Correspondence — Mr. Warren TJpham. 331 



The disturbances along this belt, however, have been of a diifei'ent 

 order from the uplifts and subsidences which have affected the 

 whole continental area northward from, the Gulf of Mexico, as 

 known by the Pleistocene submergence of river valleys and fjords 

 on the Atlantic, Pacific, and Arctic shores of North America, No 

 less than twenty submerged, valleys, some of them extending to 

 depths of 2000 to 3000 feet, have been found by soundings on the 

 coast of California by Prof. George Davidson, of the U.S. Coast 

 Survey; and Prof. Joseph Le Conte has shown that the time of 

 elevation during which they were eroded was the Pliocene and early 

 Quaternary, which also included the plication of the Coast Range, 

 the outpouring of the lavas forming the Cascade Range, and the fault- 

 ing and tilting that elevated the Sierra Nevada, Wahsatch, and. Basia 

 Ranges to their present height (Elements of Geology, new ed. 1891 ; 

 Bulletin G.S.A. vol. ii. 1891, pp. 323-330). On the Atlantic coast, 

 too, the submerged valleys mentioned in previous articles were 

 doubtless eroded during the same time. Excellent evidence of this 

 is given by the submarine channel of the Hudson, partly a profound 

 fjord, extending about 100 miles beneath the sea, and descending to 

 the depth of 2844 feet ; for samples of its bottom and banks, 

 brought up by the sounding-lead, appear to belong to a continuation 

 of the Tertiary sandy clays of New Jersey (Am. Jour. Sci. III. 

 vol. xxix. pp. 475-480, June, 1885 ; vol. xl. pp. 425-437, Dec. 1890, 

 with map). These deeply submerged, narrow river channels, and 

 the similar Arctic fjords, together bear testimony of a late Tertiary 

 and early Quaternary elevation of nearly all of North America to 

 such altitude that the resulting colder climate would induce glaciation. 

 So widely extended continental uplifting, and the later Pleistocene 

 depression of the same area, belong to a class of the earth's crustal 

 movements which Gilbert and White have called epirogenic, that is, 

 continent-making, in contrast with orogenic or mountain-making 

 upheaval and subsidence. 



In the Caribbean region depressions succeeded by elevation during 

 the Quaternaiy era, which are known from the raised coral reefs 

 studied by Mr. Jukes-Browne and others, belong to orogenic move- 

 ments, chiefly by faulting, uplifting, and tilting, which have taken 

 place on a most grand scale in this era throughout the chain of the 

 West Indies and Windward Islands, and along the entire Cordilleran 

 belt from Cape Horn to Panama, to the Sierra Nevada and Great 

 Basin, and to Mount St. Elias and the Aleutian Islands. These 

 mountain-making disturbances have been closely related with the 

 great epirogenic uplift and depression of North America, and with 

 their duplication in two distinct Glacial epochs, divided by a very 

 long interglacial epoch on this continent ; but to attempt discussion. 

 of details of their correlation, or to speculate upon the condition 

 of the earth's crust and interior permitting such changes of levels, 

 would require too much space for a letter. Some notice of these 

 matters will be found, respectively, in my article in the American 

 Journal of Science for January, 1891, and in my appendix of 

 Wright's " Ice Age in North America." 



SoMERTiLLE, Mass., A:pril Uh, 1891. Wabeen Upham. 



