Page 103 - Sedimentology and Stratigraphy

90 Continents: Sources of Sediment

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Fig. 6.3 The present-day world climate belts.

surface and in the soil profile. Weathering is the areas that regularly fluctuate around 08C, such as
breakdown and alteration of bedrock by mechanical high mountains in temperate climates and in polar
and chemical processes that create a regolith (layer regions (Fig. 6.5).
of loose material), which is then available for trans-
port away from the site (Fig. 6.1).
Salt growth
Seawater or other water containing dissolved salts
6.4.1 Physical weathering may also penetrate into cracks, especially in coastal
areas. Upon evaporation of the water, salt crystals
These are processes that break the solid rock into form and their growth generates localised, but
pieces and may separate the different minerals with- significant, forces that can further open cracks in
out involving any chemical reactions. The most the rock.
important agents in this process are as follows.
Temperature changes
Freeze–thaw action
Changes in temperature probably play a role in the
Water entering cracks in rock expands upon freezing, physical breakdown of rock. Rapid changes in tempera-
forcing the cracks to widen; this process is also known ture occur in some desert areas where the temperature
as frost shattering and it is extremely effective in can fluctuate by several tens of degrees Celsius between