1.1 Definition
Physical geography is one of the two branches of geography viz. physical geography and human geography. In fact, the study of physical aspects of the earth represents the core of spatial science i.e. geography. Most of geogra phers have pleaded for bifurcation of geography into physical and human geography but it is rather unwise to ingnore biotic aspect of the biospheric ecosystem of the earth and hence there should be trifurcation of geography into physical geogr phy, human geography and biogeography. Physi cal geography in terms of its meaning and definition, scope (subject matter) and methods of study has undergone seachange in the past few decades. In the beginning, physical geography was defined as the study of only physical environ ment (namely reliefs, air and water) of the earth e.g. the study of physical environment by itself is physical geography which includes consideration of surface relief of the globe (geomorphology), of the seas and the oceans (oceanography) and of the air (meteorology and climatology)' (Arthur Holmes).
1.2 Scope of physical Geography
First, the origin, age and structure of the
interior of the earth, isostasy and evolution of Fontinents and ocean basins are studied inorder to anderstand the characteristic features of the afore said four components. The study of forces or movements of the earth, both endogenetic (origi- nating from within the earth) and exogenetic (originating from the atmosphere) becomes sig nificant to understand the interactions between these two forces and resultant features. In fact, endogenetic forces (termed as constructive forces) coming from within the earth, create reliefs of varying dimensions on the earth's surface (e.g. mountains, folds, faults, volcanic cones etc.) which provide habitats for living organisms of the biospheric ecosystem on the one hand, and present initial reliefs for the interplay of exogenetic forces originating from the atmosphere, termed as destructive forces (denudational processes e.g. fluvial, marine, glacial, aeolian, periglacial etc. processes and weathering agents) on the other hand. The study of evolution of continents and ocean basins and their drifting (continental drift as evidenced by plate tectonics) helps in the understanding of evolution and dispersal of plants and animals.
1.3 Development of Physical Geography
The discipline of physical geography has evolved through successive stages of its develop- ment in terms of methodology and approaches to study. After taking its birth in the philosophical ideas and reports of ancient thinkers, philosophers and historians of the ancient seats of civilization and culture e.g. Greece, Rome and Egypt, the science of physical environment attained its present status wherein different components were added from time to time. Previously physical geography concerned with only three components i.e., lithosphere, hydrosphere and atmosphere but biosphere has been recently added to this disci pline. It is desirable that the historical development of four distinct branches of physical geogra phy e.g., geomorphology, oceanography, clima tology and biogeography should be discussed separately dealing with lithosphere, hydrosphere, atmosphere and biosphere respectively.
1.3.1 Geomorphology
Geomorphology is a significant branch of physical geography. The term of geomorphology stems from three Greek words i.e., ge (meaning earth), morphe (meaning form) and logos (mean ing discourse). 'Geomophology may be defined as the scientific study of surface features of the earth's surface involving interpretative descrip tion of landforms, their origin and development and nature and mechanism of geomorphological processes which evolve the landforms' (Savindra Singh, 1998)
The subject matter of geomorphology is organized on the bases of (1) dimension and scale of relief features (landforms), (ii) processes that shape the landforms, and (iii) the approaches to the geomorphic studies. 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 of the earth's crust (rocks) and partly on the forces coming from within the earth. Certain principles of structural and dynamic geology are included in geomorphic studies.
Theoretical geology helps in understanding the nature of landforms and, therefore, the origin of different types of reliefs like mountains, plateaus, faults, folds, continents and ocean ba sins cannot be properly understood because it helps in understanding the denudational landforms which develop on them.
1.3.2 Oceanography
The science of oceans i.e., oceanography includes marine geology, marine geomorphology, physical oceanography, chemistry of ocean water and bio-oceanography. The origin of ocean basins (continental drift and seafloor spreading), struc ture of crust and mantle, characteristics of ocean deposits and characteristics and origin of marine landforms are studied in marine geology and geomorphology.
Physical oceanography includes the consideration of physical properties of ocean water (e.g. temperature, pressure, salinity, den sity, compressibility, viscosity, water masses and their distributional patterns) and dynamics of ocean water (e.g. sea waves, currents, tides, tsunamis etc.). Recently, marine meteorology is also included in oceanography wherein atmos pheric conditions over ocean water are studied. Bio-oceanography includes the study of the char acteristics, evolution, distribution and dispersal of marine organisms.