A rock shelter is a shallow cave-like opening at the base of a bluff or cliff. Another term is rockhouse.
Rock shelters form because a rock stratum such as sandstone that's resistant to erosion and weathering has formed a cliff or bluff, but a softer stratum, more subject to erosion and weathering, lies just below the resistant stratum, and thus undercuts the cliff.
This same phenomenon commonly occurs at waterfalls, and, indeed, many rock shelters are found under waterfalls.
Rock shelters are often important archeologically. Because rock shelters form natural shelters from the weather, primitive humans often used them as living-places, and left behind trash, tools, and other artifacts.
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