YELLOWSTONE NATIONAL PARK — The month of August marks the 65th anniversary of the magnitude 7.3 Hebgen Lake earthquake that occurred on Aug. 17, 1959 at 11:37 p.m., which caused a devastating landslide that killed 28 people and created the lake that is known today as “Quake Lake,” according to Yellowstone National Park (YNP).
At the time, it was the second-largest recorded earthquake in the continental United States during the 20th century. The earthquake was located just outside the western boundary of YNP, about 6.5 miles northwest of West Yellowstone, Montana.
“Although the initial event lasted only 30 to 40 seconds, the after-effects were catastrophic,” YNP said via Facebook. “Campers along the Madison River west of YNP awoke to a nightmare. Trees swayed and snapped as the earth shook. Then, a deafening roar filled the air as 80 million tons of dirt, rock and debris careened at 100 mph over their campsites and into Madison Canyon.”
According to the United States Geological Survey (USGS), the 28 fatalities were the result of the large landslide that was triggered in Madison Canyon. The landslide partially buried the Rock Creek campground on the valley floor, burying 19 campers. Others lost their lives to hurricane-force winds and a muddy wall of water exploding from the Madison River. The landslide dammed the Madison River, causing water to back up behind it, creating Earthquake Lake.
After the slide, officials rescued hundreds of people trapped in the canyon. Many rock slides blocked the roadways, and there was damage to the world famous Old Faithful Inn, where a large rock chimney collapsed. The state cleared debris and repaired damaged roads and bridges. The Hebgen Dam held and was repaired within several weeks.
The earthquake had a profound impact on Yellowstone’s thermal activity. USGS reported that at least 289 springs in the geyser basins of the Firehole River had erupted the day after the earthquake —160 were springs with no previous record of eruption. The earthquake was also responsible for the formation of Seismic Geyser, located in the Upper Geyser Basin. For several days after the earthquake, Sapphire Pool (located in Biscuit Basin) erupted about every 17 to 20 minutes to a height of three to six feet. Additionally, Old Faithful was observed to be more erratic than usual, with longer and shorter intervals between eruptions.
The effects of the quake can still be observed today. The fault scarp, which shifted the ground surface, ranges 18 to 20 feet and can be observed at the Cabin Creek Scarp Area and in Red Canyon.
Eight years after the earthquake, the U.S. Forest Service opened the Earthquake Lake Visitor Center, which is located on Highway 287, directly across from the original slide.
