A History of Erosion Cycle Theory and Its Influence on Japanese Geomorphology

The erosion cycle theory is the core of Davisian geomorphology, distinguishing geomorphology from geology by its deductive method. The concept of an erosion cycle is an. idea or a philosophical system which is composed of a number of important concepts (for instance: base-level, grade, peneplanation) that were developed in the 19th century by Davis aimed to explain landscape by the deductive method in terms of evolution rather than catastrophe. He believed that landforms change as organisms do, through a sequential series of changes. In so far as he believed that landscapes evolve through young, mature, and old stages, he had to postulate a cycle of rapid uplift followed by erosion. Slow uplift and overwhelming erosion or moderate uplift and moderate erosion, as suggested by A. Penck, are also possible, but Davis simplified the model for educational purposes.<br> The basic hypothesis of the generally accepted erosion cycle has two main points: (1) landform development is sequential, and (2) peneplanation, as shown by accordance of ridges of the Appalachian Highlands, is universal throughout geological time. This basic hypothesis is so magnificient and spectacular that it captivated the imaginations of a number of geologists and geographers.<br> The concept of erosion cycle was developed in two ways: geographical deduction for explanatory <br>description of Land forms and geological deduction for determining denudation chronology. In each type of deduction, we can see that the ideological concept of erosion cycle was abandoned after extensive discussion and arguement. The reason is that the erosion cycle theory is based on a number of philosophical inferences.<br> As the reason for the overwhelming popularity of erosion cycle theory, we can suggest the following: 1) it had evolutional philosophy behind it, which was the mainstream of contemporary scientific thought. 2) Davis explained it persistently in a way that was easy to understand. And I can add that the use of it was pragmatic. Generally speaking, the more magnificent a hypothetical theory is, the more researchers feel like obtaining magnificent results, even if only a fraction can be confirmed. This arouses scientists' interest. In this way, the Davisian system of geomorphology endured for a long time, and scientists' expectations of it were too high.<br> Davis was well aware that his theory was based on a number of inferences. Neverthless. he still defended it stubbornly in his later years, until he was over 80.<br> Davisian geomorpholgy was prevalent from 1900 to 1930, and began to be criticized in the 1930's. By the 1950's it had been discredited.<br> In Japan, at the beginning, geomorphological studies were done by geologists. Under the influence of German geographers, Japanese geomorphology grew independent from geology around 1920. The Davisian system of geomorphology was introduced in Japan by Taro Tsujimura in 1920. At the same time the arguements against Davisian geomorphology, advanced by famous German geographers like A. Hettner and A. Penck were known to Japanese geomorphologists. Although Gakuro Imamura of the German school strongly argued against Davisian geomorpholgy, it was gradually accepted under the leadership of Tsujimura. The theory was so simple, understandable, and practical that it attracted younger geomorphologists. The first textbook of geomorphology in Japanese was written by Tsujimura in 1922. Since then, the erosion cycle theory has been explained in every geomorphological textbook in Japanese.<br> Denudation chronology, which was not part of Davis' original theory, was not advocated by Tsujimura. But it began to be adopted gradually by geologists. After World War II, a number of geomorphologists gradually followed the geologists in accepting denudation chronology.<br> In 1953, Tsujimura's geomorphology (Davisian deductive geomorphology) began to be criticized by geologists and younger geomorphologists.