Arch Rock is a natural formation in the Valley of Fire State Park in Nevada.
Although there was a natural arch collapse in the park back in May 2010, it wasn’t this particular arch. This arch appeared in a YouTube video by Bobby Swetz taken January 15, 2011 according to his narration.
Natural arches are formed due to the differing hardness of volumes of the sandstone exposed to the elements. The softer stone gets weathered faster. Ultimately though, the weathering gets to key parts of the arch and they collapse.
In this arch you can clearly see a rock joint to the right of the top of the arch where the fault line that enters the frame at bottom left cuts through. You can see that this is a weak spot by the way to top of the arch cuts in. This arch too will collapse at some point in the future as this joint gets progressively weakened through the freeze-thaw cycle.
Below, just for grins, is a color version.
Camera: Canon EOS 5D
Lens: Canon EF17-35mmf/2.8L USM
Processing: Lightroom 4.0
Processing: Photomatix 4.02
Processing: Photoshop CS5
Processing: Nik Software Silver Efex Pro 2 (Nik Software)
Processing: Nik Software Color Efex Pro 4 (Nik Software)