The big slide near Collbran in 2014 was massive enough to be seen from space, and get the attention of the National Aeronautics and Space Administration (NASA).
https://earthobservatory.nasa.gov/images/83883/mudslide-near-collbran-colorado
"On Sunday, May 25, 2014, a large mudslide rushed down a Colorado mountain near the town of Collbran covering an area three miles long and one-half to three-quarters of a mile wide. It claimed the lives of three ranchers and triggered a small earthquake," according the NASA Earth Observatory.
Two years later, Jesse Paul, in a article in The Denver Post published Feb. 29, 2016, reported the landslide that killed three men was caused by rain over melting snowpack, triggering a series of earth movements that began 10 hours earlier.
“Our results revealed that the rock avalanche was a cascade of landslide events, rather than a single massive failure,” said the study led by Jeffrey Coe, a research geologist with the U.S. Geological Survey.
The 2.8-mile-long West Salt Creek landslide on the Grand Mesa on May 25, 2014, was the longest such slide in Colorado history, the Post described.
"The report found the sequence began with an early morning rockfall event that combined with a later earth failure," wrote Paul.
The slide near the town of Collbran lasted about 3.5 minutes and sent a wall of debris rocketing down from the Grand Mesa.
“If precursor events, such as the one at West Salt Creek that occurred (before) the main avalanche, could be seismically detected and placed in the proper context, they could possibly be used for avalanche warnings,” the report said.
The men who died in the slide had gone up to find out why irrigation water below the slope that gave way had stopped running, said Jesse Paul, of the The Post.
Coe says that irrigation ditch had likely been plugged by the rockfall 10 hours before the main slide.
“To really be able to use that precursor event for warnings, we’d need a much more detailed seismic network than we have in the U.S.,” Coe told The Denver Post.
Coe explained there are proposals for such systems in some landslide prone areas, but not on the scale needed to provide universal coverage.
“I think we’re a ways off from any kind of dense network,” he said. “That kind of infrastructure just isn’t currently available and the cost would be very substantial.”
The extent of the mudslide is evident in the top image, which was acquired by the Landsat 8 satellite on June 7. The lower image, taken by Landsat 8 on June 20, 2013, shows the slide region before the slide. The top edge of the slide, the scarp, is on the lower side of the image. The debris flowed north and ended at the toe, partially covering a natural gas well.
"The slide happened in the Grand Mesa region of western Colorado, an
area extremely prone to landslides. In fact, the recent mudslide began
at the scarp of a previous landslide. The region is unstable because of
its underlying geology.
A layer of basalt lies on top of soft claystone that erodes easily. The
basalt slumps when water erodes the soft rock beneath it, as
illustrated in these diagrams.
Landslides are most prevalent in this region during the spring and
early summer when the ground is moist from snowmelt and runoff," according to NASA
Colorado experiences thousands of landslides every year. According to the Colorado Landslide Inventory, most of the slides occur in the mountainous western half of the state.
NASA Earth Observatory images by Robert Simmon, using Landsat 8 data from the USGS Earth Explorer. Caption by Holli Riebeek.
Following is a brief description of what happened on that day, as reported by the Grand Junction Sentinel.
The natural disaster happened on May 25, 2014. The below information is based on a 2015 Colorado Geological Survey/Colorado School of Mines publication issued in 2015, including police/witness reports contained in that publication's appendices. Material from Daily Sentinel coverage at the time also supplements this account.
■ Between 6 and 7 a.m., Melvin "Slug" Hawkins began hearing a strange "hissing" noise in the West Salt Creek drainage. He suspected a problem at one of the natural gas well pads in the area, but after driving to one of the pads found no problem.
■ A small seismic disturbance was detected at 7:18 a.m. by a seismometer 20 miles southeast of the landslide site. It may have recorded precursor landslide activity Hawkins observed that morning at a prehistoric landslide site on the east side of the head of West Salt Creek. He also recalled that a second precursor slide occurred on the west side of the creek later that morning.
■ Water in irrigation ditches originating in West Salt Creek stopped flowing. Hawkins said he went up the valley and heard trees snapping and toppling. That may have been due to mud/debris flow high on the valley floor.
■ That afternoon, Wes Hawkins, Melvin's son, and Clancy and Danny Nichols drove up the valley to assess damages to an irrigation diversion structure and whether there was a landslide risk to Salt Creek Road. Hawkins, 46, worked for the Collbran Conservancy District, and Clancy, 51, worked for Mesa County's Road and Bridge Department. Danny, 24 and Clancy's son, was a geologist with Olsson Associates in Grand Junction.
■ At 5:45 p.m, a magnitude 2.8 earthquake was recorded about eight miles southeast of Collbran, lasting for about three minutes, and reflecting the duration of the longest landslide in the recorded history in Colorado, at almost three miles in length. The landslide buried and killed Wes Hawkins and Clancy and Danny Nichols. It was caused by a rotational slide of a half-mile block in the Green River geological formation, with spring snowmelt and recent rain infiltrating rock joints, fractures and shear surfaces and likely triggering the slide. The rotational slide caused a rock avalanche and debris flow down the valley. Rock and debris moved fast enough to overtop two ridges where the valley curves, depositing rocks in some cases as large as small houses. The slide descended 2,100 feet and displaced an estimated 38 million cubic yards of earth, leaving deposits up to 123 feet on the valley floor and burying nearly a square mile of land. The slide encroached on a gas well pad but did not impact wells.
■ Melvin Hawkins reported hearing at that time what sounded like a long clap of thunder that rattled windows at his house. Another neighbor described what sounded like a low-flying, large military helicopter, while children reportedly spoke of hearing a noise like a freight train. There are no living eyewitnesses to the slide. The victims' remains and the vehicles they were driving never were found.
■ A week after the slide, as many as 1,000 people attended a service in Collbran to remember and honor the men who died. The service was briefly halted around 5:45 p.m. to mark the moment a week earlier when the slide occurred and took the lives of Wes Hawkins and Clancy and Danny Nichols.
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