Royal Arches
The Royal Arches is a cliff containing natural occurring granite exfoliation arches, located below North Dome and rising above Yosemite Valley, in Yosemite National Park, California. (). These are not literal arches, but rather arch shaped indentations in the cliff face. The Royal Arches are located on the north side of the valley, northeast of the Ahwahnee Hotel. Adjacent to the Royal Arches is the Royal Arch Cascade waterfall. Washington Column is just to the east, and North Dome is above. Geology and rockfall risk The Royal Arches, like many areas of Yosemite Valley, is prone to rockfall from the nearly vertical cliffs that surround the valley. Factors long known to trigger rockfall on steep cliffs include "precipitation, seismic activity and freezing conditions". Research conducted at the Royal Arches by scientists with the United States Geological Survey and the National Park Service analyzed the additional role of very hot weather on exfoliation. The researcers installed motion sensors in the crack behind a slab of granite on the Royal Arches that measures 19 meters tall, 4 meters wide, and 10 centimeters thick, and monitored the rock movement for 3-1/2 years. They learned that the crack could open up as much as