DIASTROPHISM AND THE FORMATIVE PROCESSES 585 
own. While I think its molecular methods are distinctly different 
from those of a true plastic body, the result is a continental spread- 
ing out and flattening down whose aspect is almost identical with 
that of a plastic body. A block of asphaltum will spread and 
flatten for years but it finally reaches a state beyond which the 
movement will not go. It reaches a base-level of a certain sort. 
So the continents, under the action of glacier-like creep, however 
great its efficiency may be supposed to be, will merely flatten out 
to a certain extent and the resulting surface will ideally be of the 
nature of a sloping plain closely analogous to the peneplain produced 
by erosive degradation. 
So far as creep may be supposed to affect the continental shelf 
it moves it outward and slightly downward, and this fits the shelf 
surface for the reception of more sediments. If the downward 
component of the movement were greatly in excess of the rate 
of sedimentation, it would carry the shelf out of good working 
adjustment, much as in the case of ordinary diastrophism, but it 
seems highly improbable that the creep movement depresses the 
surface of the continental shelf faster than sedimentation naturally 
builds it up, even when the general continental creep is supple- 
mented by the special creep in the soft sediments of which the 
younger upper and outer portions of the shelf are formed. The 
work of creep in thus pushing the shelf outward and slightly down- 
ward relieves wave-action of a part of its burden in building out 
the shelf and so enhances the joint effect. It seems safe therefore 
to regard creep as a co-operating adjunct to both parts of the grada- 
tional work, the leveling of the lands and the building-out of the 
shelves. 
The outward creep of the continents reduces the capacity of 
the ocean basins and thus aids in lifting the sea-level and forcing 
the waters to creep out upon the lowered land. In this way also 
it co-operates with erosive gradation, which by transferring a 
portion of the land to the sea in another way raises the sea-level 
and causes its advance on the land. 
While the great sea-transgressions—and the great terranes of 
parallel strata to which they gave rise—imply a relative freedom 
from diastrophism while forming, the details of bedding and 
