This massive Yellowstone earthquake destroyed a mountain and created a lake 190 feet deep
Dozens were killed, and a dam nearly gave way
Purley Bennett was camping with her family in West Yellowstone when she heard a great rumbling on the night of August 17, 1959. “I saw my husband yelling,” Bennett recalled. “He told me to grab a tree. I saw him grab a tree, but I never saw him again. I kept rolling over and over.” When Bennett awoke, she was pinned against a tree, her face bloodied and her clothes torn away by sliding rock. She was the only member of her family to survive — her husband and three children were among the 28 people to perish in the disaster that altered the landscape permanently.
With an epicenter in southwest Montana, the Hebgen Lake earthquake shook buildings in bordering Wyoming and Idaho. It was felt 350 miles away, and impacted water wells in Alaska and Hawaii. Pioneering seismologist Charles Richter remarked that the Lake Hebgen earthquake was “The largest so far as we know in the forty-eight states in the present century outside Nevada and California.” It was unfortunate timing that the tremor occurred in the middle of camping season, with hundreds of vacationers setting up tents in the trees along Hebgen Lake and the Madison River valley.
The 7.3–7.5 magnitude earthquake brought death in multiple forms, summoning the destructive powers of not only the earth, but of air and water. Some 180 million tons of mountainside tumbled into the valley at speeds of 100 miles per hour, creating hurricane force winds. Hebgen Lake shook so violently it almost breached its dam. But the night’s most lasting legacy comes in the form of Earthquake Lake, a six-mile-long, 190-foot-deep body of water created when the side of a mountain broke away and all but completely dammed the Madison River.
Jack Harris and Anita Epstein were scientists working in southwestern Montana for the United States Geological Survey at the time of the disaster. Like other geologists, they knew of the fault line that cut through their area but believed it to be inactive. Anita was shuffling cards when the lanterns in the house began to sway. Shelves rattled, and water splashed up from a washbasin. She hurried outside. “In the moonlight,” writes John McPhee in In Suspect Terrain, “she saw soil moving like ocean waves, and for all her professed terror she was collected enough to notice that waves were not propagating well and were cracking at their crests. She remembers something like thirty seconds of ‘tremendous explosive noise,’ an ‘amplified tornado.’”
The earthquake had a particular effect on Hebgen Lake, which had been created along the Madison River with the creation of the Hebgen Dam. As a relatively contained body of water, the tremor induced great waves to oscillate on its surface for 12 hours, in what is called a seiche, or the lake-bound equivalent of a tsunami. The earliest waves were most intense. They sent water beyond the shoreline and over the dam, cracking the concrete structure and even drowning people as they slept in bungalows.
The earthquake altered the artesian pressure in an already geyser-prone region, and spurts of water shot from the ground. The seismic event also wielded the atmosphere to devastating effect. Nearly half of a 7,600-foot tall mountain broke away, pushing vast pockets of air at hurricane speeds, which shifted cars and killed people as they were dashed against trees. Witnesses reported that when “the mountaintop crashed into the canyon there was a rush of air so strong it blew the clothes off of people.”
Aftershocks continued through the night, and everyone worried about Hebgen Dam collapsing. The town of Ennis, Montana, was evacuated, and through the early morning hours its residents were taken in by citizens of nearby Virginia City. “Everyone was wonderful,” one witness said. “We used station wagons as ambulances and started bringing the injured in. People gave away everything they had. When people came in without clothing, other people would give them what extra clothing they had. Several people were practically unclothed.”
Rescue efforts were stifled by the landslide, which had covered a half-mile stretch of highway. When day broke, smokejumpers — who traditionally parachute in to fight forest fires — descended on an area filled with trapped hotel guests, shelterless residents, and unfortunately, the dead. People cut through sagebrush so helicopters could land and airlift the injured.
Beyond immediate rescue, the Army Corps of Engineers mounted a massive recovery campaign to preserve the Hebgen Dam and ensure proper drainage for Earthquake Lake. Rebuilding the roads, covered by earth and torn by fissures, was a years-long project completed in 1963. Forest Service officials had commemorated the dead with a bronze memorial, and in 1967, they opened the Earthquake Lake Visitor Center to educate the public about the new terrain. Ten years after the earthquake, a New York Times reporter observed that “The lake seems eerie, what with its bone-white ghost trees, which were killed by the post-quake flooding.” Those trees still rise from the basin of the lake, and the site is replete with reminders of that disastrous night nearly 60 years ago, including mangled wood buildings along the shoreline, and swaths of earthen mountainside conspicuously bereft of pine and vegetation.
