Physical Geography

Composition of the Atmosphere

The Earth is surrounded by air—a mixture of various gases that reaches up to a height of many kilometers. This envelope of air makes up our atmosphere. It is held in place by the Earth’s gravity. Almost all the atmosphere (97 percent) lies within 30 km of the Earth’s surface. The upper limit of the …

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Dust Storm

Strong, turbulent winds blowing over barren surfaces can lift great quantities of fine dust into the air, forming a dense, high cloud called a dust storm. In semiarid grasslands, dust storms are generated where ground surfaces have been stripped of protective vegetation cover by cultivation or grazing. Strong winds cause soil particles and coarse sand …

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Stream Erosion

Streams erode in various ways, depending on the nature of the channel materials and the tools with which the current is armed. The flowing water drags on the bed and banks and also forces particles to hit the bed and banks. These actions easily erode alluvial materials, such as gravel, sand, silt, and clay. This …

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Lake

A lake is a body of standing water with an upper surface that is exposed to the atmosphere and does not have an appreciable gradient. Ponds, marshes, and swamps with standing water can all be included under the definition of a lake. Lakes receive water from streams, overland flow, and ground water, and so they …

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Plate Tectonics

The rigid lithospheric slabs are called plates. The study of the whole mechanism of evolution, nature and motions of plates, deformation within plates and interactions of plate margins with each other is collectively called as plate tectonics. Plate tectonic theory, a significant scientific advancement of the decade 1960’s is based on two major scientific concepts e.g. (1) the continental …

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Continental Drift Theory

The idea of lateral movement of continents or continental drift was put forward in 1912 by Alfred Wegener in a book ‘The Origin of Continents and Oceans’. The continental drift theory of Wegener ‘grew out of the need for explaining the major variations of climate in the past’. According to A. Wegener, The climatic changes which have occurred on the …

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Interior of the Earth

The interior of the Earth is divided into different layers and in many ways such as based on chemical composition or mechanical properties. Chemically, Earth’s interior is divided into the crust, mantle, and core. Mechanically, it can be divided into lithosphere, asthenosphere, mesosphere, and barysphere. Source of Information: Most of our knowledge about the interior of the earth is largely based on …

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Inversion of Temperature

Inversion of temperature occurs when warm air lies over cold air. Normally, temperature decreases with increasing altitude in the troposphere at an average rate of 6.5 °C per 100 meters but sometimes this normal trend of decrease of temperature with increasing heights is reversed under special circumstances i.e. temperature increases upward up to a few kilometers …

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Seafloor Spreading

Harry Hammond Hess propounded in his theory of seafloor spreading that the mid-oceanic ridges were situated on the rising thermal convection currents coming out from the mantle. The oceanic crust moves in opposite directions from mid-oceanic ridges. These molten lavas cool down and solidify to form new crust along the trailing ends of divergent plates. Thus, there is …

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Theory of Isostasy

Different relief features of varying magnitudes e.g. mountains, plateaus plains, lakes, seas, and oceans, faults, and rift valleys, etc. standing on the earth’s surface are probably balanced by certain definite principle, otherwise, this would have not been maintained in their present form. Whenever this balance is disturbed, there start violent earth movement and tectonic events. …

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