Write notes on any three concepts of Geomorphology.
Answers
The basic or
fundamental concepts of geomorphology are as follows:
1. The same physical processes and laws that operate today operated throughout geologic
time, although not necessarily with the same intensity as now.
This is the important principle of geology and is known as the principle of
uniformitarianism. It was first enunciated by Hutton in 1785. According to Hutton "the present is
the key to the past". According to him geologic processes operated throughout geologic time with
the same intensity as now. We know that it is not true. Glaciers were much more significant during
the Pleistocene and during other periods of geologic time than now; world climates have not
always been distributed as they now are, and, thus, regions that are now humid have been desert
and areas now desert have been humid. There are numerous examples which shows that the
intensity of various geologic processes has varied through geologic time.
2. Geologic structure is a dominant control factor in the evolution of landforms and is
reflected in them.
The major controlling factor in land form development is structure and process. Here the
term structure includes not only the folds, faults etc. but all those ways in which the earth
materials out of which land forms are carved differ from one another in their physical and
chemical attributes. it includes such as rock attitudes; presence or absence of joints, bedding
planes, faults, and folds; rock massiveness; hardness of constituent minerals; the susceptibility of
the mineral constituents to chemical alteration; permeability and impermeability of rocks; and
various other ways by which the rocks of the earth crust differ from one another. The term
structure also has stratigraphic implications, and knowledge of the structure of a region implies as
appreciation of rock sequence, both in outcrop and in subsurface, as well as regional relationship
of the rock strata.
In general the structures are much older than the geomorphic forms developed upon
them. Such major structural features as folds and faults may go back to far distant periods of
diastrophism.
3. To a large degree the earth's surface possesses relief because the geomorphic
processes operate at different rates.
The rocks of the earth's crust vary in their lithology and structure and hence offer varying
degrees of resistance to the gradational processes. Differences in rock composition and
structures are reflected not only in regional geomorphic variability but in the local topography as
well. The local intensity of particular processes may change notably in response to differences in
such factors as temperature, moisture, altitude, exposure, topographic configuration, and the
amount and type of vegetal cover. The microclimatic conditions may vary markedly between a
valley floor and a hilltop, between a northern and a southern exposure, and between bare ground
and that with a heavy vegetal cover. The rate of all weathering, all mass-wasting, all erosion, and
all deposition varies appreciably within rather narrow limits in relation to the influence of local
conditioning factors.