August 18, 1959 Tsunami: Hegben Lake, Montana, United States
A tsunami caused by a magnitude 7.2 earthquake and a landslide began at Hegben Lake, Montana, United States on August 18, 1959 at 06:37:20 UTC. The water rose as high as 1 meters. Its effects were recorded at 1 place. It killed 28 people, counting the earthquake or eruption that caused it.
Where the waves reached
The source (white) and every runup with a place, colored by the water height recorded there. A ring is a runup NCEI marks doubtful.
- Under 1 m
- 1 to 3 m
- 3 to 10 m
- 10 to 30 m
- 30 m and more
- Height not recorded
The tsunami
- Date
- August 18, 1959, 06:37:20 UTC
- Source
- Hegben Lake, Montana, United States
- Cause
- Earthquake and landslide
- Earthquake
- Magnitude 7.2, 5 km deep
- Maximum water height
- 1 m (3.3 ft)
- Runups recorded
- 1
- Waters
- A lake or river, not the ocean
- How certain
- An event that only caused a seiche
- Source location
- 44.630° N, 110.891° W
The toll
- Deaths
- 28 with the earthquake or eruption that caused it
- Damage
- $11 million with the earthquake or eruption that caused it
- Houses damaged
- Some (about 51 to 100) with the earthquake or eruption that caused it
Where the literature gives no number, NCEI records a description on a scale of 1 to 4, printed here in its words. Damage is in millions of US dollars of the year of the event, not adjusted for inflation.
What the record says
NCEI’s account, from the sources it cites.
This earthquake was characterized by extensive fault scarps, subsidence and uplift, a massive landslide, and a seiche in Hebgen Lake. (reference #542)
The earthquake also caused a northward tilt of the Hebgen Lake bed. This triggered a reported 20-foot wall of water that overtopped Hebgen Dam followed by several 3-4 foot surges. (reference #12600)
"That one caused large waves in Hebgen Lake that went on for several hours and were more than 10 feet high, and overlapped Hebgen Dam several times," [Jim Pechmann, seismologist with the University of Utah] said. The waves started when the bottom of the lake suddenly tilted toward the fault. (reference #13787)
In addition, the sudden northward tilting of the basin caused Hebgen Lake to slosh back and forth. This is referred to a seiche wave. The waves were so large that they breached the Hebgen Lake dam a few times, leading panicked tourists to think the dam had failed. Luckily, the dam did not fail and the waves eventually died off. (reference #13788)
Reference #12345 lists this event as a validity 2 or questionable tsunami. (accessed April 2024)
Every runup
Nearest the source first. Heights are above sea level at the time; a tide gauge reads half the wave’s full height.
| Where | Country | Km from source | Water height, m | Inland, m | Measured by | First wave, UTC | Deaths |
|---|---|---|---|---|---|---|---|
| Earthquake Lake, MT, MT | United States | 47 | 1 | Other |
More
Every tsunami in 1959The 1900sTsunamis of United StatesThe earthquakeThis day in weather historyAlerts in force
Sources
Tsunami events and runups from NOAA’s National Centers for Environmental Information, Global Historical Hazard Database, cited as NCEI/WDS, doi:10.7289/V5PN93H7. Public domain. Read 2026-09-24. NCEI tsunami event 2371.