DIASTROPHISM AND THE FORMATIVE PROCESSES 399 
23. The data assembled by Rollin Chamberlin’ imply that 
prolonged loading and unloading are either (a) sufficient to cause 
diastrophism at long intervals, or else (b) act as triggers to set off 
other forces that were steadily accumulating during the quiescent 
periods. Whether loading and unloading are in themselves suff- 
cient causes of deformation or not is a question on which studies in 
megadiastrophism are expected to shed decisive light. 
THE TOTAL AMOUNT OF SELF-COMPRESSION OF THE EARTH 
24. In spite of the foregoing conservative considerations, the 
amount of unequivocal deformation shown in Paleozoic and later 
strata alone is so large as to overtax all resources of diastrophism 
safely assignable to the cooling of the earth, and yet the very com- 
plex diastrophism of the earlier areas greatly exceeded this later 
diastrophism. The deformations since the middle of the Miocene 
are so great—ain view of their lateness in the history of the earth— 
as to suggest that the causes of diastrophism are very persistent 
and very profound. 
25. If we try to measure the total diastrophism by comparison 
with the total life-evolution, a result more than ten times that of 
the Paleozoic and later ages is implied, for diastrophism should 
have been very active in the formative ages and declined afterward, 
while life-evolution appears to have been accelerated as time 
went on. 
26. If the intimate crumpling, close folding, and faulting of 
the Archean and Proterozoic terranes is made the basis of estimate, 
the total diastrophism must have been very great, but just how 
great it is impossible now to say. 
27. If the present continents be looked upon as the outcome of 
a contest between sea-shelf outbuilding, on the one side, and 
inthrust from the oceans, on the other, the total diastrophism is 
clearly large, but very difficult to estimate definitely. 
28. If the early earth be supposed to have been segmented 
‘in a natural mechanical way, and the existing continents and 
ocean basins interpreted as derivatives from these segments by 
t“Periodicity of Paleozoic Orogenic Movements,” Article VII, Jour. Geol., 
‘Vol. XXII (1914), pp. 315-45. 
