ANCIENT CLIMATES 4S5 



states bordering the Gulf of Mexico. There to-day many tropical mol- 

 luscan genera are found in the waters, and on the marginal coastal 

 plain there is a mixture of palms, deciduous trees and conifers. This 

 is just what we find in the fossil Eocene flora of California and Puget 

 Sound; laurels, figs, sycamores, chestnuts, elms, liquidambar, oaks, 

 palms and sequoias lived together. From this association we should 

 infer that the climate of the west coast was no longer tropical, but 

 subtropical, and very rainy. 



The middle Tertiary faunas are very like the present in the asso- 

 ciation of genera, and the flora on the land agrees with this. The palms 

 have disappeared, but laurels still occur. It is probable that the cli- 

 mate of the upper Miocene had about the same temperature as that of 

 the present in California, but it had, apparently, a much greater rain- 

 fall, or one much more evenly distributed. 



The Tertiary flora of the west coast was immensely richer than the 

 present. No elm, liquidambar, nor true laurel lives wild on the west 

 coast now, and many other types that flourished here are gone. The 

 impoverishment of the present tree flora of California, as compared 

 with that of the Tertiary, has been ascribed to volcanic activity, but 

 this is absurd. In the first place the great extinction of the old types 

 took place in the lowering of temperature near the end of Eocene time, 

 while the era of great lava outbursts on the west coast was after the 

 middle of the Miocene. The climate continued to cool off in the 

 Pliocene, as is shown by the northern types of mollusca that then ranged 

 as far south as Los Angeles, and by the freshwater lake deposits of 

 middle California, which contain a fauna at present confined to the 

 Klamath region of northern California and southern Oregon. The flora 

 of the Pliocene in California is very scanty, composed largely of willows, 

 alders and conifers, very much like that of the Olympic Peninsula in 

 Washington. 



The constantly decreasing temperature throughout the Tertiary is 

 sufficient to account for the reduction of the flora. The tropical and 

 finally the warm-temperate types were killed off locally, and such as 

 were confined to this region were wholly extinguished. Some of the 

 forms that lived in more favored regions to the south returned after 

 the Glacial epoch. But most of the region to the south of California 

 is not favorable to the extensive growth of forests, and many of the 

 types have never returned to California, except when brought in by man. 



In the early Quaternary there were extensive ice-sheets in the Sierra 

 Nevada, and probably the climate of the sea-coast was cool. The glaciers 

 came down the slopes to a line that is now about 3,500 feet above sea- 

 level; it is thought, however, that California stood considerably higher 

 than now, and that conditions here were more like those of the present 

 on the Olympic Peninsula. 



