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MAIN: ROCKS AND MINING: WATER RECYCLES ROCKS Water Recycles RocksWater creates, shapes, and destroys rocks as it cycles among land, sea, and air. When a river like the Mississippi dumps sediment into the sea, sand and clay settle in layers on the bottom, where they slowly turn into sandstone and shale. Meanwhile, the ocean water steadily evaporates into the atmosphere...then falls as rain or snow...which replenishes groundwater and the river...whose erosive energy carves away rock...creating new sediments that the river transports to the sea.....completing the cycle. A Subterranean Wonderland. Drop by drop, year after year, cave deposits slowly grow. Because these formations build up over many human lifetimes and are very fragile, they are irreplaceable. Today, both federal and state laws protect cave deposits. How to Make a Cave. Trickle rainwater through soil into cracks in a thick underground bed of limestone. The water will absorb carbon dioxide from the air and from microscopic organisms in the soil to become a weak acid. Let the acidic groundwater slowly dissolve calcite in the limestone. Tiny cracks will grow bigger as more rock is dissolved. The acidic groundwater that creates caves can also build wonderful cave formations. Loss of carbon dioxide from the water causes calcite to crystallize. |
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