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Geographical Cycle of Davies William Morris Davies was an american geographer who gave first general theory on landform development.. Davis' most influential scientific contribution was the "geographical cycle",  which he defined in an article,’ The Rivers and Valleys of Pennsylvania ,’ published at the end of 19th century. According to him, uplifted landmass undergoes sequential development or erosion till base level in various stages.This sequential development referred as cycle of erosion. FUNDAMENTAL PRINCIPLES 1.Cyclic nature of landform evolution. 2 Uniformitarianism:The same physical processes and laws that operate today, operated throughout geologic time, although not necessarily always with the same intensity as now BASIC POSTULATES Upliftment takes place on featureless plain which he modified 10 yrs later to accept it can occur from geosyncline. Upliftment on geological timescale is sudden.In later works, he accepted it to be episodic. ...

Q. Explain the concept of Isostasy as postulated by Airy and Pratt Isostasy refers to mechanical stability that exist between all the high lying features like mountains and low lying features like ocean basin on fast rotating earth. Sir George Airy’s theory Airy adopted Edward Suess Scheme of earth’s interior structure and assumed that it is made up of three layered structure- Sial,Sima and Nife. Sial is uppermost layer containing crust with density of 2.67 and Sima with density of 3.0.Since, Sima is denser, semi molten and just below sial, sial is floating on sima. REASON FOR ISOSTASY Sial can be imagined to be divided into vertical sections containing mountains,plateaus,plain,ocean basin,etc separately.. Section with higher feature like mountain has deeper root while section with lower feature has shallow root.Though, same density of all the sections . This arrangement is mechanically stable due to principle of flotation. Airy demonstrated this th...

Q.Write short note on seafloor spreading theory (08/20) Concept of seafloor spreading was given by Harry Hess in his work titled ‘Essays in Geo-poetry’ published in 1960s. He connected his findings related to mid-atlantic ridge(using sonar technology) and convectional current theory to arrive at his theory of seafloor spreading which talks about horizontal movement of ocean floor. CONVEYOR BELT MECHANISM Rising limb of conventional current lies below the continental ridges.This rising plumes spreads below the ridge providing tensional stress and a driving force for the parallel movement of ocean floor away from the ridge.Some of these rising magma comes out of the ridge and spreads itself on the both side of ridge.This results in creation of fresh layer of ocean floor. Thus, ocean floor is being created at the oceanic ridge such that the younger layer lies near ridge and older away from it.Thus, oceanic basin was estimated to be not older than 200 millions ye...

Q.Critically evaluate the continental drift hypothesis of A.Wegner Q. Bring out distinctions between the continental drift theory and the plate tectonic theory. Q. Discuss the limitations of the theory of continental drift and show how the theory of plate tectonics is an improvement over it. This theory marks departure in previously hold notion that continents are static and mountains are wrinkles in the crust.                 Though concept of drift of continents was given earlier too, but the full fledged theory which stirred the imagination of scholars worldwide is attributed to Alfred Wegner of germany who gave his theory in 1912. ASSUMPTIONS Earth interior is made of 3 layers : sial,sima and nife (Edward Suess Scheme) Continental crust is made of sial and is less denser than sima which lies just below it. Continental crust is floating over sima.oceanic crust is uppe...