The geographical cycle of erosion as envisaged by Davis is a geographical model and an early paradigm in geomorphology. His work has proved to be a simple and effective vehicle for teaching, and it had a profound effect on the development of geomorphology in the English speaking world.
Davis had great breadth of interest as is evidenced by his keen interest in glacial, coastal, arid, and volcanic landforms in addition to the cycle of erosion. Davis changed his views considerably later on, particularly on the universal applicability of the normal cycle.
He admitted that there was a need for separate cycles in arid and glacial areas. Davis published his basic thesis on the cycle of erosion in 1899, considered some complications regarding the cycle in 1904, and brought his main ideas together in a single work in 1909.
Besides, in the next 30 years he continued to modify and extend his views in different ways by publishing papers.
The concept of base level is crucial in his thesis. He also examined the effect of repeated minor uplifts in detail. He argued that many landscapes are polycyclic in origin.
He was also in the knowledge of the fact that the cycle of erosion, because of climatic change, might not be able to run its full course. Glaciations, aridity and vulcanicity were considered by him as interruptions of the cycle and called them ‘accidents’.
He was also convinced to formulate a separate cycle for arid regions. It is true that his approach was historical as he had a long view of the landscape.