The first to notice the growing crack in Rattlesnake Ridge was a local pilot, back in October.
Since then, geologists have been monitoring the area in Washington state, and report that 4 million cubic yards of land have moved in just a couple of months — faster than was expected.
As Anna King of the Northwest News Network reports, nearby residents are "weighing grim options: abandon house and home — or stay and risk their lives."
Residents told The Seattle Times they were haunted by what happened in Oso, Wash., in 2014, where 43 people were killed and dozens of homes were destroyed. Brian White, one of the state Department of Transportation administrators told reporter Erik Lacitis: "Everyone thinks about it."
Geologists disagree over how big the Rattlesnake Ridge slide will be, and whether it will speed up and grow, or stabilize itself. David Montgomery, a professor of geomorphology at the University of Washington, studies landslides, and says "this is a very interesting one."
"It's still moving quite slowly," Montgomery says. "It's a very different geological material than what we had in the tragic Oso landslide in 2014." He adds though that Oso was also considered a "low probability" event. "They're trying to assess, what's the worse case scenario?"
The "worst case scenario," it seems, is that the landslide could begin moving much more rapidly. If that were to happen, it could impact infrastructure, including the highway that runs through Yakima Valley.
Such predictions have alarmed residents who live in the quarry at the bottom of Rattlesnake Ridge. The Seattle Times reported Sunday that many have evacuated to motels. The Yakima Valley Office of Emergency Management is seeking foster homes for displaced animals, including eight small dogs and 100 chickens.
"It sounds to me like they're being fairly conservative in their response to it," Montgomery says of the geologists working on the case. "They should have a good handle on how the landslide is evolving and be able to evaluate how the nature of the hazard may be shifting."