A night of tremors, terror

2009-08-16T00:30:00Z A night of tremors, terrorMARY PICKETT Of The Gazette Staff The Billings Gazette
August 16, 2009 12:30 am  • 

Fifty years ago Monday, a massive earthquake near Hebgen Lake rumbled through a peaceful mountain night, changing the Madison Canyon forever.

The chain of events began at 11:37 p.m. Aug. 17, 1959, when two blocks of the Earth's crust north of Hebgen Lake dropped over existing faults, setting off an earthquake measuring 7.5 on the Richter scale.

Waves on the waters

The drop caused Hebgen Lake's north shore to tilt downward, sending lakeside cabins into the water and flooding parts of Highway 287. It raised the south shore so much that docks once lapped by water stretched across dry beach.

Tidal waves of water sloshed across the lake and crested Hebgen Dam. Although the quake cracked the dam, it didn't give way as some feared it might.

The most dramatic event unleashed by the quake was several miles to the west near the narrow mouth of Madison Canyon.

The quake cracked dolomite underpinnings of an unnamed mountain, sending 80 million tons of rock rushing down over the river and the west end of a campground and partway up the other side of the canyon, damming the Madison River.

So much rock fell in a few seconds that it created near-hurricane force winds that would kill and injure several people and beat camp trailers and cars into twisted wreckage.

The survivors soon were confronted with rising water as the river began backing up against the landslide.

Cut off

Those trying to flee in their cars found their way blocked by a highway that disappeared into floodwaters or dropped off over broken pavement.

Nineteen people were thought to have been buried at the undeveloped western end of the Rock Creek campground. It would take weeks to piece together stories from families of missing vacationers to indicate that they were probably caught in the slide.

The developed part of the campground now lies under Earthquake Lake, formed when the Madison River backed up behind the slide.

At the Cliff Lake campground west of Hebgen Lake, a man and his wife were crushed to death by a large boulder that crashed down them where they slept. The boulder missed the man's three sons sleeping nearby and a picnic table full of food.

Five more bodies - four from a single family - were found near the slide. Two people who initially survived later died at a Bozeman hospital.

Through the long night and into the next day, survivors were cut off from the outside world.

Fear of flooding

Worried that the quake might have damaged Hebgen Dam and could flood Ennis downstream, authorities evacuated the town.

The quake, with its epicenter about 9 miles north of Hebgen Lake, was felt as far away as Seattle and caused damage in West Yellowstone, Ennis and Virginia City.

In Bozeman, bricks shook loose from Montana Hall on the Montana State College campus and chimney tops of homes along South Willson Avenue.

In Yellowstone National Park, the quake collapsed a fireplace and chimney at Old Faithful Inn, sent rock slides across several roads and altered hot springs and geysers. After the quake, the average interval between eruptions of Old Faithful increased by a few minutes.

To prevent water backing up behind the slide in the newly named Earthquake Lake from eroding the natural dam and flooding Ennis, a channel was cut through the slide to start the Madison River flowing again.

Victims remembered

A year after the quake, a memorial was dedicated to the people who died there. Several families are on the list. They include Bernie and Inez Boynton and Margaret Holmes, all of Billings.

The memorial plaque with the names of the dead is attached to a giant boulder that moved on top of the slide down from the mountain and across the river valley.

A visitor center was built with a view looking out onto the scooped-out hollow where the face of the mountain collapsed 50 years ago.

Joanne Girvin, visitor information assistant at the visitor center, likens the slide to the mountain losing its belly, leaving a concave, irregular, gray and reddish cirque.

The rubble across the slide's pathway remains nearly as raw as the day the dust cleared. Only a few trees have grown up on its rocky face.

Contact Mary Pickett at mpickett@billingsgazette.com or 657-1262.

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