Abstract
The most popular theories for the origin of the form of the earth's surface features suppose that they have been sculptured during vast time periods by erosive processes similar in rate, scale and intensity to modern processes. The theory that dominates modern geomorphology was formulated nearly a hundred years ago by William Morris Davis, a Harvard geologist. He supposed that landscapes did not develop haphazardly, but evolved through a series of stages as the stream drainage slowly eroded channels upslope and as valleys were progressively widened and deepened. According to Davis, the "youthful" stage of landscape evolution immediately follows uplift and is characterized by poor drainage, and narrow, V-shaped valleys between flat and wide interstream divides. After a few millions of years of erosion, the maximum relief "mature" stage would be achieved with well-integrated stream drainage, and deep, wide valleys, between narrow and rounded interstream divides. Finally, if erosion continued unchecked, the landscape could enter the "old age" stage where the surface becomes a poorly drained "peneplain" with streams of low gradient meandering over extensive flood plains at elevations just above sea level.