Landslides In China, California, India... (part 2): Biggest Landslide Caught on Camera
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- ℹ️ Description
landslides are restricted to "the movement... of shear strain and displacement along one or several surfaces that are visible or may reasonably be inferred, or within a relatively narrow zone", i.e., the movement is localised to a single failure plane within the subsurface. He noted landslides can occur catastrophically, or that movement on the surface can be gradual and progressive. Falls (isolated blocks in free-fall), topples (material coming away by rotation from a vertical face), spreads (a form of subsidence), flows (fluidised material in motion), and creep (slow, distributed movement in the subsurface) are all explicitly excluded from the term landslide.
Under the scheme, landslides are sub-classified by the material that moves, and by the form of the plane or planes on which movement happens. The planes may be broadly parallel to the surface ("translational slides") or spoon-shaped ("rotational slides"). Material may be rock or regolith (loose material at the surface), with regolith subdivided into debris (coarse grains) and earth (fine grains).
Nevertheless, in broader usage, many of the categories that Varnes excluded are recognised as landslide types, as seen below. This leads to ambiguity in usage of the term.