1959 Yellowstone earthquake

The 1959 Yellowstone earthquake¹ also known as the Hebgen Lake earthquake¹ was a powerful earthquake that occurred on August 17, 1959¹ at 11:37 pm (MST)² in southwestern Montana. The earthquake was registered at magnitude 7.3 – 7.5³ on the Richter scale.⁴ The quake caused a huge landslide that caused over 28 fatalities and left $11 million (1959 USD, $74.1 million 2006 USD) in damage. The quake induced landslide also blocked the flow of the Madison River resulting in the creation of Quake Lake. Effects of the earthquake were also felt in Idaho and Wyoming.⁵

The 1959 quake was the strongest and deadliest earthquake to hit Montana since the 1935-36 Helena earthquakes left 4 people dead and caused the worst landslides in the history of the Northwestern United States since 1927.⁵

Location

The quake struck in Madison Canyon, an area in Yellowstone National Park that at the time of the quake was geologically active.⁵ In addition, several nearby campgrounds were filling up with campers and tourists before the quake struck.⁵

The Earthquake

The earthquake began at 11:37 p.m. (mst) with the epicenter registered between 7.3 and 7.5 on the Richter scale.³ The U.S. Weather Bureau reported that the quake lasted 30-40 seconds.⁶ During the earthquake the surrounding landscape dropped as much as 20 feet (6 m) and shockwaves caused numerous tsunamis to surge across Hebgen Lake for 12 hours. Water pushed by the tsunamis poured over the dam which did not collapse.¹ Several aftershocks ranging from 5.8 to 6.3 were reported after the quake.²

Impact

The landslides caused by the quake carried 80 million tons (40 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 by causing a tsunami which inundated trailers and tents, uprooted trees, and injured one additional person.⁵

In Yellowstone Park near Old Faithful, the earthquake damaged the Old Faithful Inn, forcing guests there to evacuate. Landslides caused by the quake blocked a road between Mammoth and Old Faithful, damaging a bridge inside the park.⁶ There was one reported injury when a woman broke her wrist in the quake.⁷ The earthquake also created fault scarps as high as six meters, causing extensive damage to roads, homes and buildings.⁴ In Belgrade, the earthquake damaged measuring equipment placed in a 100-foot (30 m) water well.⁶ The quake also knocked out telephone communications between Bozeman and Yellowstone, with the City of Bozeman itself suffering moderate quake damage to homes and buildings.⁸ Buildings at the Montana State College campus also sustained quake damage.⁵ In Butte, the quake caused a pendulum clock to stop at 12:42 a.m. (MST) and caused minor damage to homes.⁹

Areas around Hebgen Lake were also hard hit as the quake caused parts of the lake to rise eight feet. Roads and highways running along coastal sections of the lake collapsed into the water.⁵ In Ennis, majority of the residents there evacuated due to the threat that water from Hebgen Lake might flood the town. The evacuation was called off when the landslide blocked the river preventing the water from flowing.¹⁰ In West Yellowstone, the earthquake damaged a courthouse⁶ and a railroad station.¹¹

The earthquake also caused damage and fatalities outside of Montana. In Renyolds Pass in Eastern Idaho, a landslide killed eight more people.⁷ Seismic waves from the quake were reported in Boise and Macks Inn. The quake there caused minor well and sewer damage. In Salt Lake County, Utah, police officers at the local jail and officials at the Salt Lake Municipal Airport felt the effects of the earthquake. Residents in Utah also felt the quake. In Needles, California the seismic waves caused by the quake triggered mudslides that buried US highways 66 and 95 trapping motorists and leaving the town without radio communication.¹¹ Seismographs in New Zealand⁵, British Columbia and the Dakotas¹¹ recorded the effects of the earthquake. In Puerto Rico, the distant effects of the earthquake caused water in wells to drop .01 ft (.003 meters).⁵ The final death toll from the earthquake was 28 ⁴ although some newspaper reports suggested the death toll is high as 50-60.⁷ and $11 million (1959 USD, $74.1 million 2006 USD) in damage.⁴

Aftermath

A radio operator of K71CM broadcast news of the quake at 11:43 p.m. (MST). At 11:50 p.m., another radio operator in Idaho contacted the Idaho State Police who in turn contacted their headquarters in Boise. The Montana Highway Patrol, Montana State Civil Defense and the Montana Fish and Game Department also received word of the earthquake and its effects. The geography of the area plus the damage from the earthquake disrupted and/or obstructed radio communications, making broadcasting accurate information about the quakes effects difficult.⁵

