On August 17, 1959 at 11:37pm, one of the largest earthquakes recorded in North America shook the area of West Yellowstone. The earthquake caused a gigantic tital wave that rushed over the dam and into the narrow valley below. This 20 ft high wall of water travelled down Madison Canyon which was full of campers and vacationers. Further down the valley, half of a 7'600ft mountain fell into the valley (44 million cubic yards of solid rock). House size boulders rolled into the campground. The rock avalanche created hurricane force wind to move up the narrow valley blowing away trees and vehicles. The avalanche also damned the river creating a new lake, earthquake lake. Twenty eight people were killed. The earthquake was a 7.8 magnitude and was recorded by seismographs as far away as Hawaii!
It has to give sometime. The internal forces of the Earth create great stresses that build up for years or even centuries. When the stress is released it creates the great shaking kown as an earthquake. Geologists call the West Yellowstone earthquake a classic textbook earthquake becuase it had all the classic actions that an quake is likely to cause - siches (large waves), fault scarps, tilting, sink holes, displacements, and landslides. The quake created three major faults and displaced Red Creek as much as 20 feet. Thermal features in Yellowstone were altered due to the quake.
The site of the huge landslide had a unique structure. A nearly verticle layer of dolomite rock (relatively strong) supported the large mounatin of mostly shcist (not very strong). The earthqake fractured the dolomite buttress allowing the mass amount of rock to surge into the valley. All of this happened in just a few seconds. It took eight seconds for the 80 million tons of rock and timber to travel 1,200 feet into the valley below. As the mass reached the valley floor it was travelling 174 miles per hour. It took only 30 seconds for the mass to travel half a mile across the valley and three quarters of a mile up and down the valley. The landslide damned the river creating a new lake - Earthquake Lake. The landslide was respnsible for most of the deaths. All of the people that were buried in the landslide still remain there, the number of deaths will never be known for certain.
What to do
The West Yellowstone Earthquake area is located northwest of the west entrance of Yellowstone National Park on highway 287. As you drive through the area there are multiple signs and stops to observe (this being one of them) the aftermath of the earthquake. Along the drive you can see the huge fault scarp, cabins that sunk into the lake, Earthquake Lake with trees sticking out of the water, and of course, the huge landslide. There is a visitor's Center built on top of the landslide that is worth visiting.
Lake Hebgen, MT
To log this earthcache:
Go to the posted coords, take an OPTIONAL photo of you and your group.
Tell us some of the effects of the earthquake of 1959 that are listed on the sign that is located on the back side of the restroom of this public park AND/OR Research or visit other locations and tell us some of the effects of the earthquake of 1959.
Updated logging requirements as of Sept 15th, 2013 to make it a little more understandable...and please DO NOT post your answers with your log. Once you email the answers feel free to log your find online. I do not respond unless there is a problem with your answers.
Find more infomation about the earthquake at this link.