Despite the towering walls of granite that rim the Yosemite Valley in the heart of Yosemite National Park, the place is decidedly not static. Rather, it's a constantly evolving geologic entity that is both deadly and mesmerizing.
According to the geologists at Yosemite, "(R)ock falls are a natural and dynamic geologic process. Due to its steep, glacier-carved cliffs, Yosemite Valley experiences many rock falls each year. Historical records indicate that at least 600 rock falls have occurred in the park during the past 150 years. Massive piles of 'talus' or rock debris at the base of Yosemite Valley’s cliffs are reminders of these dramatic events. Natural processes like rock fall help to create the beautiful and changing scenery in Yosemite National Park, but they also present potential hazards."
In his latest production for Yosemite Nature Notes, videographer Steven M. Bumgardner has put together a great video that explains how, since the disappearance of glaciers about 15,000 years ago, rock falls have become the greatest erosional factor in the continued sculpting of Yosemite Valley.
For more information on rock falls in Yosemite, read this story from Traveler's archives.