Temperature in Weathering

Abstract

From the shape of the earth, its axis angle of 23 1/2 °, its tilting, and its rotation around the sun, it is evident that there should be seasonal variations in weathering produced at different temperatures. Although there are differences caused by topography and other factors in any particular area (Fig. 4, Section 2-2), the following major facts cause the weathering in different zones: high average temperatures in moist regions increase vegetation and chemical weathering; high average temperatures in arid regions decrease vegetation, decrease chemical weathering, and promote mechanical disintegration; low average temperatures in moist regions cause permafrost and soil freezing, and slow down soil-forming processes generally—water movement is prevented or only occurs in a thin layer above the permafrost in summer; low average temperatures in dry regions produce maximum physical disintegration, and chemical weathering is either nonexistent or very slight. As well as regional climatic differences there are regimes of soil climates which are in part described as microclimates. Each soil has a particular climate within which the soil flora and fauna live, and within which chemical changes take place. The soil climate is dependent on the overall climate of the region, but it is modified by the material of the soil itself, whether sandy or clayey, light colored or dark, and by the water regime. The soil climate is responsible for the chemical environment of the weathering processes. Farmers producing crops have always known from observation about variations in soil temperatures, some fields being “warm,” others “cold.” In recent years two important books describing soil climates and microclimates have appeared: The Temperature Regime of Soils by A. M. Shul’lgin (translated from Russian by the Israel Program for Scientific Translations; 1965), and The Climate near the Ground by R. Geiger (Harvard University Press, 1965). There is now a wealth of information about the temperature in soils of the temperate zone, but not very much about tropical soil temperatures.