The denuded mountain slopes and plateaus of southern Mexico are due to the prehistoric inhabitants who cleared away the tropical forest for their Indian corn fields, and then left them to the erosive action of the tropical rains and subsequent occupation by coarse grasses.
Furthermore, appropriate therapy, Eg allopurinol should theoretically prevent the development of chronic erosive arthritis.
Sediment supply, relative to fluvial transport capacity, has therefore a potentially decisive effect on the erosive power of any bedrock river.
That a rapid subsidence did take place from the higher level is indicated by the fact that between it and the present level there is an absence of indications of erosive energy.
Much discussion has arisen as to their mode of origin, but it is probable they were caused by the erosive action of ice, since glaciers occupied the glens where they occur and wore down the rocks along the sides and bottom; but it is a point of difficulty in this theory whether ice could have eroded the deepest of the hollows.