Existing comment:
Rocks Become Rocks
Geologists group rocks into three basic types: igneous, metamorphic, and sedimentary. The rocks found in Arches National Parkare sedimentary. Simply put, sedimentary rocks are recycled rocks.
The Power of Water, Wind and Time:
The forces of erosion, chemical and mechanical weathering, wear away rocks, breaking them into smaller and smaller pieces, creating sediments. Water and wind carry the sediments downhill or downwind until they are deposited closer to the source and the smaller, lighter sediments are carried further.
Over long periods of time, sedimentary deposits can be overlain by more layers. As these upper, younger layers accumulate more and more sediment, their weight compacts older, lower layers. Minerals precipitated from groundwater cement the compacted sediments together, forming new rocks.
The rocks and landscapes of Arches today are the result of this process occurring for millions of years in a variety of past environments. The deposition of sediment has not been continuous. There have been long periods when no deposition occurred and periods when previously deposited sediments and sedimentary rocks were eroded away. These gaps, or uncomformities, reveal that nearly as much rock -- and therefore time -- is missing from the rock record as that which remains.
The rock column to your left illustrates the sedimentary rock layers that can be seen at Arches. |