Joshua Tree National Park - Arch Rock
Posted by: 
TerryDad2
N 33° 59.184 W 116° 00.941
11S E 590915 N 3761084
This natural arch is located along a well posted geologic nature trail that starts in the White Tank Campground. The trail ranges from loose sand to hard rock with steps. There are great signs posted along the trail with additional geologic information about the area.
Waymark Code: WMN9Y
Location: California, United States
Date Posted: 08/24/2006
Views: 108
This natural arch formed in the White Tank Granite. This igneous rock is thought to have pushed its way up into the surrounding Pinto Gneiss between 135 to 155 million years ago creating a large pluton (see other earthcache). This pluton cooled slowly allowing the relatively large crystals of quartz, feldspar, and biotie to form.
Through a variety of erosional processes, an arch was formed in the granite. Jointing (see other earthcache) created lines of weakness in the massive granite pluton. Water dissolved the rock surface and seeped into small cracks where it froze and expanded causing the small cracks to get larger. By chance, the result of the erosion created the arch.
Photo of the Arch by itself?: yes
Type of Arch: Water Eroded
Type of Material:
White Tank Granite
Jointing created lines of weakness in the massive granite pluton. Water dissolved the rock surface and seeped into small cracks where it froze and expanded causing the small cracks to get larger. By chance, the result of the erosion created the arch.
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Visit Instructions:
You must post a picture of you with a GPSr or Geocaching/Waymarking attire/equipment and the subject arch in the background.