J. E. Marr—The Work of Ice-Sheets. 151 



TIL — The Work of Tce-Sheets. 



By J. E. Mark, M.A., F.G.S., 



Fellow of St. John's Coll. Camb., University Lecturer in Geology. 



THE occupation of Britain by Ice-sheets in Pleistocene times has 

 been established by the researches of Sir A. Ramsay, Dr. J. 

 Geikie, Messrs. Peach and Home, Tiddeman, GoodchihJ, and others. 

 At the time that these inquirers made their observations, the very 

 complex nature of the phenomena of the Greenland ice-sheet was 

 hardly recognized, and many difficulties arose, upon w^hich consider- 

 able light is thrown by a knowledge of the work of a modern ice- 

 sheet. Under these circumstances it may be well to apply the 

 information gained in recent years, and published by the Commission 

 for Directing the Geological and Geographical Exploration of Green- 

 land ^ to the clearing up of some of these difficulties. 



A few remarks upon the nature of this continental ice, extracted 

 from the " Meddelelser," may not be out of place. 



The Greenland ice-sheet is stated to extend probably over an area 

 about three hundred and fifty times that of all the glaciers of the Alps 

 taken together, and it may be readily understood that the phenomena 

 j)resented by such a mass are very different from those of the small 

 glaciers so generally known. The difficulties of exploration of this 

 great continental ice-sheet are very great, and the arduous under- 

 takings of the Danish explorers must command univei'sal admiration. 



Owing to the cold polar current which bathes the eastern coast 

 of Greenland, an almost impenetrable mass of ice blocks the shores 

 between latitudes 60° and 69° N., and consequently our knowledge 

 of that portion of the country is slight. On the western coast, how- 

 ever, a more favourable set of conditions exists, and the exploration 

 of the ice-sheet has been undertaken from this side. The southern 

 part of the country, around Cape Farewell, is occupied by gigantic 

 glaciers, in the depressions between rugged mountains reaching 

 a height of about 7000 feet, the summits of which, according to the 

 observations of Herr Sylow, appear never to have been covered by 

 moving ice ; but north of the latitude of Julianehaab the ice-sheet is 

 encountered, and the numerous fjords which indent the coast to the 

 north of this are frequently barred at their inner terminations by 

 great ice-cliffs which form the ends of huge glaciers projecting like 

 tongues of ice from the ice-sheet of the interior into the valleys of 

 the coast-region. 



The confinement of the ice to the valleys in this region appears 

 to be due to the elevation of the mountains surrounding the littoral. 

 The country rises rapidly from the fringe of islets surrounding the 

 coast, which have a maximum height of under one thousand feet, to 

 heights of from 2000 to 4000 feet upon the peninsulas between the 

 fjords. After this it falls towards the interior of the fjords, and 

 again rises rapidly inland, so that one meets with summits of 3000 

 to 5000 feet and more, further inland ; but as the ice itself rises in 

 the interior, these heights become more and more buried in ice, 



^ " Meddelelser cm Gronland," parts i. — vi. Copenhagen, 1879 — 1883. 



