Land Ice of Arctic axd Sub-Arctic Regions 39 



action, together with warping of the sea floor when raised up or 

 unequal sedimentation before elevation above sea level, may also 

 perform a significant part in the formation of ridges that eventually 

 act as barriers to land-locked bodies of water. It is probable the 

 changes of elevation along the coast that have raised and exposed 

 the coastal-plain ice-beds are due to the shifting of the loading point 

 areas of the rivers. None of the exposed ice beds in coastal-plain 

 deposits in Alaska are reported to exceed elevations over thirty or 

 forty feet above the sea level. 



Under the conditions of climate and vegetation that have existed 

 along the Arctic coast during the Recent period, ice-beds might be 

 formed in a manner similar to the apparently older elevated ice- 

 beds occurring in the Pleistocene lake areas. 



It does not appear that the ice beds along the Arctic coast of 

 Alaska have the continuous or extensive development Dall claims 

 for them, as shown on his map, plate iii, Bull. No. 84, U. S. Geol. 

 Survey, 1892 ; nor with the statement, quoted, from whaling cap- 

 tains, made in his report on " The Coal and Lignite of Alaska : " *^ 



" At a depth of two feet is a stratum of pure ice (not frozen soil) 

 of unknown depth. This formation extends, with occasional gaps, 

 north to Point Barrow, and thence east to Return Reef, where the 

 ice layer is about six feet above the level of the sea. It goes south 

 at least as far as Icy Cape without any decided break, and is found 

 in different localities as far south as Kotzebue Sound." 



Mr. F. C. Schrader, who travelled along the Arctic Alaska coast 

 from the mouth of Colville River to near Cape Lisburne in 1901 

 also dissents from the views expressed by Dall.^^ He says : " The 

 observations made by the writer, ^^■hile boating along the coast, lead 

 to the inference that the ground ice is not of so widespread occur- 

 rence as the above quotation indicates. Between the Colville and 

 Point Barrow the ice is possibly more or less continuous along the 

 coast, but of its inland extension we have little evidence. Even 

 along the coast it is not extensively exposed. Here long stretches 

 of the low tundra country are apparently underlain by rock or earthy 

 deposit." 



" Of the localities at which the ice was observed, the most im- 

 portant are Cape Halkett and Cape Simpson, at each of which it 

 seems to be practically continuous for a distance of several miles. 



*■ Seventeenth Ann. Rept. U. S. Geol. Survey, 1896, p. 855. 

 "A Reconnaissance in Northern Alaska in 1901. U. S. Geol. Survey. 1904. 

 Professional Paper No. 20, pp. 91-93. 



