Friday, August 16, 2013

The Mighty Cliffs of Zion

Zion National Park is a magnificent show of the layers of sandstone making up the vast Colorado Plateau. The Navajo sandstone cliffs in the background are believed to be the tallest sandstone cliffs in the world. The bottom-most layer visible in this picture is the Moenkopi Formation that composes the rocky slopes The lower red cliffs are the Moenave Formation, deposited in streams and ponds. There is a narrow Kayenta Formation just below the vast smooth cliffs of the Navajo sandstone. The National Park Service describes the forces that made Zion as it looks today as follows:
Zion was a relatively flat basin near sea level 240 million years ago. As sands, gravels, and muds eroded from surrounding mountains, streams carried these materials into the basin and deposited them in layers. The sheer weight of these accumulated layers caused the basin to sink, so that the top surface always remained near sea level. As the land rose and fell and as the climate changed, the depositional environment fluctuated from shallow seas to coastal plains to a desert of massive windblown sand. This process of sedimentation continued until over 10,000 feet of material accumulated.

No comments:

Post a Comment