Hazard Identification
 

What are landslides?

Landslides are mass movements of rock, debris, or earth down a slope (Huavin, et. al). They are caused by many external factors: (1) steepening the slope, (2) removing support from low on a slope, and (3) adding mass high on a slope. Earthquakes, volcanoes, wildfires, intense rainfall and floods, water-level changes, storm waves, or rapid stream erosion, all these event above can cause landslides. They are also caused by a internal factors: (1) inherently weak materials, (2) water in different roles, (3) decreasing cohesion and (4) adverse geologic structures. Combination of these events, such as by a heavy rainfall on a slope that has lost vegetation and groundcover due to a wildfire can also cause landslides. Landslides can affect all parts of society. They threaten highways, tourism, the fishing industry, mining, energy production, timber harvesting, and general transportation.

Some topographic features created by a landslide in it downward-and-outward movement (Abbott, 2006)

A hillslope may fail along an arcuate basal surface. The slope is in equilibrium when a driving mass portion is kept from the moving by a resisting mass portion. Adding to the  driving mass or removing from the resisting mass can cause landslide (Abbott, 2006).

A main view of the Guinsaugon landslide. Notice the stream channels on the landslide. The ground is over saturated. Intense rainfall weakens the clay minerals in the soil, liquefies the soil and other materials and causes the landslide.

A side view of the landslide. Sand, mud and boulder (bigger than human) are carried to the bottom of the mountain by the landslide.

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