Yellowstone Was Rocked by a Magnitude 7.3 Earthquake 60 Years Ago—and the Scars Are Still Visible Today

Sixty years ago the Yellowstone region was rocked by a 7.3 magnitude earthquake which killed several people and left scars on the Earth that are still visible today.

The Hebgen Lake earthquake—as it is known—occurred on August 17, 1959 at 11:37 p.m. MST in Madison Canyon, just outside the western boundary of Yellowstone National Park. It lasted for about 40 seconds, with several strong aftershocks reported later.

Six decades later, it remains the largest earthquake ever recorded in the Rocky Mountains. In fact, it was one of the strongest ever recorded in North America, comparable in power to the devastating San Francisco earthquake of 1906.

"We often hear about the potential for large volcanic eruptions of the Yellowstone volcano in the news and on television shows," Jamie Farrell, assistant research professor at the University of Utah and Chief Seismologist of the Yellowstone Volcano Observatory, wrote in a blog post for the United States Geological Survey (USGS.)

"However, we rarely focus on the threat of large earthquakes in the region, even though the hazard and risk from these types of events is much larger than a volcanic eruption because they happen so much more frequently," Farrell wrote.

The quake led to the deaths of 28 individuals, the majority of whom were killed in a large landslide which sent 180 million tons of rock, mud and debris hurtling down into the Madison Canyon at speeds of around 100 miles per hour, producing hurricane-strength winds in the process, Timeline reported. This debris dammed the Madison River, leading to the formation of Earthquake Lake—which measures around six miles in length and extends to a depth of around 190 feet.

The quake also had several other notable impacts, in addition to the landslide. For example, the seismic tremors caused parts of the landscape to drop by as much as 20 feet, creating what are known as "fault scarps"—offsets in the ground where one side of a fault moves up or down in relation to the other side.

These scarps—which can still be seen today on the Hebgen Lake and Red Canyon faults—damaged highways, which along with landslide, trapped several tourists in Madison Canyon on the day of the quake.

The seismic shockwaves were so powerful that they produced large waves in Lake Hebden lasting for around 12 hours, which almost breached its dam several times. Known as "seiche waves," this phenomena occurs in enclosed or partially enclosed bodies of water.

The quake was felt as far as 350 miles away and caused rock slides in Yellowstone National Park. But perhaps its most intriguing effects were on the park's famous hydrothermal features.

"By the day after the earthquake, at least 289 springs in the geyser basins of the Firehole River had erupted as geysers; of these, 160 were springs with no previous record of eruption," Farrell wrote. "At least 590 springs had become turbid [cloudy or opaque.] During the first few days after the earthquake, most springs began to clear, but several years passed before clearing was generally complete."

"In addition, new hot ground soon developed in some places and this became more apparent by the following spring with the formation of new fractures. Some new fractures developed locally into fumaroles, and a few of these evolved into hot springs or geysers.

Farrell stresses that the area around Yellowstone—as well as large parts of the Western United States—is prone to earthquakes.

"Earthquakes happen nearly every day in the region, and occasionally the area produces strong earthquakes that are capable of affecting large areas and causing damage," he wrote. "We should expect similar effects if another earthquake of this size would to happen today, except there are many more people visiting the area today than there were in the summer of 1959. The more we are prepared for earthquakes, the better we will be after one happens."

Hebgen lake earthquake fault scarp
Hebgen Lake earthquake fault scarp in 1959. USGS photo by J. R. Stacy
Yellowstone Was Rocked by a Magnitude 7.3 Earthquake 60 Years Ago—and the Scars Are Still Visible Today | Tech & Science