California Underground, Realms -- Wind & Rain


	Wind & Rain

	Weather carves away many kinds of rocks forming a variety of cave types. These caves are seldom big because the soft rocks collapse when cave chambers become too large.

	Wind, Step 1. Moisture persists on the shady side of a sandstone rock. Here it dissolves away the substances that glue together the rock's component sand grains.			Wind, Step 2. Loosened sand grains have blown away, leaving a shallow cave.>

	Rain, Step 1. Water percolates downward through soft sediments only to be stopped by resistant layers of sediment. Pressure builds up, causing water to flow out the cliff face, carrying sediment as it does.			Rain, Step 2. Over time the arroyo cuts deeper and the cliff face cuts back. The percolating water has excavated many soil-pipe caves deep into the sedimentary deposit.

	Rain and dew soaking into sandstone and similar rocks loosen mineral grains, which the wind blows away producing shallow wind caves. Man has frequently utilized these wind caves for storage or shelter. In even softer rock, groundwater erodes soft sediments and washes them out through hillside springs leaving small caves called soil pipes. Much like the formation of soil pipes, melt water coming off glaciers often leaves long glacier cave passages in the ice.

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