A view of the talus, or weathered rock debris, that mantles the slopes within the gorge. The size and shape of the blocks is determined by the spacing of the natural joints (fractures) within the quartzite. Blocks are commonly 4-5 ft. along each side. The grey color of the talus is due to lichen that covers each block (otherwise the rock itself is purplish). The slope angle is a steep 20 degrees. This angle, termed the "angle of repose" of the material, is determined by the balance of forces between gravity (which acts to pull the slope down) and the resistance of the material to such motion. This resistance (the "internal friction" of the slope) is largely a product of the angular shape of the fragments.