Hebgen Lake Landslide - PowerPoint PPT Presentation

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Hebgen Lake Landslide

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Extensive fault scarps, subsidence and uplift, a massive land, and a seiche ... Cascaded from the steep south wall of the Madison River Canyon ... – PowerPoint PPT presentation

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Title: Hebgen Lake Landslide


1
Hebgen Lake Landslide
2
1959 Yellowstone Earthquake
  • August 17, 1959 _at_ 1137 in Southwestern Montana
  • Strongest and deadliest earthquake to hit Montana
    since 1935

3
Epicenter
  • Epicenter was located just outside of Yellowstone
  • 7.5 Magnitude
  • Earthquake was felt in 9 states and aftershocks
    were felt for several months after.

4
The Earthquake
  • Extensive fault scarps, subsidence and uplift, a
    massive landslide, and a seiche in Hebgen Lake.
  • A maximum MM intensity X was assigned to the
    fault scarps in the epicentral area.
  • Area of perceptibility, maximum intensity, and
    Richter magnitude all were larger for this
    earthquake than for any earlier earthquake on
    record in Montana (from May 1869).

5
The Slide
  • The largest effect that caused the most disaster
    was the huge avalanche of rock, soil and trees.
  • Cascaded from the steep south wall of the Madison
    River Canyon
  • 2,000 ft. long, 1,300 ft. wide ridge section

6
Creation of the Lake
  • The slide formed a natural dam that blocked the
    gorge and stopped the flow of the Madison River.
  • Volume of material that blocked the river below
    Hebgen Dam was around 28-33 million cubic meters.
  • Within a few weeks, a lake was created almost 53
    meters deep.
  • Earthquake Lake - reached back many miles toward
    Hebgen Lake.

7
Damages
  • 28 total deaths (most of which were caused by
    rockslides that covered the Rock Creek public
    campground on the madison river, about 9.5
    kilometers below Hebgen Dam).
  • 11 million in damages
  • Numerous roads and building structures were ruined

8
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