PHYSICAL GEOGRAPHY OF THE PLEISTOCENE 267 



4. In the West Indies and Central America, the interpretation 

 of facts and supposed facts seems to be more or less uncertain. 

 Spencer would make the amount of change of level in the West 

 Indies within this general period very great, even 8,000 to 11,000 

 feet higher than now. Hill would have some portions of Cuba at 

 least 2,000 feet higher than now at or since the close of the Tertiary, 

 and the Barbadoes 1,100 feet higher at about the same time, while 

 Hershey thinks the Isthmus of Panama has been bowed up 1,000 

 feet or so since the beginning of the Pleistocene. 



If even the more moderate of these figures are correct, it appears 

 that the average relative increase in the altitude of the continent 

 must have amounted to several hundred feet at least. This amount of 

 elevation must have been adequate (i) to increase erosion by streams 

 greatly, this increase resulting both from (a) increase in precipitation, 

 and {b) increase in gradient of the streams; (2) to lower in some slight 

 measure at least the average temperature of the land, and to increase 

 its range; and (3) to reduce the amount of vegetation on the average, 

 both because of {a) the unfavorable change in temperature and {h) the 

 more rapid erosion. 



Outside of North America, similar changes seem to have been 

 in progress. Thus in South America, such determinations as are 

 at hand point to an elevation approaching 3,000 feet at a maximum 

 on the west coast of South America, since the late Tertiary. Changes 

 of similar import, and perhaps -of comparable extent, are indicated 

 by the facts reported from other continents, though for all but Europe, 

 the facts are meager. In Europe, changes of level at the close of the 

 Tertiary were not everywhere great, but about the borders of the Alps, 

 the increase of elevation is estimated by Penck and Bruckner to have 

 been 300 to 500 meters. 



It should be noted that the deformations of this time were more 

 important in affecting the height of the land than in affecting its area. 

 Yet from the evidence of existing floras and faunas, it seems probable 

 that the up-swelling of the contiguous parts of America and Asia were 

 suflicient to connect them by way of the Aleutian Islands. Shaler 

 and Spencer have urged reasons for thinking that Florida and Cuba 

 were connected in the late Pliocene or early Pleistocene, but this con- 

 clusion cannot be said to be established. In Europe, within the same 



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