Rock Decay

Rock decay is the principle mechanism which has shaped the present day configuration of Valley of Fire park. Without weathering, rocks would maintain their original appearance and location without any natural weathering processes to act upon them. Independent jointing in sandstone offers some of the first opportunity for infiltration by the forces of nature. As the exterior becomes vulnerable to water the process can begin. As water penetrates into the sandstone, the initial faults become more pronounced. Repeated freezing and thawing in these crevasses pushes the rock further apart.

A photo I took at the park showing countless faults forming in the sandstone.

Another feature of rock decay and weathering are these pools that form in the rock.  These are formed by a small depression filling with water. The water has small pebbles at the bottom. Wind blows the water and stirs it around which leads the pebbles to begin scraping away the rock around the edges.

Pool formed by wind, water, and time.

 
 In arid environments like the harsh Nevada landscape, continuous evaporation of available water, deposits load after load of salt molecules on the surface. The presence of these salts results in a type of rock decay that dominates these lithified sand dunes.

Salt weathering is a type of mechanical weathering which very slowly chips off pieces of the sandstone, one grain at a time. Previously believed to be the result of wind erosion, large holes in the rock (as seen in the picture below) developed by salt weathering represent some of the most iconic visuals of the park. Salt weathering however, does not begin by forming single large holes like the one I’m inside. Salt weathering, especially in sandstone, begins by forming small holes called alveoli. These tiny pits in the rock begin to expand and grow resulting in the formation of tafoni. After even greater periods of time as the salt continues to weather away the rock, resulting in the larger holes that a person cal climb into.

Tafoni forming in sandstone

Sources:
- http://digital-desert.com/valley-of-fire/index.html
- Pictures by Sam Epperly except for the tafoni picture which I found here: http://0.tqn.com/d/geology/1/0/4/I/1/voftafoni.jpg
- Slides from lectures