The American Red Cross, The Yellowstone County Chapter, Salvation Army and various other states, local and national organisations sent aid to the victims of the earthquake. The Red Cross also set up temporary housing in Bozeman and the Wyoming Health Department sent 200 trailers to the Yellowstone area to be used as hospitals.⁶ Because the majority of the roads in and around the Yellowstone area were either damaged or blocked by the landslides and the quake, equipment and personnel from the United States Airforce and the U.S. Forest Service were brought in to transport the injured to nearby hospitals outside the quake zone and to perform search and rescue missions in Madison Canyon. 300 people trapped in the canyon were rescued.⁵ Rescuers found five⁵ to nine bodies in the earthquake zone.⁶ Residents from the town of Ennis were evacuated to Virginia City⁸and Butte.⁹

Senators and Representatives Frank Moss (D-Utah), John Baldwin (R-California), Harold Johnson (D-California), Lee Metcalf (D-Montana), Leroy Anderson (D-Montana), Tom Morris (D-New Mexico) and Gracie Pfost (D-Idaho) overflew and surveyed the disaster area.⁶ The Senate Interior and Insular Affairs Committee requested Montana Governor J. Hugo Aronson to declare the areas hardest hit by the quake a disaster area.⁷ Wyoming Governor Joe Hickley provided help and equipment in the aftermath of the quake.⁸ The Montana National Guard was called to the quake area to prevent looting of campsites left abandoned by the quake.⁹The Idaho National Guard were also sent to the quake area.¹¹ The Montana Highway Department began clearing roads of debris and mud.⁵ The work was slowed by aftershocks and smaller landslides.⁶ On August 19, US Highway 20 and US Highway 191 were reopened while Montana State Highway 1 remained closed. Three bridges in Duck Creek, Cougar Creek and Madison Canyon were repaired and reopened as well. Because of the threat of gasoline spilling into a Missouri and Three Forks River, the a local pipeline company built an emergency pumping station⁸ The Montana Power Company surveyed Hegben Dam and found it sustained minimal damage.⁸ The Hegben Lake was complelty drained for crewmen to make repairs and to rid of dead or dying fish. Overall repairs to the Yellowstone National Park amounted to $2.6 million (1959 USD).⁵

50 people including police officers, members of the Red Cross and others held a memorial service a mile north of the slide in Madison Canyon for campers presumed buried under the quake induced landslide. The services lasted for 15 minutes.⁶After the quake, the U.S. Forest Service built the Quake Lake visitor center on top of the landslide¹ which was completed in 1967.¹² The U.S. Forest Service placed a plaque on one of the boulders that fell during the quake to honor the 19-21 people who were killed during the quake induced landslide.⁵

Formation of Quake Lake

The landslide caused by the quake blocked the flow of the Madison River.⁴ The blockage caused the water to rise and new lake (which later to be named Quake Lake) to form. 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 (76.2 m) wide and 14 ft (4.3 m) 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 (15 m) (15.2 m) channel which was completed on October 29. The construction of the two channels amounted up to $1.7 million (1959 USD).⁵

Records

The magnitude of the 1959 earthquake varies; the United States Geological Survey recorded the quake at 7.3⁴ and 7.5 on the Richter scale.³ other seismographs recorded the quake registering at 7.8. Because of this, the 1959 earthquake is compared with the 1906 San Francisco earthquake as one of the strongest earthquakes in North America,⁵ behind the 1964 magnitude 9.2 Good Friday earthquake in Alaska. The 1959 earthquake is also the most severe earthquake in the Rocky Mountain area of the United States along with the 7.3 magnitude earthquake which struck Idaho in 1983.¹³ The landslide caused by quake was the largest since an earthquake in Wyoming in 1925 caused a landslide amounting to 50,000,000 cubic yards (38,000,000 m³) of rock and debris that left 70 people dead. The death toll from the quake was also the highest since the 1925 earthquake and most recent for the Northwestern United States since an earthquake in 1927 that left seven people dead. The 1959 earthquake was also the most damaging earthquake to occur in Montana since the 1935-36 earthquakes that left four people dead.⁵ The Hebgen Lake area also experienced earthquakes again in 1964, 1974, 1977 and 1985.¹³

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