Denudation of the Continents

ESTIMATES of denudation often enter into geologic argument and have to be extrapolated backwards over geological intervals of time. The importance of human activity in the present-day erosional cycle has been pointed out by Douglas¹ and has been carefully evaluated by Judson² in a comparison of world-wide river load estimates with data from the nearly undisturbed Congo and Amazon basins. Judson concludes that man's intervention has increased the overall denudation rate from 9 to 24 billion tons a year: far more than enough to discredit the present rate as a geologic parameter. In this communication I attempt to verify Judson's pre-human estimate and to defend its general applicability to the past 300 million years.