GRAVEL AS A RESISTANT ROCK? 
SIDNEY PAIGE 
U.S. Geological Survey 
In a recent? number of the Journal of Geology, Mr. John L. 
Rich presents the thesis that “gravel, in its relation to the agencies of 
denudation, is under certain geological conditions a highly resistant 
rock. To these agencies it will, in general, offer greater resistance 
than ordinary igneous or sedimentary rocks, with a few possible 
exceptions.’’3 
The writer is in accord with this general thesis; but the specific 
evidence presented in arriving at this conclusion is not wholly 
accurate, and certain deductions affecting the physiographic 
history of the region should in the writer’s opinion be interpreted 
differently. 
Mr. Rich divides his paper into three parts: (1) to point out the 
theoretical reasons for the resistant nature of gravel deposits; 
(2) to show, from an actual occurrence in nature, that the gravels 
do behave as the theoretical considerations would lead us to expect; 
and (3) to sketch by way of suggestion the normal course of develop- 
ment of topography in a region where alluvial fans of coarse material 
are accumulating at the base of mountains. It is especially with 
No. 2 that the following has to deal. 
It is shown that a plain-like lowland lies between the northern 
edge of the gravel deposits and the high mountains to the north. 
This lowland is in places too feet below the base of the gravel south 
of it, and is crossed by the mountain streams flowing southward 
out upon the desert deposits. 
To explain this feature Mr. Rich presents three alternative 
hypotheses: (1) The gravels may have been removed by erosion 
t Jour. Geol., XIX, No. 6. 
2 Op. cit., Pp. 492. 
3 Published by permission of the Director of the U.S. Geological Survey. 
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