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Wednesday, 6 June 2018

Basic concepts in geomorphology

In the term geomorphology 'geo' means earth and 'graphos' means landforms, which basically means that it is a systematic and organized description and analysis of the landforms of earth. It has resulted in the development of the Basic concepts in geomorphology which has a crucial impact in today's world.
Geomorphology has resulted a great change from ancient days till now, resulting in the generation of The Basic concepts in geomorphology  that which are been discussed below.

There are ten basic concepts in geomorphology. Each concept differs from the other in various aspects. Let us now look upon these ten basic concepts.

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Basic concepts in geomorphology 

Concept - 1 "The same physical process and the law operated today all throughout the geological time not necessarily with the same intensity as now."

(i) This very principle, is considered to be underlined principle of the modern geology. It is also known as principle of uniformatarianism. 

(ii) This principle was first put forwarded by James Hutton in the year 1785.

(iii) In the year 1802, it was elaborated by Playfair. Further, in the book 'Principles of geology', it was made popular by Charles Lyell.

(iv) According to James Hutton, 'Present is the key to the past.' He cited the following example , Glaciers were much more significant in the Pleistocene period of geological time than now.

Concept - 2 "Geological structure is a dominant control factor in the evolution of landforms and is reflected in them."

(i) The structure along with types, folding and folding of rocks also means hardness, permeability and chemical properties of rocks.

(ii) The difference in structure and nature of rock has its affect on the rate of weathering and erosion on the earth.
 
(iii) The climatic conditions, temperature, precipitation, soil and humidity also have its affect on the rate of the processes.

(iv) Example, water seeps down easily through the permeable sandstone rock, due to which the surface floor is less and number of stream is also less. But water cannot easily seep down through impermeable shale rock, due to which the surface floor is more and number of stream is also more.

(v) The permeability of rocks depends upon the joints and bedding plane.

Concept - 3 "To a large extent, the earth's surface possess relief because the geomorphic process operate at differential rate."

(i) There are various types of relief features on the earth's surface, which ate formed by endogenetic and exogenetic processes.

(ii) The process of gradation varies from place to place due to lithology and disposition of rock layers.

(iii) The highlands are formed by hard rocks and the lowlands are formed by soft rocks.

(iv) Factors like temperature, moisture, altitude, topographic configuration and amount of vegetative cover also are related to structure and lithology.

Concept - 4 "Geomorphic process leave their distinctive imprint upon landforms and each geomorphic process develops its own characteristic assemblage of landforms."

(i) The physical and chemical processes which are grouped into endogenetic and exogenetic  processes, are basically included in the geomorphic process.
 
(ii) The endogenetic process operate inside the crust at an extreme fast rate. While, the exogenetic process operate at the surface of earth removing the irregularities at an extreme slower rate.

(iii) Each process do not operate in isolation with the other. More than one process can be active at a particular point of time.

(iv) The different geomorphic processes which are active in a complex manner at a particular point of time are collectively known as morphogenetic system.

Concept - 5 "As different erosional agents act upon the earth's surface, there is produced an orderly sequence of landmass."

(i) Various geomorphologists have a believe that the different landforms are formed in an orderly and sequential manner.

(ii) The use of the term 'geomorphic cycle', cannot be ignored completely.

(iii) The whole landscape of our earth keeps on changing constantly, as the earth revolves continuously.

Concept - 6 "Complexity of geomorphic evolution is more common than simplicity."

(i) Though there are different processes and resultant landforms, but in reality, there is hardly a region where more than one process is active. More than one process operate simultaneously in a particular area.

(ii) The landform evolution is not related with one cycle of erosion, rather it is a result of numerous erosional cycles.

(iii) In 1952, Herberg has divided the landscape into five categories, 

a) Simple landscape - They are formed by one significant geomorphic process.

b) Compound landscape - They are formed by more than one geomorphic processes.

c) Mono cyclic landscape - They are formed by one cycle of erosion. Eg, volcanic cone, lava plain, uplifted ocean floor etc.

d) Multi cyclic landscape - They are formed by more than one cycle of erosion. Eg, river valley, river terrace, moraine etc.

e) Exhumed landscape - They ate formed in the geological past and were buried under igneous and sedimentary rocks. Due yo denudation, the outer layer of rock got removed at later stage and this particular landscape appeared.

Concept - 7 Little of the earth's topography is older than tertiary and most of it not older than the Pleistocene.

(i) All the topographic features are rare. Some of them exist but in exhumed form.

(ii) It is considered that geological structures are much more older than the topographic features. 

(iii) Example, the Himalayas are fast folded mountains developed in the Cretaceous and Miocene period. But the present day elevation of the Himalayan mountains was not attended until the Pleistocene period.

Concept - 8 Proper interpretation of the present day landscape is impossible without a full appreciation of the manifold influences of the geologic and climatic changes during Pleistocene.

(i) The geological climatic changes of the Pleistocene period had influences upon the topographic features of the present day.

(ii) Glaciation has affected areas of million squares miles but sometimes it is considered that it has affected beyond the amount of areas mentioned.

(iii) Although the process of glaciation was significant during the Pleistocene period of geological time, it shouldn't be avoided that the process of diastrophism continued in the Pleistocene period.

Concept - 9 An appreciation of world climate is necessary to a proper understanding of the varying importance of the different geomorphic processes.

(i) The variation in climate affects the process of geomorphic agents directly or indirectly. The direct factors are precipitation, temperature, wind velocity, wind direction etc. The indirect factors are related to the affect of climate to the amount, kind and distribution of vegetal cover.

(ii) The other factors are amount of rainfall, difference between leeward and windward side, climatic influence related with slope etc.

(iii) The factors that are dominant in the humid middle latitudes are not same in the higher and lower latitudes and their differences are influenced by the climatic conditions.

Concept - 10 Geomorphologically although concerned primarily with present day landscape, attains its maximum usefulness of historical extension.

(i) Geomorphology concerns itself with the development of the present day landscape. The principle of uniformatarianism is related with this.

(ii) The identification of the ancient erosion surface and study of topography is known as Paleo Geomorphology.

(iii) Bryan identified the historical event of geomorphology in the year 1941. His opined that if the landforms were the result of the of the present processes, there would not be a separation for the study of landforms as a field of effort which is distinct from the dynamic geology.

(iv) In the essence and methodology of it, physiography is considered to be historical.

From above, we got a overall idea what the Basic concepts in geomorphology deals with. Each of these concepts had influence on the present day world. There is link of each concept with other but at the same time it differs from each other.

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