There is some landslide terminology you should know about. Figure 56 shows a few of the features you might see after one has happened. They are labeled from "head" to "toe", so to speak. Crown cracks are seen above the landfall where the earth has been tugged by the weight of the fall before it fell. The crown is the top of the earth just above the landslide. A scarp is a cliff face; there can be a main scarp and one or more minor scarps. At the top of a minor scarp is a ledge called a head. The upper part of the fall is the zone of depletion, where rock has been removed from a spot. The bottom part is the zone of accumulation, where rock or debris has been added. You will be able to see the surface of the rupture and its main body, where the debris is missing. More debris is added to existing debris at the foot of the landfall. The very ends of the landfall you see after it has traveled are the tips of the toes, but the toes themselves are the bottom edge of the rupture itself. The surface of separation is below the rupture. Expect to see some transverse cracks from side to side as well as radial cracks that run up and down along the zone of accumulation. In between cracks, you can have buildup that forms ridges of debris near the base of the landfall.
TYPES OF LANDSLIDES Most landslides happen in more remote areas where people are not significantly affected. Landslides are not all dramatic and catastrophic. You can have various types of rapid or slow mass movement of earth. The material that falls and the mode of falling both go into the classification of a landslide. These include the following different types of phenomena: •
Slides or sliding events – these are true landslides in restrictive sense. There is usually a single weak point or weak zone that causes a separation of earth from its original elevation. Rotational slides involve a concave slope left over after the slide has happened. There is a greater slope at the top of the slide than the bottom. A translational slide is simpler, with just a fall down an inclined plane. Of
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