But other factors appear to be in play on East Gros Ventre Butte, a small mountain that looms over the west side of town, its base dotted with homes and businesses.

The area of the landslide has been graded for roads and businesses in recent years, including a new Walgreens. That could have weakened the hillside and set the stage for the landslide, although the precise trigger remains under investigation.

Jackson resident Rick Johnson lives less than a quarter-mile from the slide area along the same south-facing slope. He said a retaining wall on his property has been shifting in recent years, but he had not given it too much thought until the slide started just down the road.

As he watched workers at the top of the slide area taking measurements of the previous night's movements, Johnson said he had no doubt that the natural geologic forces at work were amplified by the recent construction of a Walgreens at the foot of the slide.

"I think they are just messing with Mother Nature, and they didn't think of the long-term consequences," he said.