What Is Geomorphology?

The term geomorphology is derived from three Greek words: geo (earth), morph (forms) and logus (science). It is, thus, the science of earth forms or land forms. It is also defined as the interpretative description of the relief features of the earth’s surface. The word physiography was thought to be synonymous of geomorphology and, in the early days, was included both in geology and geography courses. Geographers study this branch as a discussion of the land forms with respect to man’s environment, i.e. how’much they are useful to man.

Moreover, they do not give much importance on the origin of the land forms. Gradually, there has been a decline of interest among geographers in this branch. As a result, geomorphology becomes primarily a part of geology in which the origin of the land forms are given due cognizance.

History and background of geomorphology: The science of land forms is too old and dates back to Herodotus (485? – 425 B.C.), the father of history. The history of modern geomorphology dates back to James Hutton (1726 – 1797), who propounded the doctrine of ‘Uniformitarianism’ i.e., the present is the key to the past’.

Hutton has nicely described the fact that the rivers, glaciers, seas had been doing the same work since their inception, as they are doing it today, may be at different rates at different times. John Playfair (a great friend of Hutton, 17481819) elaborated and expounded Hutton’s principle in form of scientific writings, Lyeril (1797-1875) is also a great exponent of the theory of ‘Uniformitarianism’. Major Powell (1834-1902) contributed a lot to geomorphology on his study in the

Colorado Plateau and the Grand Canyon of the Colorado river during his expedition. It is W.M. Davis (1850-1934), the great definer, analyst and systemizer, who gave new concepts to modern geomorphology by his genetic methods of the description of the land forms.

Till recent times, geomorphology was a much neglected branch. Its importance increased only after the applications of geomprphic studies to other branches of geology. Practical applications of geomorphic principles to hydrology, pedology, engineering geology, petroleum geology, economic mineral deposits, mining and such other fields increased the importance of this branch of science.

In recent years, branches like regional, quantitative and experimental geomorphology have gained much importance. The importance of geomorphology has increased manifold after the development of aerial and satellite remote sensing. All kinds of remote sensing studies and their applications are incomplete without the study of geomorphology.

Mountain

 Land forms: As geomorphology means the science of earth forms and features, a knowledge of the relief features becomes essential. The relief features of the earth are broadly divided into three orders. The first order relief features are the Continental platforms and the ocean basins. There are mountains, plateaus and plains on the continental platform and the ocean basins; these are the second order relief features.

All the minor landforms on the mountains, plateaus and the plains, to name a few – hills, mesa, buttes, mounds, dunes, valleys, flood plains, deltas, kames, eskers, drumlins, terraces, pediment, bajada, beach, coast etc, are the third order relief features. Plateau Continental shelf Costal plain Continental slope Ocean: basin Fig.2.1: Relief features of the earth

Geomorphic Precesses and Agents: All those physical and chemical processes that modify the earth’s surface forms are termed as geomorphic processes. A geomorphic agent is any natural medium that is capable of scouring and transporting earth material. Thus, running water, underground water, glaciers, wind, waves, currents, tides and tsunamis are the geomorphic agents.

They are also called as geologic agents or mobile agents. These agents originate outside the earth’s crust and the work performed by them act at or near the earth’s surface. For this reason, they are termed as exogenetic or epigene processes. They tend to bring the earth’s surface to a common level, that is, they degrade the highlands and aggrade the low lands. For this, they are also termed as gradational agents. The processes are gradational processes. Earth’s surface is also modified by weathering and masswasting processes. All these processes are exogenetic or epigene processes.

Other geomorphic processes, such as diastrophism and volcanism originate within the earth’s interior and modify the earth’s surface. These are endogenetic or hypogene processes. Earth’s surface is also affected by the impact of meteorites. This is an extra-terrestrial process. The different geomorphic processes are outlined in Table 2.1.

WEATHERING

Weathering: Weathering is the disintegration and or decomposition of rocks in situ or in place. This includes a group of processes that act collectively at and near the earth’s surface. They fragment the solid rocks and convert them into clastic state. The portion of the earth’s crust which is exposed to the weathering processes in known as the zone of weathering. Rock weathering is broadly divided into three types (i) Physical weathering (ii) Chemical weathering and (iii) Biological weathering.

Leave a Comment