Quake

Hebgen Lake and the damaged and reinforced Hebgen Dam

It was Monday evening, August 17, 1959. I was 12 years old, ready to start Junior High in a few weeks. My parents owned a motel in Lewistown, Montana, and my brother and I had a wonderful large bedroom in the basement under the office. Even though it was not a school night, I was in bed and asleep. A 11:37 PM, I awoke to my bed shaking, and I was certain my brother had crawled across our bedroom and was shaking my bed to tease me. About the same time, my brother shouted out that I should stop shaking his bed. That’s when we realized it was an earthquake. We ran upstairs to my parent’s bedroom where my dad immediately accused us of shaking his bed.

Road washed out Hebgen Lake

There was none of the other signs of an earthquake. Nothing fell off the shelves, furniture didn’t tip over, and no sirens went off. Yet this was a 7.5 magnitude quake on the Richter Scale, and one of the most severe quakes ever recorded in the northern Rockies and the strongest in Montana recorded history. It was centered in the Madison River valley just northwest of the town of West Yellowstone and the west entrance to the great National Park.

Several hours later, around 3 or 4 AM, people started showing up at the motel looking for a room. They had been in lodging in and around Yellowstone Park, and the earthquake and aftershocks had them so worried that they drove several hundred miles north to get out of the region. I think they probably had driven until exhaustion before finding our little town and motel.

Dry Spillway Hebgen Dam

The earth shook, fell, and undulated across the greater Yellowstone area, into Wyoming and Idaho, and the effects were felt as far away as Seattle. The earthquake caused dramatic changes in and outside Yellowstone National Park. The quake caused new geysers to form, and from some hot springs muddy water flowed. One notable example was named Seismic Geyser, due to its origin. It started as a ground crack that formed during the quake that soon turned into a fumarole (steam vent) and over time, matured into a geyser.

An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. Earthquakes manifest themselves by shaking and sometimes displacement of the ground. Great plates in the Earth shift and move creating destructive vibrations as well as lifting and dropping large sections of land. These “tectonic” plates tend to move along preexisting breaks in the crust called “faults.”

My mom and my grandfather on damaged road

If you drive north out of West Yellowstone on state highway 191, a short ten miles out of West, you’ll come to an intersection and can turn west onto US 287. This highway takes you by the northern side of Hebgen Lake, a body of water formed by Hebgen Dam, which was built in 1914 at the entrance to the Madison Canyon. This was the center of the earthquake.

From there the Madison River, named by Lewis and Clark during their exploration of Montana, flows through the cannon and then north to near the town of Three Forks where it joins the Jefferson River and the Gallatin River to form the headwaters of the Missouri River. From there the Missouri flows north near Helena and through Great Falls where it turns east and flows out of Montana into North Dakota before turning south and eventually meeting the Mississippi in St. Louie.

Road along the lake showing high water mark from Quake Lake

The following Spring after the earthquake, my family drove down to reconnoiter the damage. The area was just recovering. Much of the road was temporary, gravel, and only one lane. We saw the devastation that comes when the Earth twists and shakes.

Now, some fifty-five years later, I recently revisited the site. The area around Hebgen Lake has been restored, and you can not tell anything happened except for some signs telling the tale. As you drive west, however, you soon encounter Quake Lake with its eerie submerged trees. Even after over 50 years, the land has barely healed. The side of the mountain where the slide came down is still naked and rough and giant boulders are strewn around in their final resting place after the '59 shaking. The slide itself looks like a great pile of gravel and earth and only now are small trees starting to take root.

Washed out and collapsed road

During the quake, the landscape surrounding the epicenter fell as much as 20 feet. Tsunami-like waves rose over Hebgen Lake lasting for twelve hours. And though the quake lasted less than a minute, with aftershocks continuing for some time, it took 28 lives and caused the equivalent of $75 million worth of damage in today’s dollars.

Slide

Hebgen Lake is used to store water from the drainage area at the headwaters of the Madison-Missouri river system. Hebgen Lake is about 15 miles long and on its southern end measures up to four miles at its widest point. A man-made lake retained by an earth-fill dam, Hebgen has been called the premier still-water fishing lake in Montana. The Hebgen Dam is a concrete-core earthen embankment dam 85 feet tall and 721 feet long.

Landslide from the distance

New fault scarps as high as 20 feet formed near Hebgen Lake. (A fault scarp is a step like area on the ground surface where one side of a fault has moved vertically with respect to another.) The major fault scarps formed along pre-existing normal faults northeast of Hebgen Lake.

Subsidence occurred over much of an area that was about 15 miles north-south and about twice as long east-west. As a result of the faulting near Hebgen Lake, the bedrock beneath the lake was permanently warped, causing the lake floor to tilt and generate a seiche. Maximum subsidence was 22 feet in Hebgen Lake Basin. About 80 square miles subsided more than 10 feet, and about 300 square miles subsided more than 1 foot. The earth-fill dam sustained significant cracks in its concrete core and spillway, but it continued to be an effective structure.

Landslide

At Hebgen Lake itself considerable damage was caused by waves generated by the quake. These waves, known as seiche, differ from tsunami waves because in a seiche the entire water within a lake continues to slosh back and forth as the earthquake distorts the lake bed. Cabins along the lake shore were lifted off their foundations by the waves and were dumped when the waves receded. The dam itself, though damaged, held, although it was a point of great concern in the first hours after the quake.

Landslide

Much greater damage and loss of life occurred near the west end of the Madison canyon where a great landslide dammed the Madison River creating Quake Lake, a body of water 6 miles long and 200 feet deep. The landslides caused by the quake carried 80 million tons (40 million cubic yards) of rock, mud and debris down into the valley and created hurricane force winds strong enough to toss cars. In Madison Canyon, a family of seven were swept away by the landslide, five of whom perished. Two more fatalities were also reported in nearby Cliff Lake to the south. In Rock Creek, tourists camping there were caught off guard by the quake and landslide, which swept them into the creek.

