ROCKVILLE, Utah (AP) — State geologists are conducting an extensive investigation at the scene of a rockslide that killed two people in a small Utah town outside Zion National Park to assess whether there’s any continuing risk.
Jessica Castleton of the Utah Geological Survey said the slide that destroyed a Rockville house and killed its residents inside, 65-year-old Maureen Morris and 58-year-old Jeff Elsey, can help her and other geologists determine when they are most likely to occur.
The geological survey has studied and mapped rockslide areas for years and each new event provides valuable clues, she said.
“These events can help us determine what causes these rock falls, how large they can be, if they tend to be a smaller scale in certain areas or larger scales in other areas, as well as their triggering factors (and) if they occur with freeze-thaw events or precipitation events,” Castleton told KSL.
“Sometimes rock fall occurs with no obvious triggering factor. So to try to determine when they’re most likely to occur is one of our main priorities,” she added.
Steve Bowman, manager of the geological survey’s Geologic Hazards Program, said geologists viewed the cliff above Rockville from a helicopter after the rockslide and believe the area is still active.
He said the most likely cause of the slide was the freezing and thawing of snow and ice that worked its way into cracks, causing several boulders as large as a delivery van to dislodge and fall hundreds of feet to the home below.
“Our geologists were able to get up in the air … and found boulders visually that looked like they could come down the slope. So we’re probably not out of the woods yet,” he told KSL.
It was the sixth massive rockfall in the town of 250 since October 2011, when a sleeping resident narrowly escaped injury as a 300-ton boulder destroyed a third of his house, The Salt Lake Tribune reported.
Rockslides are relatively common in Utah, and are most common after rain, earthquakes, and freezing and thawing, according to the geological survey.
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