February 12, 1850 - February 5, 1934,Davis, who was born in Philadelphia, Pennsylvania, was educated at Harvard. He returned to teach there in 1877 after a period as a meteorologist in Argentina and as an assistant with the North Pacific Survey. He became professor of physical geography in 1890 and of geology in 1898. Davis is acknowledged as the founder of geomorphology, the study of landforms. In his The Rivers and Valleys of Pennsylvania (1889) he first introduced what later became known as the Davisian systems of landscape analysis. His aim was to provide an explanatory description of how landforms change in an ideal situation and his most important contribution to this was his introduction of the cycle of erosion into geographical thought. He proposed a complete cycle of youth, maturity, and old age to describe the evolution of a landscape. In youth rivers occupy steep V-shaped valleys while in old age the valleys are broad. The end product would be a flat featureless plain he called a epeneplaine. This was an ideal cycle but in practice the cycle would invariably be interrupted by Earth movements. It was, nevertheless, strongly attacked by German geographers who objected to it on the grounds that it neglected such vital factors as weathering and climate in transforming the landscape. They also believed him to be undermining their argument that landforms could only be discovered by local fieldwork and the production of regional monographs. Davis also produced an influential work,