The landslide caused by the quake blocked the flow of the Madison River. The blockage caused the water to rise and formed a new lake, which was later to be named Quake Lake. Fearing that the pressure caused by the rising water would result in a catastrophic flood, the Army Corps of Engineers began to cut a 250 ft wide and 14 ft deep channel into the slide. By September 10, water began to flow through the channel. To prevent more erosion by the flowing water, the Army Corps cut another 50 ft channel which was completed on October 29.

Boulder that rolled across canyon photographed in 1960

Imagine yourself, camping outside Yellowstone Park, in 1959. Perhaps the park campgrounds were full, or you were camped near the lake for the excellent fishing, or perhaps you had started your journey home after a pleasant visit to the park.

Even though it was a Monday, the eight official campsites at Rock Creek Campground filled early the afternoon of August 17. By evening those who arrived had to settle for “unofficial” sites further up or downriver. Still, the mood was cheerful — it was a beautiful moonlit night.

Same boulder photographed in 2014

At 11:37 PM, the shaking began. Some thought it was marauding bears, but those that looked outside realized something bigger was going on. Trees swayed and cracked, rocks jumped into the air. Loose boulders began to bounce down from above. A few minutes later, came a hellish roar. For those camped closest to the canyon mouth, it was the last sound they ever heard as millions of tons of rocks and debris smashed across their campsites. Just upstream, the roar was accompanied by a hurricane-force wind and a wall of muddy water that swept away vehicles, tents, and people. Nineteen people were buried outright by the slide, their bodies never found. A total of twenty-eight people died as a result of the earthquake. More than two hundred others were eventually rescued. The campers had been savaged by three separate dramatic events: first, the largest earthquake in the Rocky Mountains; shortly after that, an 80-million-ton landslide; and then the rising water.

Landslide 2014

Imagine being trapped here in Madison River Canyon on the night of the earthquake. Dust chokes the air. Aftershocks rattle the ground, and you can hear the crash of boulders as they fall from cliffs above and smash through the forest. To make matters worse, there’s a dam upstream, and it could burst at any moment.

Landslide 2014

That’s the nightmare that faced the survivors of the earthquake. Seeking high ground, drawn by headlights and firelight, many of the refugees converged at what is now called “Refuge Point” — where they found help, comfort, and hope.

After the quake settled down, the dazed campers and others trapped in the canyon began to gather. By 1 am, the first groups had made their way to Refuge Point. They compared experiences: “The highway’s washed out above the dam” … “There’s a mountain of rocks blocking escape to the west” … “The Madison is flooding — I heard people screaming for help” … Carload after carload of frightened and injured people continued to arrive as a thunderstorm rolled above.

Hill side where slide originated 2014

This is the nightmare that faced some 250 women, men, and children in the aftermath of the earthquake. Drawn to the higher ground by headlights and firelight, many of the shaken refugees converged on a small ridge, offering one another companionship and a greater feeling of safety — while they waited for dawn to break and for news from the outside world.

Around noon on the day after the earthquake, a DC-2 carrying Forest Service smokejumpers flew in through the west end of Madison Canyon. People on the ground felt relief and gratitude as they watched the unfurling of orange and white parachutes. The smokejumpers brought rescue gear and hope. For the next several days the smokejumpers worked with the Highway Patrol and other Forest Service rescuers. After helping people evacuate at Refuge Point and the dam, some stayed on for search and rescue efforts at campsites down the canyon, where Earthquake Lake was on the rise.

Hillside 2014

The colossal landslide across Madison Canyon created a rock dam across the Madison River, blocking the river’s swift current. By dawn the next day, a brand-new lake, churning with muddy water and strewn with broken trees, and risen to engulf the campground near the slide.

Over the following weeks, the water rose nine feet per day as increased stream flow (probably triggered by the earthquake) poured down the Madison. Within three weeks the lake was five miles long and had reached a maximum of 190 feet deep. Only the brushy tops of the drowned trees remained to show where forest once covered the canyon floor.

The rapidly rising lake posed an increasing threat: would the water burst through the slide dam and flood the Madison Valley? Engineers constructed a spillway through the slide to relieve some of the pressure and control the flow.

Dead trees in Quake Lake 2014

Since the spillway construction in September 1959 the Madison River has gradually worn the channel across the slide deeper, and the lake level has dropped. The result? A “bathtub ring” of dead trees around the lake’s margin marks the former level of Earthquake Lake. The upper edge of this ring marks the lake’s highest point before the water began to drop. Eventually, as the spillway further erodes, the lake will “drain” and the river will resume its path.

Dead trees in Quake Lake 2014

With the silver-gray tree trunks rising from its waters like dry bones, Earthquake Lake is uncanny-looking. The eerie trees are clues to the lake’s strange and abrupt formation, which began on that night in 1959. In the early morning, when mist rises from the water, the skeletal trees that loom from Earthquake Lake appear ghostly. They’re just a hint of the strange world below, where scattered relics along the lake bottom tell a story of terror and loss: picnic tables, crushed cars, toys, fishing gear … all abandoned during a few tragic hours in August so long ago.

Sign showing original landslide magnitude and Quake Lake

Now, in the mixture of natural beauty, the blue of Hebgen Lake, the green of the surrounding hills, the many cabins and fishing huts that dot the shore are testament to a return to normalcy. It is good to enjoy the beautiful mountains, valleys, and rivers that run through them. But it is also good to remember the powerful forces that built these geological structures. Sometimes nature will display this power without a warning.

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