Penck, A. (1859–1945), Penck, W. (1888–1927) In the early part of the twentieth century, when landscape studies in North America, Britain, and France were in the stranglehold of W. M. Davis's cycle of erosion, German geomorphologists, led by Albrecht Penck, and championed by his son, Walther, offered an alternative view of landscape evolution as a response to ongoing crustal movements (tectonism). The basic dichotomy between the Davisian and Penckian schemes is sharply illustrated in their contrasting views on how mountain landscapes evolve. To Davis, the accordance of summits in various mountain ranges represented the remnants of pre-existing erosional surfaces (peneplains) that had been uplifted by short-lived pulses of tectonism and subsequently passively eroded and shaped by progressive downwearing. In contrast, Albrecht and Walther Penck argued that accordant summits, rather than being the inherited ‘floors’ of previous denudational episodes, were upper limits to which mountains could grow and were limited because maximum uplift rates balanced denudation rates at these elevations. Albrecht Penck's research was undertaken in the European Alps, and it was in providing the first unified framework for understanding the Pleistocene history of this mountain range that he made his notable contribution. His model, developed with E. Bruckner, of four main glacial phases—Gunz, Mindel, Riss, and Würm—was immensely influential, although it has since been superseded by a more complex Pleistocene history determined on the basis of deep-sea core studies. It was Walther Penck, however, working in the European mountain ranges as well as further afield in the Andes, who provided the real (and arguably the only major) contemporary challenge to Davisian theory.
The central tenet of Walther Penck's work was that landforms resulted from the opposing tendencies of exogenetic processes (i.e. weathering and transport) and endogenetic (crustal) processes. In contrast to the faulted basin-and-range topography expounded by Davis, Penck considered folding as the main relief-producing crustal process. Furthermore, at the core of his view of landscape evolution was a vision of slope development that was dominated by mass movement. Penck considered that where rates of denudation are declining, hillslopes evolve through a process of flattening from the base upwards. In effect, each part of the slope profile is replaced by a slope of lower gradient as it retreats, and through this process of ‘slope replacement’, a broadly concave profile is produced. Penck's inability to illustrate his often complex ideas with convincing diagrams contrasted markedly with the artistic ability and skilful advocacy of Davis, which allowed him to misrepresent Penck's concept of slope replacement as one of ‘parallel retreat’ of the major part of the slope. With the comparative obscurity of Penck's original German papers, and then his early death in 1927, the general view of his work was long dominated by Davis's misinterpretations. In 1953, Penck's views were somewhat clarified for a wider audience by the English translation of his main work,
Die Morphologische Analyse, and in the 1970s his deductive reasoning on the nature of mass-movement processes began to be incorporated into emerging process–response models. During the 1980s and 1990s, increasing research into active tectonic processes revealed the remarkable prescience of many Walther Penck's observations on the interplay between crustal movements and surficial processes, and promises a rekindling of interest in his ideas.
Iain S. Stewart
Bibliography
Beckinsdale, R. P. and and Chorley, R. J. (1991) The history of the study of landforms or the development of geomorphology. Volume 3: Historical and regional geomorphology 1890–1950.Routledge, London.
