ABRASION BY GLACIERS, RIVERS, AND WAVES 
LEWIS G. WESTGATE 
Ohio Wesleyan University, Delaware, O. 
INTRODUCTION 
Erosion? or land sculpture includes rock disintegration, where the 
rock is coherent, and transportation of the material disintegrated. 
Disintegration has been divided into weathering and corrasion. 
Stream- and wave-wear may be either chemical or mechanical, though 
in all ordinary circumstances the mechanical wear is so much greater 
than chemical solution that the latter may be neglected. Ice-wear 
is purely mechanical. Omitting chemical solution, which is an 
entirely distinct process, corrasion may be defined as the mechanical 
wear performed by wind, streams, waves or glaciers. Gilbert? uses 
the term “‘corrasion,” excluding chemical corrasion, for the ‘‘mechani- 
cal wear .... performed by the aid of hard mineral fragments 
which are carried along by the current.”” Chamberlin and Salisbury 
define stream-corrasion as ‘“‘the wear effected by running water.’ 
This use of the term is wider than that of Gilbert, for it includes not 
only wear by tools, but also the process of sweeping away material 
which has always been incoherent and “ material loosened in advance 
by the process of weathering.” To distinguish these radically dif- 
ferent processes of stream-action, in this paper the term “abrasion”? 
will be used for the mechanical wear performed by tools, and “ pluck- 
ing” for the removal of rock fragments. ‘‘Corrasion,” including all 
mechanical wear by streams, will include both abrasion and plucking. 
None of the terms are new;. they have more or less overlapped in 
use, and it is believed that the meaning here assigned to them is that 
generally understood today. The terms can be applied to glacier- 
and wave-action with the same significance with which they are 
t Gilbert, Geology of the Henry Mountains, pp. 99-102. 
2 [bid., p. IO. 
3 Chamberlin and Salisbury, Geology, Vol. I, p. 113. 
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