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How can falling rock turn into a rock avalanche?

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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.

A rock avalanche is a specific type of avalanche that occurs when material on a slope breaks loose from its surroundings. While a simple falling rock is a localized event, it can evolve into a rock avalanche when a large segment of shattered rock is displaced and begins to move rapidly down a slope.1

As this mass descends, it quickly collects and carries additional material along with it, gaining momentum and volume as it travels. This process is a form of landslide characterized by the rapid, downslope movement of a large, fragmented rock mass.1