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Geomorphology

The study of landforms, including the description, classification, origin, development, and history of planetary surface features. Emphasis is placed on the genetic interpretation of the erosional and depositional features of the Earth's surface. However, geomorphologists also study primary relief elements formed by movements of the Earth's crust, topography on the sea floor and on other planets, and applications of geomorphic information to problems in environmental engineering.

Fig. 1  The great bar of Pleistocene Lake Bonneville at Stockton, Utah. (After G. K. Gilbert, U.S. Geol. Surv. Monogr. 1, 1890)

Geomorphologists analyze the landscape, a factor of immense importance to humankind. Their purview includes the structural framework of landscape, weathering and soils, mass movement and hillslopes, fluvial features, eolian features, glacial and periglacial phenomena, coastlines, and karst landscapes. Processes and landforms are analyzed for their adjustment through time, especially the most recent portions of Earth history.

Fig. 2  Surveying large transverse gravel bars created by flooding of the Medina River, Texas, in August 1978.

History

Geomorphology emerged as a science in the early nineteenth century with the writings of James Hutton, John Playfair, and Charles Lyell. These men demonstrated that prolonged fluvial erosion is responsible for most of the Earth's valleys. Impetus was given to geomorphology by the exploratory surveys of the nineteenth century, especially those in the western United States. By the end of the nineteenth century, geomorphology had achieved its most important theoretical synthesis through the work of William Morris Davis. He conceived a marvelous deductive scheme of landscape development through the action of geomorphic processes acting on the structure of the bedrock to induce a progressive evolution of landscape stages.

Perhaps the premier geomorphologist was Grove Karl Gilbert. In 1877 he published his report “Geology of the Henry Mountains.” This paper introduced the concept of equilibrium to organize tectonic and erosional process studies. Fluvial erosion was magnificently described according to the concept of energy. Gilbert's monograph “Lake Bonneville” was published in 1890 and described the Pleistocene history of the predecessor to the Great Salt Lake (Fig. 1). The monograph is a masterpiece of dynamic analysis. Concepts of force and resistance, equilibrium, and adjustment—these dominated in Gilbert's study of geomorphology. He later presented a thorough analysis of fluvial sediment transport and the environmental effects of altered fluvial systems. He even made a perceptive study of the surface morphology of the Moon.

Fig. 3  Streamlined uplands and large sinuous channels in the Chryse Planitia region of Mars. (National Aeronautics and Space Administration)

Despite Gilbert's example, geomorphologists in the early twentieth century largely worked on landscape classification and description according to Davis's theoretical framework. Toward the middle of the twentieth century, alternative theoretical approaches appeared. Especially in France and Germany, climatic geomorphology arose on the premise that distinctive landforms and processes are associated with certain climatic regions. Geomorphology since 1945 has become highly diversified, with many groups specializing in relatively narrow subfields, such as karst geomorphology, coastal processes, glacial and Quaternary geology, and fluvial processes.

Process geomorphology

Modern geomorphologists emphasize basic studies of processes presently active on the landscape (Fig. 2). This work has benefited from new field, laboratory, and analytical techniques, many of which are borrowed from other disciplines. Geomorphologists consider processes from the perspectives of pedology, soil mechanics, sedimentology, geochemistry, hydrology, fluid mechanics, remote sensing, and other sciences. The complexity of geomorphic processes has required this interdisciplinary approach, but it has also led to a theoretical vacuum in the science. At present many geomorphologists are organizing their studies through a form of systems analysis. The landscape is conceived of as a series of elements linked by flows of mass and energy. Process studies measure the inputs, outputs, and transfers for these systems. Although systems analysis is not a true theory, it is compatible with the powerful new tools of computer analysis and remote sensing. Systems analysis provides an organizational framework within which geomorphologists are developing models to predict selected phenomena.

The future

Geomorphology is increasing in importance because of the increased activity of humans as a geomorphic agent. As society evolves to more complexity, it increasingly affects and is threatened by such geomorphic processes as soil erosion, flooding, landsliding, coastal erosion, and sinkhole collapse. Geomorphology plays an essential role in environmental management, providing a broader perspective of landscape dynamics than can be given by standard engineering practice.

The phenomenal achievements of nineteenth-century geomorphology were stimulated by the new frontier of unexplored lands. The new frontier for geomorphology in the late twentieth century lies in the study of other planetary surfaces (Fig. 3). Each new planetary exploration has revealed a diversity of processes that stimulates new hypotheses for features on Earth. Geomorphology must now solve the mysteries of meteor craters on the Moon and Mercury, great landslides and flood channels on Mars, phenomenally active volcanism on Io, and ice tectonics on Ganymede. See also: Coastal landforms; Erosion; Glaciated terrain; Karst topography

Victor R. Baker

Bibliography

V. R. Baker and S. J. Pyne, G. K. Gilbert and modern geomorphology, Amer. J. Sci., 278:97–123, 1978

A. L. Bloom, Geomorphology: A Systematic Analysis of Late Cenozoic Landforms, 3d ed., 1997

A. F. Pitty, Geomorphology: Themes and Trends, 1985

D. F. Ritter, Process Geomorphology, 3d ed., 1995

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