224 THE JOURNAL OF GEOLOGY. 



consequent upon the prevailing structure. This is shown princi- 

 pally by the fact that large glaciers, such as the Agassiz and 

 Seward, follow lines of displacement ; in several instances, cas- 

 cades occur where glaciers cross faults. 



THE PIEDMONT ICE SHEET. ^ 



Area. — The Malaspina glacier extends with unbroken con- 

 tinuity from Yakutat bay 70 miles westward, and has an average 

 breadth of between 20 and 25 miles. Its area is approximately 

 1,500 square miles; or intermediate in extent between the area 

 of the State of Rhode Island and the area of the State of 

 Delaware. 



It is a vast, nearly horizontal plateau of ice. The general 

 elevation of its surface at a distance of five or six miles from 

 its outer border is about 1,500 feet. The central portion is free 

 from moraines or dirt of any kind, but is rough and broken by 

 thousands and tens of thousands of crevasses. Its surface, when 

 not concealed by moraines, is broadly undulating, and recalls the 

 appearance of the rolling prairie lands west of the Mississippi. 

 From the higher swells on its surface one may see for many 

 miles in all directions without observing a single object to 

 break the monotony of the frozen plain. So vast is the glacier 

 that, on looking down on it from elevations of two or three 

 thousand feet above its surface, its limits are beyond the reach 

 of vision. 



Lobes. — The glacier consists of three principal lobes, each of 

 which is practically the expansion of a large tributary ice stream. 

 The largest has an eastward flow, toward Yakutat bay, and is 

 supplied mainly by the Seward glacier. The next lobe to the 

 west, is the expanded terminus of the Agassiz glacier ; its cur- 

 rent is toward the southwest. The third great lobe lies between 

 the Chaix and Robinson hills, and its main supply of ice is from 

 the Tyndall and Guyot glaciers. Its central current is south- 



^ This account of the Malaspina glacier has been compiled principally from the 

 proof-sheets of a report by the writer on a second expedition to Mt. St. Elias in 1891, 

 to appear in the Thirteenth Ann. Rep. of the U. S. Geological Survey. 



