EARTH SURFACE PROCESSES AND LANDFORMS, VOL. zyxw 16, 563-569 (1991) zyxw SHORT COMMUNICATION ROCK RESISTANCE TO EROSION: SOME FURTHER CONSIDERATIONS PAUL zyxwvutsr C. AUGUSTINUS University of Tasmania, zyxwvut P.O. Box 1214, Launceston, Tasmania 7250, Australia Received 4 December 1990 Revised 6 March 1991 ABSTRACT Rock resistance to erosion is an often described factor in geomorphic studies, and is generally considered to strongly influence the shape of erosional landforms. However, the property of the rock mass that enables it to resist erosion is rarely considered, and its measurement is rarely justified and assessed adequately. Allison (1988, 1990) examined the intact strength properties of several types of carbonate rocks and considered that dynamic Young’s modulus is a good indicator of rock material strength for geomorphic purposes, and cast doubts on the reliability of Schmidt hammer tests for this purpose. Alternative approaches to rock characterization from the view point of evaluating rock intact strength are considered. zyxwvuts KEY WORDS Rock strength Erosion resistance Young’s modulus Schmidt hammer INTRODUCTION Allison (1990) argued that field and laboratory determination of limestone dynamic elastic moduli using a non-destructive ultrasonic apparatus confirms its use as a technique for indirectly determining rock strength. Further, it was argued that samples which have undergone no preparation prior to testing give results which are more accurate than data collected using the Schmidt hammer; and finally that the elastic properties of materials appear to be a better indicator of resistance to erosion that rock strength. The veracity of each of the assertions will be assessed and some alternative interpretations and im- provements in the method are proposed here. ROCK RESISTANCE TO EROSION Rock resistance to erosion is an often described, but rarely defined topic in the literature. A large body of literature exists from the view point of assessing rock wear properties and mass strength for civil engineering purposes (i.e. Deere and Miller, 1966; Stacey, 1973; Szlavin, 1974; Abdulatif and Cruden, 1983; Gunsallus and Kulhawy, 1984), but the concepts has not been adequately assessed for usage in a geomorphological context. The concept of rock resistance to erosion must refer to the ability or otherwise of the rock in question to resist the degrading effects of the acting erosion process. The type of erosion process being considered will have its ability to modify the rock surface on which it is operating controlled by any one or a combination of several rock mass index and intact strength properties. Choosing the relevant rock strength property for the study at hand will depend on the mechanics of the particular erosion process, as well as its scale and rate of operation. For example, in a glaciated terrain of massively jointed high strength bedrock, it is reasonable to assume that the subglacial abrasion process will be a quantitatively more important component of glacial erosion 0 197-933 7/9 1 /0605634)7$05.Oo zyxwvut 0 1991 by John Wiley zyxwvuts & Sons, Ltd.