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How do backward-tilted blocks form during a rotational slide?
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landslide
This 1995 landslide at La Conchita, a coastal town in California, swept away a hillside road and destroyed a number of houses.
In a rotational slide, also known as a slump, the movement of the displaced mass occurs along a concave-upward set of shear surfaces. As the mass moves downward along this curved slip surface, internal slip planes develop within the displaced material. Each of these internal planes causes the individual blocks of rock or debris to tilt backward.1
This back-tilting is a characteristic feature of the movement, often resulting in the upslope ponding of water, which can further enlarge the area of instability. The process continues until the slope is reduced to a very low gradient, at which point a stable condition is reached.1