Stream gradients increased on flanking mountain ranges as they were uplifted. These swifter moving streams are dry most of the year but have nevertheless cut true river valleys, canyons, and gorges that face Death and Panamint valleys. In this arid environment, alluvial fans form at the mouth of these streams. Very large alluvial fans merged to form continuous alluvial slopes called "bajadas" along the Panamint Range. The faster uplift along the Black Mountains formed much smaller alluvial fans because older fans are buried under playa sediments before they can grow too large. Slot canyons are often found at the mouths of the streams that feed the fans, and the slot canyons in turn are topped by V-shaped gorges. This forms what looks like a wineglass shape to some people, thus giving them their names, "wineglass canyons".