Current chemical denudation, silicate mineral weathering and erosion in Irish catchments: reflections on the tortoise and the hare

Abstract

The denudation of any landscape occurs by both physical means (i.e. mechanical weathering and erosion) and also chemical means (i.e. dissolution of minerals). The rates of these different processes can vary greatly in both time and lithology. Herein we present the rates of physical weathering and also data on aluminosilicate and carbonate mineral weathering in a dozen Irish catchments using newly collected river geochemical data and previously published riverine suspended sediment information. Our carbonate denudation yields range from approximately 30 to 145 tons km-2 yr-1, while physical erosion yields are at least an order of magnitude less in most cases and silicate weathering yields are mostly <1 ton km-2 yr-1. Our analysis clearly demonstrates the importance of carbonate mineral dissolution in landscape lowering, supporting the notion previously put forward by Simms (2004a,b) of the analogy of the tortoise and the hare in geomorphologically shaping the surface of Ireland.