What is Geomorphology?

Geomorphology is a branch of Geography, which is similar to the subject of Geology. It deals with the study, origins, development and classification of the landforms. It also discusses the processes impacting on the landforms. These processes shape the Earth’s surface, such as weathering, erosion, tectonic activities and volcanism. Geomorphologists investigate the topography of the Earth and seek to understand the forces and factors that contribute to the formation of various landforms, including mountains, valleys, plains, and coastlines.

Nature of Geomorphology

The rapidly evolving discipline of geomorphology has undergone a notable transformation in methodology and approaches to the study of landforms and related processes since 1945 when R.E. Horton introduced quantitative methods of analysis of morphometric characteristics of fluvially originated drainage basins. A clear-cut cleavage surfaced in the discipline in the form of an evolutionary approach involving progressive landform changes through long periods and a process-response approach involving an equilibrium model and a steady state of landform development after 1950. Thus, the need of the time is to integrate the cyclic concept involving
long-term historical evolution of landforms and noncyclic concepts involving dynamic equilibrium, functional and process-response models on the one hand, and micro-geomorphology involving smaller spatial and temporal scales and mega-geomorphology involving larger spatial and longer temporal scales on the other hand.

Etymology of Geomorphology

Geomorphology is a significant branch of physical geography (others are hydrology, climatology, and biogeography), which stems from three Greek words i.e. “geo” meaning Earth, “morphe” meaning forms, and “logos” meaning discourse. Geomorphology, therefore, is defined as the science of description (discourse) of various forms (morphe) of the earth’s surface. To be more precise, forms mean topographic features or geometric features (relief features) of the earth’s surface. P.G. Worcester (1940) preferred to define geomorphology as the interpretative description of the relief features of the earth’s surface while W .D. Thornbury (1954) pleaded for including submarine forms in addition to surface reliefs in the realm of geomorphology.

Geomorphology may be defined as the scientific study of surface features of the earth’s surface involving interpretative description of landforms, their origin and development and nature and mechanism of geomorphological processes which evolve the landforms with a view that ‘all landforms can be related to a particular geologic process, or set of processes, and that the landforms thus developed may evolve with time through a sequence of forms dependent in part, on the relative time a particular process has been operating’ (Easterbrook, 1969). A.L. Bloom (1979) also defined geomorphology as the systematic description and analysis of landscapes and the processes that change them.

Scope of Geomorphology

The subject matter of geomorphology may be organized on the basis of (i) dimension and scale of relief features (landforms), (ij) processes that shape the landforms, and (iii) the approaches to the geomorphic studies. In fact, geomorphology, being a study of landforms, has a well defined framework of its subject matter. The systematic study of landforms requires some fundamental knowledge of geology as the genesis and development of all types of landforms primarily depend on the materials (geomaterials or structure) of the earth’s crust and partly on the forces coming from within the earth (endogenetic forces).Based on this connotation geomorphology is, some times, equated with geology (W.D. Thornbury, 1954) and sometimes is considered a branch of geology (A.K. Lobeck, 1939).

In fact, geomorphology has originated from geology and in most of the American Universities it is still housed in geology departments. Thus, some aspects of geology, even today, are included in the description and analysis of landforms e.g. structural and dynamic geology. Theoretical geology helps in understanding the nature of landforms and, therefore, the origin of different types of reliefs like mountains, plateaus, continents and ocean basins on which the microlandforms are evolved must be properly understood. Endogenetic forces particularly diastrophic and sudden (vulcanicity and seismic events) should be taken note of as they introduce irregularities on the earth’s surface, which generate variety in landforms. Thus, on the basis of dimension and scale, the relief features of the earth’s surface, the core subject matter of geomorphic study, may be grouped in three broad categories of descending order.

    1. Relief features of the first-order
    2. Relief features of second-order
    3. Relief features of third-order

Relief features of the first-order

‘On the smallest scale and covering the largest area is world geomorphology’ (C.A.M. King, 1966) which includes consideration of continents and ocean basins. The consideration and interpretation of worldwide erosion surfaces requires the description and analysis of the characteristics and evolution of continents and ocean basins. Thus, continents and ocean basins become the relief features of the first order. The consideration of continental drift, in one way or the other, caused either by the forces coming from within the earth (thermal convective currents) involving plate tectonics or from outer sources (tidal forces, gravitational forces etc.), becomes desirable for the analysis of major morphological features of the earth’s surface. Plate tectonics help in understanding the origin of continents and ocean basins.

Relief features of the second-order

The structural forms developed over a continent or part thereof as mountains, plateaus, lakes faults, rift valleys etc. constitute the category 0f relief features of the second order. These forms owe their genesis mainly to endogenetic forces particularly diastrophic forces. The nature, mode and rate of operation of these endogenetic forces must be studied properly so that general characteristics, nature and mode of origin of the second-order relief features, upon which the third-order reliefs are produced, are well understood. These are called as constructional landforms.

Relief features of the third-order

Micro-level landforms developed on second-order relief features by exogenetic denudational processes originating from the atmosphere are included in this category. These landforms may be erosional (e.g. glacial valley, river valley, karst valley, cirques, canyons, gorges, terraces, yardangs, sea cliffs etc.), depositional (e.g. drumlins, eskers, flood plains, natural levees, delta, sea beaches, sand dunes, stalactites, stalagmites etc.), residual (e.g. monadnocks, inselbergs or bornhardts etc.) and some times minortectonic features (by endogenetic forces).
In fact, the relief features of the third order are given more importance in geomorphic studies as they constitute the core of the subject matter of geomorphology. Besides, the nature, mode and rate of operation of denudational processes, which produce the relief features of the third order, are also studied at varying spatial and temporal scales. Besides natural geomorphological processes, anthropogenic processes are also attached due importance in geomorphic investigation because the role of man as ‘economic and technological m an’ through his economic activities has augmented the rate of natural processes beyond imagination (chapter 30).

The subject matter of geomorphology may also be organized on the basis of geomorphic processes (both endogenous and exogenous) that shape the landforms and approaches to the study of landforms. Davisian dictum that ‘landscape is a function of structure, process and tim e’ and K.J. Gregory’s geomorphic equation (F=f (PM)dt, where F = landforms, f = function of, P = processes, M =geomaterials, dt = mathematical way of denoting change over time) clearly reveal that any geomorphic study requires careful investigation of geomorphological processes (mainly denudational processes), geomaterials (lithology, disposition of rock beds and composition of rocks, collectively known as structure) and time factor, though the advocates of dynamic equilibrium theory have pleaded for exclusion of time factor on the basic premise that the landforms are time-independent. Geomorphic studies incorporate two major approaches viz. historical studies involving historical evolution of landforms and functional studies involving time independent series o f landform evolution reflecting association between landform characteristics and existing environmental conditions. Both approaches have their relevance in geomorphological investigations.

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