A theoretical model coupling chemical weathering and physical erosion in landslide-dominated landscapes

Abstract

A current theory that links the uplift of the Himalayas to the drawdown of atmospheric CO 2 assumes that rates of chemical weathering are enhanced by accelerated physical erosion due to the increased exposure of fresh minerals. Although several studies have concluded that weathering rates do increase with erosion rates, there is disagreement over the form of that relationship. Some find a linear relationship between weathering rate and erosion rate; others, however, find that weathering is only approximately proportional to the square root of physical erosion such that changes in erosion rate are not matched by equivalent changes in weathering rate. Defining the nature of the relationship is critical because it determines the sensitivity of changes in weathering rate to changes in erosion rate. In this study, a theoretical model that couples erosion by landslides with chemical weathering processes was derived to explore the nature of this relationship in rapidly eroding landscapes. Results from the model suggest that, where landsliding is the dominant erosional process, the rate of chemical weathering is only proportional to the erosion rate raised to the ∼ 0.6 power. Therefore, even if weathering rate is wholly dependent on erosion rate, increases in erosion will not be matched by equivalent increases in chemical weathering.