Geologists frequently visit damaging landslides to learn what caused them and ho

Question

Geologists frequently visit damaging landslides to learn what caused them and how they might have been prevented. Such information can be valuable in liability lawsuits and to avoid future disasters. The key to this work is an understanding of landslide triggers. You have been hired to investigate how human versus physical actions could trigger landslides. To complete your study, you must use the link on the left to:

1.Clearly understand the natural and human actions that can trigger landslides.

2.Use your new knowledge to diagnose six landslides on different landscapes to determine their triggers.

Part A

Illustrations of six landslide sites are shown below. You can access larger versions of these sites by clicking on the link on the left—Sites to Evaluate.

Each of the six sites shows the bottom (slip) surface of a landslide with a dashed black line and the direction of landslide movement with a solid black line and arrow above the dashed black line.

In each scenario, determine whether the landslide is caused by natural forces or human action. For all sites, pay close attention to the location of the arrows to determine what triggered the landslide.

NOTE: The gray layer in Sites 2 and 5 is fill dirt added to the landscape to level the otherwise steep topography.

Hint 1. What the landscapes depict—human versus natural occurrences

Look at the six different landscapes again and determine the human and natural processes occurring. Ask yourself whether natural occurrences such as forest fires, earthquakes, rainfall/snow, or rivers are evident. If most of these phenomena/processes are evident, then the majority of the landslides shown will be nature induced. Otherwise, the presence of human settlement evident by the buildings will make human influence more prominent in these landscapes.

Hint 2. How human construction and removal of support are related to landslides

Human activities such as building a house or excavating at the base or along a slope may affect the topography of an area. This could cause the slope to exceed the angle of repose and induce a landslide.

Hint 3. How water bodies and erosion are related to landslides

Erosion at the base of a slope by a stream is a natural process that has the potential to remove support and initiate a landslide.

Explanation / Answer

Site 1, 2 and 3 are natural triggers because seeing the point where landslide is happening is not close to the human settlement which means that the landslide is cause by natural triggers.

Site 4, 5 and 6 are man made triggers because the point of landslide coincides with human settlement, and the reason of landslide could be excavation in order to set up the base which resulted in losening the soil and ultimately causing landslide.

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