Blue View - Earthquake Lake

On a Monday in August, the pleasant campground alongside the Madison River in southwestern Montana was full. If you’d arrived that afternoon looking for a campsite, you might’ve thought your luck was bad as you moved on to seek another place to pitch your tent, but it may have actually been the luckiest day of your life. At 11:37 that evening, an earthquake struck the area, causing a massive landslide that buried the campground, killing 19 people who were camped there.

This happened on August 17, 1959. The earthquake measured 7.5 on the Richter scale, which was, at the time, the second-largest earthquake ever recorded in the continental U.S. More than 80 million tons (!) of rock crashed down into the valley, totally damming the river. Just north of the epicenter was the Hebgen Dam, an earthen dam that was built in 1917. The north shore of Hebgen Reservoir dropped 19 feet, putting several cabins underwater, and the dam itself was damaged when waves caused by the quake swept over the top. The dam held, but the flash flood created by the waves killed another 5 people who had survived the landslide. In all, 28 people perished and approximately 200 others were either pulled from the river or were later rescued.

Hurricane force winds were created, overturning cars and knocking trees down. One camping trailer was missed by the landslide, only to be blown into the river. The couple inside managed to climb onto the roof as it floated down the river. When it began to sink, they were able to grab onto a tree branch, which they clung to throughout the night until they were rescued the following morning.

The drama didn’t stop there, however - the new, landslide-created, earth and rock dam had no spillway. In just a few weeks, the backed-up river would fill the newly created lake and begin to flow over the top of the dam. The water would erode the dam, allowing more water to flow out, causing further erosion… eventually leading to another flash flood downstream.

In one of the largest mobilizations ever undertaken in the U.S., the Army Corps of Engineers was immediately deployed, and in an amazing demonstration of logistics, ingenuity and heroics, managed to build a temporary spillway. Over the next two years, the Corps continued work on the two dams, repairing the Hebgen dam, and leveling and reinforcing the new dam. The newly formed lake, 5 miles long, a third of a mile wide and 190 feet deep, was appropriately named Earthquake Lake. It’s stocked with brown and cutthroat trout, and I’m told that the fly fishing is good.

We stopped there en route to Yellowstone. It was eerie seeing the partially submerged, dead trees that still stand near the shoreline, a grim reminder of the pleasant forest campground that once was. The campers that were buried by the landslide were never recovered and remain permanently entombed under the dam. The names of all 28 who perished are commemorated on a plaque that is mounted on one of the huge boulders that fell down into the river valley on  that fateful day.

Whew! I’ll try to find a less somber subject for next week’s Blue View. Stay tuned…