Exogenous Process

Exogenous Process

 

a geological process caused by sources of energy exterior to the earth’s surface, chiefly solar radiation, in combination with the force of gravity.

Exogenous processes occur at or near the surface of the earth’s crust and are the mechanical and physicochemical interactions of the crust with the hydrosphere and atmosphere. They include weathering and the geological action of wind (eolian processes, deflation), flowing surface and groundwaters (erosion, denudation), lakes and swamps, the waters of the seas and oceans (abrasion), and glaciers (exaration). The most important manifestations of exogenous processes on the earth’s surface are the disintegration of rocks and chemical transformation of their constituent minerals (physical, chemical, and organic weathering), the removal and transport of the resulting loosened and soluble products by water, wind, and glaciers, and the deposition (accumulation) of these products in the form of sediments on land or at the bottom of water basins and their gradual transformation into sedimentary rocks (sedimentogenesis, diagenesis, catagenesis).

Exogenous processes, together with endogenous processes, contribute to the shaping of the earth’s relief and the formation of sedimentary rocks and associated ore deposits. Thus, for example, ores of aluminum (bauxites), iron, nickel, and other minerals form under conditions of weathering and sedimentation. The selective deposition of minerals by flowing waters results in the formation of gold and diamond placers. Combustible minerals form under conditions favorable to the accumulation of organic matter and sedimentary strata rich in such matter.

REFERENCES

Iakushova, A. F. Dinamicheskaia geologiia. Moscow, 1970.
Gorshkov, G. P., and A. F. Iakushova. Obshchaia geologiia, 3rd ed. Moscow, 1973.
Obshchaia geologiia. Moscow, 1974.

G. P. GORSHKOV and E. V. SHANTSER

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