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Soil is a complex and dynamic natural resource that forms the outermost layer of the Earth’s crust. It serves as a reservoir of minerals, organic matter, water, air, and living organisms. Soil also acts as a medium for the filtration and breakdown of injurious wastes. It also helps in the cycling of carbon and other elements through the global ecosystem. The formation of soil is a result of the weathering […]

The rate at which a rock weathers depends on the following factors. The particle size influences the rate of weathering. The smaller the particles, the greater the surface area for chemical attack. The mineral composition of a rock is also very important. The slate which is mainly composed of clay minerals is very resistant to weathering, while this is not true for marble. The order in which the silicate minerals […]

Weathering is the breakage and detachment of the sediments, particles, and granules from the surface of rocks. Weathering is a continuous and regular process, which is composed of many underlying processes, which are directly concerned with weathering. Weathering: The rocks break and undergo decay under the influence of atmospheric agencies like wind, sun, frost, water, and organisms, and produce soil. This phenomenon is called weathering. Weathering and Erosion together lower […]

What is the Theory of Seafloor Spreading? The theory of seafloor spreading was first proposed by Harold Hemmond Hess in 1960. the two fundamental facts that led him to postulate theory are: (i) the mid-ocean ridge occurs in all major ocean basins, and (ii) the oceanic crust has a thickness of 6 to 7 kilometers only whereas the typical thickness of continental crust is 30-40 km. Hess postulated that the […]

The flow of high heat associated with oceanic ridges proves the existence of “Convection Currents in the Mantle”. These currents are believed to be responsible for the movement of crustal plates. The idea of convection currents was first suggested by a British geologist A. Holmes in 1927 when he tried to explain the driving mechanism for continental drift. Holmes proposed that sub-crustal convection currents dragged the two halves of the […]

The theory of Plate Tectonics has evolved from Harry Hess’s concept of “seafloor spreading”. He proposed this concept in the early 1960s. Hess’s hypothesis was accepted when Vine and Mathews used it in explaining linear magnetic anomalies of the ocean basins. In 1967, W. J. Morgan, and J. T. Wilson extended the idea of Hess and produced the theory of plate tectonics. The factors, which led to the theory of […]

The theory of continental drift was presented by a German geologist, Alfred Wegener in 1910. He suggested that at the beginning of the Mesozoic era (200 million years ago), all the continents of the earth were united together. These continents were united to form a single supercontinent, which he called “Pangaea”. The huge ocean, that surrounded it, he called “Panthalassa”. Wegener proposed that this vast continent began to break up into […]

Isostasy C.E Dutton, in 1889, suggested that a gravitational balance exists between the elevated masses (i.e. continents) and ocean basin of the earth’s crust. It is believed that the lithosphere floats on the top of the partially molten substratum (asthenosphere) much like logs float on water. Mountains stand high because they are composed of rocks of low density, and ocean basins are low because they are made up of rocks […]

The mantle is a layered part of the earth, which is located just beneath the crustal layer of the earth. The Earth’s crustal surface (lithosphere) rides atop the asthenosphere. The asthenosphere is the upper layer of the Earth’s mantle, in which there is relatively low resistance to plastic flow and convection is thought to occur. While the lower part of the mantle is very hot and molten. Mantle convection means the movement […]

The knowledge about the interior structure and composition of the earth has a long history. Before seismic tomography, scientists knew very little about the interior of the earth. The study of the passage of seismic waves through the earth has helped in knowing the structure of the earth’s interior and in defining the physical properties of various layers. The seismic waves travel at different velocities depending on the nature of […]