In Desert Environments Giant Sand Dunes Can Harden into Solid Rock
"This formation is composed of ancient sand dunes, produced when winds,
blowing across an ancient desert, piled up grains of sand. Over time, the dunes
shifted and were reworked. Eventually calcium-bearing solutions cemented them
in place. The resulting formation seen in this Navajo sandstone is called "cross-bedding".
The frozen dunes reveal that the wind direction was from north to south (from
left to right, in the photo). The "checkers" that groove the surface of this
formation are formed by the weathering of horizontal bedding planes and vertical
cracks." 1
Photo is Courtesy National Oceanic and Atmospheric Administration.
Cross-bedding is an eolian feature commonly seen in rocks formed by lithified
wind-blown deposits. How long does it take for loose particles of sand to become
solid rock?
It would take millions of years to compact and lithify huge sand dunes.
