SPRINGVILLE — New data released Tuesday shows a boulder rolled more than 2,000 feet and split into two before it crashed into the front porch of a home in Springville last month.
The rockfall happened during the evening on July 16. Jessica Castleton, a project geologist with the Utah Geological Survey, said the boulder dislodged from a band of limestone on the hillside above the city.
According to the Utah Department of Natural Resources, which tweeted a video showing the route of the boulder, it bounced over a cliff, landed 142 feet from where it had catapulted into the air before it split in two down the mountainside. One boulder traveled 633 feet from that site and came to a rest in some brush. The larger piece smashed into a landscape boulder and then went between two properties before it came to a rest at the front porch of a home.
In all, the boulder traveled 2,270 feet, or nearly half a mile down a 1,020-foot slope from where it began, officials said.
Pat Knowlden, who lives at the home that the rock stopped in front of, told KSL TV on July 17 that she and her husband were at home at the time the boulder crashed into their porch.
“We heard this horrendous noise. I couldn’t figure it out, what it was, because it wasn’t, you know, a noise we’re familiar with,” she said.
When they looked outside to see what made the sound, they were surprised to find the boulder just outside their front door. No injuries were reported from the rockfall.
At one point the rock from last month's @SpringvilleCity rockfall was airborne for 142 ft, broke in two pieces and traveled just under 1/2 mile. The potential for hazardous rockfalls need to be better understood as development expands further into the foothills. @utahgeologicalpic.twitter.com/E0xWbT0fef— Utah DNR (@UtahDNR) August 20, 2019
Castleton said the neighborhood was lucky in that nobody was hurt and it only caused cosmetic damage the area.
“There have been rockfalls in Utah County along that same band — similar outcropping rocks — where the rocks have crashed through homes and caused significant damage,” she said. “It hit a landscape boulder in the backyard of one of the homes, and that threw its trajectory off so that it went in between the homes instead of going toward (the home where the landscape boulder was). It’s really just a matter of luck, the boulder shape, how fast it's going; and their paths are really unpredictable. It’s extremely fortunate nobody was hurt and no houses were hit.”
The data released Tuesday not only showed the path of the boulder but also how difficult it is to stop a rolling boulder. Department officials had previously stated the boulder was traveling about 50 mph by the time it entered the neighborhood from the mountainside.
So, how can homeowners and those out around cliffsides prevent injury or damage from boulders?
Castleton said Utahns can find rockfall or other geological hazard studies for the area where their home is from either the town or county they live in, or by contacting the Utah Geological Survey. She added homeowners may want to consider talking with local officials to see what could be done to mitigate rockfall risk where they live.
Since Utah is home to frequent outdoor activities, she pointed out there can be a rockfall risk for campers too. In fact, she said there have been a little more than a dozen rockfall deaths in the state.
“A large number of those are when people are camping close to cliffs, camping in areas where there are large rocks around. There’s always a potential for a rock to dislodge and fall,” Castleton said. “So when you’re out recreating and camping overnight, always look around you. Notice what’s happening and make sure you’re sleeping in a safe place away from areas where rocks can fall.”
As for when rockfalls like what happened on July 16 are more likely to occur, Castleton said large rainstorms increase the risk for rockfalls. There’s also a higher risk for rockfalls during spring and fall when water freezes and thaws in daily cycles throughout those seasons.