In order to claim this Earthcache, please email me with the following:
1. Estimate how wide the denuded landscape is.
2. Based on your observations of the landslide, what type of earthquake do you think happened here?
3. Requested, but not required: take a picture of you and of those in your group with the fallen hillside behind you and post with your log.
You are free to log this as a find and I will notify you if there is an issue with your log and/or answer.
There are 3 main types of earthquakes. This lesson will teach you about those types of earthquakes and then lead into the earthquake that befell this region.
Strike-Slip Fault
In a strike-slip fault (also known as a wrench fault, tear fault or transcurrent fault), the fault surface (plane) is usually near vertical, and the footwall moves laterally either left or right with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults and those with right-lateral motion as dextral faults. Each is defined by the direction of movement of the ground as would be seen by an observer on the opposite side of the fault.
Dip-Slip Faults
Dip-slip faults can be either normal or reverse.
In a normal fault, the hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is a graben. An upthrown block between two normal faults dipping away from each other is a horst. Low-angle normal faults with regional tectonic significance may be designated detachment faults.
A reverse fault is the opposite of a normal fault—the hanging wall moves up relative to the footwall. Reverse faults indicate compressive shortening of the crust. The dip of a reverse fault is relatively steep, greater than 45°.
Oblique-Slip Fault
A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault. Nearly all faults have some component of both dip-slip and strike-slip; hence, defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, and others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active.
The hade angle is defined as the complement of the dip angle; it is the angle between the fault plane and a vertical plane that strikes parallel to the fault.
This location tells of the terror that befell the locals of the area and of people who were camping in the area. On August 17, 1959, there were multiple groups of people camping along the Madison River. They were suddenly awakened in the middle of the night by a loud noise that turned out to be the hillside above them crashing down after a 7.5 magnitude earthquake struck the area, causing an 80 million ton landslide. Upstream is the Hebgen Dam, with the Madison River flowing from it. The earthquake struck downriver from the dam and caused significant, but repairable, damage to the dam.
Due to the landslide, the Madison River began to backfill, and with no outlet for the water, Earthquake Lake was formed. Eventually the U.S. Army Corp of Engineers were brought in and created a spillway to minimize erosion and potential collapse of the natural dam.
According to the sign, 19 people were buried alive and their bodies were never recovered. Another 8 people were killed in the aftermath.
This location also gives you a great view of the fallen hillside ahead of you. It's amazing to me the lack of trees on that hillside, even this many years later.
The Earthquake Lake Visitor Center is just up the road and provides a panoramic view of the mountain that fell and of the lake.