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How are landslides classified by movement type?
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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 geology, landslides are primarily classified by their type of movement and the material involved (such as rock, debris, or earth). The five main categories of movement are defined as follows:
- Slides: These involve the displacement of material along one or more discrete shearing surfaces. They may be translational (moving along a planar surface) or rotational, which is known as a slump.1
- Flows: These are characterized by a distribution of particle velocities that resembles a viscous fluid. Water is typically the primary fluidizing agent.1
- Spreads: This is a complex lateral movement where relatively coherent materials rest on a weaker substrate that undergoes liquefaction or plastic flow.1
- Topples: This movement involves the rotation of a mass of rock, debris, or earth outward from a steep slope face.1
- Falls: These occur when materials detach from a steep slope and fall freely under gravity, often bouncing or rolling upon impact.1
Because these movements can be complex, a single landslide may exhibit more than one type of movement simultaneously.12