532 RALPH ARNOLD 
correlation on a basis of diastrophism, unsupported by paleontologic 
evidence, is extremely hazardous. 
CYCLES OF DIASTROPHISM 
The period of the Tertiary uplift of the last worldwide cycle of 
diastrophism has been marked by two complete subcycles in the 
Pacific Coast of North America. The first was begun with gradual 
submergence in early Eocene, was continued by a gradual elevation 
in the later Eocene when marine conditions gave place to brackish- 
or freshwater conditions, and was completed by the epoch of uplift 
and erosion in the Oligocene. ‘The second was initiated by submer- 
gence in the Miocene, was continued by the gradual elevation in the 
Pliocene, when, as in the later Eocene, freshwater conditions sup- 
planted marine, and has been practically completed by the Quaternary 
uplift which marks the present position of the continent. 
PERIODS OF MAXIMUM ELEVATION AND SUBSIDENCE 
The periods of marked elevation were the Oligocene, late Plio- 
cene, and Quaternary; the periods of maximum subsidence were the 
middle Eocene and upper Miocene; the periods of greatest volcanic 
activity were the middle Eocene and the middle Miocene. It is note- 
worthy that the periods of maximum volcanic activity were practically 
coincident with the periods of maximum subsidence in adjacent 
areas. 
CHANGES IN CLIMATE 
The climate was tropical to subtropical in the Eocene, transitional 
from this to warm temperate in the Oligocene, warm temperate in the 
Miocene, transitional from this to sub-boreal in the lower Pliocene, 
sub-boreal in the upper Pliocene and lower Pleistocene, and warm 
temperate in the later Pleistocene. 
DIASTROPHIC PROVINCES 
The study of the Tertiary history of the Pacific Coast shows the 
following positive elements or areas of persistent uplift in the coastal 
belt: —The Olympic Mountains; a more or less uncertain, probably 
disconnected, belt along the western part of Washington and Oregon; 
the region of the California-Oregon line and thence eastward toward 
the Blue Mountains of southeastern Washington; the Santa Lucia 
Range, south of Monterey Bay; the region north and northeast of 
