A natural arch is a natural formation (or landform) where a rock arch forms, with a natural passageway through underneath. Most natural arches form as a narrow ridge, walled by cliffs, become narrower from erosion, with a softer rock stratum under the cliff-forming stratum gradually eroding out until the rock shelters thus formed meet underneath the ridge, thus forming the arch. Natural arches commonly form where cliffs are subject to erosion from the sea, rivers or weathering (sub-aerial processes); the processes "find" weaknesses in rocks and work on them, making them bigger until they break through.
The Following is from Wikipedia.com's Natural Arch Page :
- Deep cracks penetrate into a sandstone layer.
- Erosion wears away exposed rock layers and enlarges the surface cracks, isolating narrow sandstone walls, or fins.
- Alternating frosts and thawing cause crumbling and flaking of the porous sandstone and eventually cut through some of the fins.
- The resulting holes become enlarged to arch proportions by rockfalls and weathering. Arches eventually collapse, leaving only buttresses that in time will erode.
This arch, Wilson Arch, is located on the side of the highway 191 on a beautiful sitting of colorful Entrada sandstone rounded cliffs. It is viewed by thousand drivers each day. A short trail allows you to climb up quickly and see the awesome work of nature.
Wilson Arch was named after Joe Wilson, a local pioneer who had a cabin nearby in Dry Valley.
Please do your best to calculate / guess the height and span of the arch and (optional) post a photo of you at the cache site with your GPS to your online log.