256 ANNUAL REPORT SMITHSONIAN INSTITUTION, 192 8 



worth ^ we learn that there are in western Peru three prominent 

 elevated marine terraces, the " tablazos " of the natives. These are 

 " a monument to the efficacy of marine erosion," and the account of 

 their making is one of the most interesting parts of the book. Dur- 

 ing the Pleistocene, he says, the Peruvian coast was " moved up- 

 ward and downward hundreds of feet again and again. The sea 

 advanced and retreated many times, cutting its cliffs into the land 

 10 miles or 20 miles on each occasion." 



In other places Wegener tells us that the line of separation where 

 the original continent split apart is not at the shore line but at the 

 upper edge of the continental slope or the outer edge of the shelf 

 seas, commonly placed at about 600 feet beneath the present sea level. 

 In many places this not-Avell-ascertained line is very different from 

 the shore line, but even so, what are the shelves if they are not the 

 fills and cuts of the sea storms and currents? Are we to believe, 

 with Wegener, that shore lines and shelf seas have remained con- 

 stant in shape, position, and contour during 120,000.000 years? 



WEGENER'S SEA MOVEMENTS AS PROOF OF POLAR WANDERING 



In Chapter VIII of his book Wegener argues for a viscous earth, 

 and says that if this is not true there could have been no crustal 

 movement or polar wandering. But in regard to the latter hypoth- 

 esis he says that polar wandering may actually be no more than 

 crustal movement, or, in other words, that the axis of the earth may 

 not change, but the crust only slips over the nucleus. However, he 

 adds, " presumably both occur," naniel}^, the poles move as well as 

 the crust (pp. 121-122). To prove these conclusions he presents two 

 greatly generalized maps showing transgressions and regressions 

 of the seas over Pangaea, and says that when the pole wanders to 

 the east it brings on in the Northern Hemisphere regression of the 

 seas to the east and transgressions in the west, and in the Southern 

 Hemisphere the water movements are reversed. 



He selects Devonian to Permian time to prove this " law," for 

 during these periods " the poles wandered rapidly." His map (his 

 fig. 22) giving the transgressions and regressions over Pangaea for 

 all Devonian and Lower Carboniferous time shows regression 

 throughout South America, Central America, and the whole of the 

 Appalachian geosyncline out to Newfoundland. Nothing is further 

 from the truth for the Americas during Devonian time, since this 

 is one of the periods of marked transgressions; during the Lower 

 Carboniferous, North x\merica also has wide transgression, but South 

 America has almost complete regression. He presents a like map (his 

 fig. 23) for all the time from Lower Carboniferous to upper Per- 



• Geology of the Tertiary and Quaternary Periods of the Northwest Part of Peru, Mac- 

 Millan, 1922. 



