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Three experts from the U.S. Geological Survey arrived here Monday to study the rockslide that continues to bury a section of Highway 140 under a growing layer of rocks.
Their arrival, though somewhat slowed Monday by a plane delay, excited those who have been trying to find answers for the natural disaster that has already cost Mariposa County as much as $4 million in tourist revenue.
"These kind of rockslides are rare enough that they invite the greatest minds in the world," Yosemite National Park spokeswoman Adrienne Freeman said. "And that's who's here now. ... The truth is, we could spend all day speculating on what could happen. But we won't know until we hear the answers from these geologists."
Since the rockslide began April 29, a handful of other geologists have studied what has now been dubbed Ferguson rockslide.
But the three who arrived Monday — two are from Denver; one from Menlo Park — will be able to turn their research into three-dimensional models, working with the same equipment used to study volcanoes, Freeman said.
"They'll use some really interesting technology," Freeman said. "Their goal is not to clear the road. They're here to put a long-term response plan intact."
The USGS experts will spend at least two days here. Today, they will survey the rockslide from a U.S. Park Service helicopter with some other geologists who have been working on the disaster.
Monday afternoon, the three scientists arrived at Ferguson rockslide wearing hard hats. In two or so hours there, several large groups of rocks pounded down the slope in front of them.
"Today is just getting acquainted with the slide," said Jerry DeGraff, a U.S. Forest Service geologist who has been assigned to study the rockslide for the past week.
DeGraff said the three scientists have two objectives: to create the three-dimensional models to predict how the Merced River would react to being blocked and to closely monitor the rockslide's movement to learn what it's going to do in the future.
"The goal is, by the end of the week, to have some conclusions," Freeman said. "Nobody knows what's going to happen here. Hopefully, if we can outline specifically how this slide is moving, we can make some plans for how to deal with it."
DeGraff said the rock-falling activity has trailed off since a week ago. Monday, he said, rocks tumbled down about every half hour, compared with last week's rate of every five to 10 minutes.
He and other geologists spent the past week trying to determine what would happen if the river, which runs along the highway, were blocked by walls of rock that were either 50, 100 or 350 feet high.
"We were looking at the emergency-response needs rather than the long-term solution," DeGraff said. "We needed to make sure the initial disaster didn't become an even greater disaster."
The geologists determined the 350-foot scenario wasn't possible, but if 100-foot rock wall became a reality, the water would create a reservoir that would extend upstream as far as Cedar Lodge. DeGraff also said the nearby community of Savage Trading Post would be most affected.
A presentation about the rockslide will be delivered at the Mariposa County Board of Supervisors at the board's weekly meeting.
"It's more of a show-and-tell," Freeman said. "This is what's happening; this is what's happened; this is the goal for the future."
Two public meetings also are scheduled this week to keep local citizens abreast of the news. They will be at 7 p.m. Wednesday at Yosemite Bug Hostel in Midpines, and at 6 p.m. Thursday at El Portal Community Hall.
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