Calcium carbonate is readily dissolved by rain or flowing water. Here, water sitting in a depression in the rock surface gradually dissolves the calcite cement that binds the sand-sized rock grains together. When the water is gone, wind blows the grains away, enlarging and deepening the depression, allowing more water to collect. As this cycle repeats, the depression gets larger and larger. Such depressions are called 'tenajas'.

© 2001
Photo by David J. Leveson