Existing comment:
Ancient Sand Dunes:
This vast area was once covered by extensive sand dunes. Some 200 million years ago, winds from the northwest carried tons of fine-grained sand into this area, creating an immense desert.
Over time, the sand drifts were covered by other layers of sediment, compressed, and cemented by quartz and calcite into Navajo Sandstone.
Erosion has since washed away the overlying layers, exposing the "petrified" dunes. |