The "South Window" arch at Arches National Park, near Moab, Utah, on June 30, 2009.
CNET News reporter Daniel Terdiman spent two days in eastern Utah on Road Trip 2009, and visited Arches, Canyonlands National Park, Monument Valley Navajo Tribal Park and the outstanding scenic route of Utah highway 128 that leads to Moab.
Formations like the Southern Window, as well as others in Arches National Park happen for a number of different reasons. "Cracks in fins and the contact layer between different layers of rock are good places for arches to begin," an information display at the Arches visitor center explains. "Both mechanical and chemical forces attack these weaker spots and begin the processes which form arches."