in modern volcanic fields like the Cascade Mountains , nursing home to Mount St. Helens .
The team will stay on to map the slide , collect samples from the base for morphologic analysis , and date the pseudotachylytes .
Images : Google Earth viaAmerican Geophysical Union blog(top ) , Kent State University ( mediate )
