About 90 percent of rain and snow here is absorbed by plants or quickly evaporates, while only 10 percent of Pipe Spring’s precipitation soaks into the light-colored Navajo sandstone at the top of the cliffs, where water moves easily but slowly through the fine-grained rock. The red Kayenta mudstone in the cliff face blocks the water from going deeper into the earth. At the Sevier Fault, a fracture thousands of feet deep, rocks west of Pipe Spring have slipped down relative to rocks to the east, and water in the sandstone follows the slope of the land eastward. Groundwater creeps downhill until the impermeable Chinle mudstone formation at the Sevier Fault blocks it, then moves south in an underground trough formed where rock layers have bent along the fault line. At Winsor Castle, where the porous sandstone has eroded away, the water is released to the surface.