This alluvial fan extends out from a "wineglass" canyon. A wineglass canyon has a narrow neck and a widening upper portion. Active uplift of the mountains results in a narrow neck that is relatively young, and has had less time to erode than the higher uplands. Note the differing colors of gravel. In general older gravels are darker, allowing geologists to map the depositional history.
All images copyright © 2006 F.W. Vollmer and may not be used without permission.