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What causes a sinkhole? A common misunderstanding is to think that a sinkhole is the hole in the rock. Actually, the sinkhole is what we see on the ground surface because of the hole in the rock below. The space in the rock (known as a void, solution cavity or cave) takes hundreds or thousands of years to form. Then, soil from above can move into the void in the rock. If the soil is sticky, a void can form within the soil. As more soil washes down (over years or maybe just days), the void space moves toward the surface until it can’t hold together anymore. When it collapses (or subsides), you see the sinkhole on the surface. Often, you can only see soil in the hole and not the actual hole in the rock itself because the rock is too far below. (www.depweb.state.pa.us)
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