Initial Publication Date: June 17, 2005
The Hebgen Lake Earthquake Area, Montana and Wyoming
Route
Start point
No route givenEnd point
No route givenRoads (and Trails)
US 191, Montana 287Total distance
No route givenGeology
Summary
Several high-angle normal faults bounding the west front of the Madison Range north of Hebgen Lake, recurrently active during much of Neogene time, reactivated catastrophically on August 7, 1959. Faulting was accompanied by largest historic earthquake within the Intermountain Seismic Belt. Unusual geologic features were formed--spectacular fault scarps, a large landslide, a deformed lake basin (Hebgen Lake), and a new lake (Earthquake Lake)--each of which demonstrates the destructive power of a large eathquake. These features are described in the context of the bedrock geology in this field guide.Key Lithologic Features
- Precambrian gneiss, amphibolite, schist, and dolomite (part of the Cherry Creek metamorphic suite)
- landslide debris
Structures
- Red Canyon fault scarp
- Hebgen Fault scarp
- Madison Range fault scarp
- deformed Hebgen Lake basin
- Madison Slide
Landforms
- Madison Range
- fault scarps
- Hebgen Lake
- Earthquake Lake