Creeping landslide devouring part of Wyoming town

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JACKSON, Wyo. (AP) - No one can say precisely when the mountainside collapsing into this Wyoming resort town will give way. But it appears increasingly likely that when it does, it’s going to take a piece of Jackson with it.

Workers and residents have watched helplessly in recent days as the slow-motion landslide spanning hundreds of yards split a house in two and inched ever closer to a cluster of businesses below.

Standing at the edge of the slide zone, its rocky slope rising sharply behind him, Jackson Fire Chief Willy Watsabaugh said the rate of movement slowed Saturday, giving crews a chance to get back in and reassess the damage.

Yet the fate of the businesses, houses and apartment buildings in the slide zone remained in doubt. Experts brought in to assist the town said it was unknown when the slide will come to a rest.

Efforts taken to stop it - including the erection of large concrete walls at the base of the slope - have proved futile.

The concrete walls had been pushed around by the shifting ground and were leaning away from the slope Saturday, when they were relocated to support a make-shift road being built to give heavy equipment better access to the site.

“We’re up against the Earth, and the Earth’s movement is an extremely powerful thing,” Watsabaugh said.

A sudden acceleration earlier in the week prompted authorities to suspend their efforts to shore up the slope as falling rocks created a hazard. The work that resumed this weekend focused on repairing some of the damage already inflicted, such as a break in a sewer line on Friday, town spokeswoman Charlotte Reynolds said.

What triggered the geologic event remains under investigation.

Authorities are looking into whether recent construction at the foot of East Gros Ventre Butte made the slope unstable. But they say there could be a variety of additional causes, including earlier construction at the site, warmer weather and a wet winter that put more water into the ground, where it acts as a lubricant for unstable rocks and soil.

Town officials first noticed significant hill movement April 4. They evacuated 42 homes and apartment units April 9.

By Saturday morning, the shifting earth had caused bulges in a road and a parking lot at the foot of the hill that were as big as 10 feet. The groundswell pushed a small town water pump building 15 feet toward West Broadway, the town’s main drag.

Because of its more stable geology, the slope is unlikely to suddenly collapse like the March 22 landslide in Oso, Wash., that killed 39 people, experts said. More likely, large blocks of earth would tumble down piece by piece.

The ground had been moving initially at a rate of an inch a day. That is expected to speed up as time goes on, said George Machan, a landslide specialist consulting for the town.

Rockslides are common in the surrounding Rocky Mountains in the spring, when melting snow and warmer weather unleashes the region’s dynamic geology. In the early 1920s, a massive slide caused by heavy rains north of Jackson formed a natural dam across a small river. The dam gave way two years later, unleashing a flood that killed six people.

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