Coming Down - Landslide EarthCache
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As an EarthCache, there is no 'container' to find, instead there is something interesting to learn about the geology of the area.
This Earth Cache is probably best done by safely parking well off the road on the EASTBOUND side of Highwat 82. There is plenty of room to safely park here. There is no need to cross the highway or stand near traffic while making the needed observations to complete this Earthcache.
This landslide area on the north side of the highway occurred over a period of months in 2011 and 2012, usually after heavy rains. The hill behind the slide area seen in front of you was about 100 feet high and sloped at 70 degree steep angle. This high angle was partly what casued the landslides to occur. The above soil and steep slope were removed as part of the strategy to prevent another landslide from occurring. The slope that did exit here rose was covered by just shallow rooted grass with no deep rooted trees. When the last landslide occurred it partially covered the northern most right lane on the westbound side of Highway 82. The slide area occurred along the entire horizontal length of the cleared area seen before you.
In order to log this Earth Cache, please email me the answers to following questions.
1. The bank that slid downward in the landslide is composed mostly of what two soil particles (check the soil particles behind you)? Do you think this contributed to landslide? Why?
3. How do you think heavy rains contributed to landslide occurrence?
4. Describe at least two methods that have been used to reduce the chance of a future landslide occurring and reaching the roadway again.
5. Do you think that the containment method is working and will it continure to work in the long term. Explain.
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A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows.
Landslides occur when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:
Groundwater (porewater) pressure acting to destabilize the slope
Loss or absence of vertical vegetative structure, soil nutrients, and soil structure (e.g. after a wildfire)
Erosion of the toe of a slope.
Weakening of a slope through saturation by snowmelt, glaciers melting, or heavy rains.
Earthquakes adding loads to barely stable slope.
Earthquake-caused liquefaction destabilizing slopes
volcanic eruptions.
Landslides are sometimes aggravated by human activities, Human causes include:
deforestation, cultivation and construction, which destabilize the already fragile slopes, vibrations from machinery or traffic, blasting, earthwork which alters the shape of a slope, or which imposes new loads on an existing slope, the removal of deep-rooted vegetation that binds colluvium to bedrock.
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