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There is constantly erosion of soils and rocks, producing materials which are transported by flowing water. Fluid flow is the chief erosive agent, and there will be more or less erosion according to the severity of the climate, the steepness of the slope, the lithology of the outcrops of rock and the regional and biogeographical tectonic activity (vegetation cover, human action). Chemical weathering of rocks removes a certain number of elements in solution, leaving behind loose materials which may be removed by mechanical erosion in water. Studies of solids transported in rivers link mechanical erosion and erosion of the dissolved materials with chemical erosion, given some corrections. The lowest figures obtained for the progress of atmospheric change on crystalline rocks are 0.3 to 3 cm per 1000 years in a temperate zone and 4 to 7 cm per 1000 years in a tropical zone. As a general rule erosion speeds are divided into two sets of values, associated with plain and hill morphology and with mountain morphology. In any climate other than a periglacial one, both sets are centred on median values of 50 mm to 500 mm per 1000 years for hardened rocks and for plains and hilly areas and mountainous areas, while for unconsolidated rocks or periglacial climates these values have to be multiplied by a factor of 10.

Additional information

Authors: AFZALI H, BRGM, Orléans (FR);FOURNIGUET J, BRGM, Orléans (FR);PEAUDECERF P, BRGM, Orléans (FR)
Bibliographic Reference: EUR 12503 FR (1990) Volume 1, 37 pp., FS, ECU 5
Availability: (2)
ISBN: ISBN 92-826-1008-X
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