I42 CRA CORON: 
continental borders, if not of all land surfaces, are known to be 
of common occurrence. 
Rapid submergence of a peneplain would undoubtedly result in 
the formation of a sea bottom of small relief with a general seaward 
slope; but it is impossible to imagine a peneplain the level surface 
of which would, in the period preceding submergence, end abruptly 
at the shore line with a sharp transition to a steep slope into the 
adjacent ocean basin. Even if such a state of affairs were possible, 
it would be necessary, in order to account for the formation of the 
Fic. 2.—Diagrams copied from those used by Gardiner to illustrate theories of 
shelf formation, with additions showing the development by deposition of a profile 
of equilibrium. 
continental shelf in this manner, to postulate a submergence of all 
the continental margins to the same extent, about 600 feet, and in 
most cases to disregard entirely the evidence afforded by the geo- 
morphology of coastal lands as to their erosional and deformational 
history. A submerged peneplain could not be expected to provide, 
ready made, a graded subaqueous shore profile. Upon an initial 
surface so formed wave action would immediately come into opera- 
tion, cutting in some places and depositing in others; and so, even 
if the initial form of any part of the continental shelf may have been 
a submerged peneplain, the sequential form which the shelf exhibits 
today must be ascribed to the work of waves. 
The development of a peneplain, moreover, necessitates a very 
long period of erosion, during which the land mass on which it 1s 
