114 ALASKA GLACIERS 



HANGING VALLEYS 



Of the various classes of evidence from which the his- 

 tory of Pleistocene glaciation is inferred, the physiographic 

 is most available to observers who see the land chiefly from 

 the deck of a vessel. Ice-scoured surfaces referable to 

 the ancient glaciers were occasionally discovered during 

 our journey, and a few drift deposits were closely exam- 

 ined; but such observations served chiefly as checks on 

 inferences from topographic form. 



The general characters of the physiographic data which 

 may be used in such studies are familiar and need not be 

 recited here, but a special sculpture feature the hanging 

 valley may need introduction to some of my readers. 

 Its utility in the interpretation, discrimination and estima- 

 tion of the work of Pleistocene glaciers has been little 

 appreciated until quite recently, 1 but in the study of the 

 Alaska field it was found extremely useful. 



A hanging valley is a small U-valley tributary to a 

 larger valley, the floor of the smaller being considerably 

 higher at the junction than the floor of the larger. Many 

 of them are short, high-grade troughs, heading in cirques ; 

 some are mere cirques, without troughs spoon-bowl hol- 

 lows, high on the walls of main valleys. They are asso- 

 ciated with other evidences of glacial sculpture, and the 

 elevation of their floors is believed to result, as a rule, 



*Lake Chelan, bj Henry Gannett : Nat. Geog. Mag., vol. ix, pp. 417-428, 1897. 

 Glacial erosion in the valley of the Ticino, by W. M. Davis : Appalachia, vol. 

 ix, pp. 136-156, 1900. Glacial erosion in France, Switzerland and Norway, by 

 W. M. Davis: Proc. Boston Soc. Nat. Hist., vol. xxix, pp. 273-322, 1900. 

 Review of the last by T. C. Chamberlin : Jour. Geol., vol. vm, pp. 568-573, 

 1900. 



Davis's second paper reviews the literature, points out that McGee, De Lap- 

 parent and Richter had advanced somewhat similar ideas as to the origin of 

 hanging valleys before the appearance of Gannett's paper, and mentions an 

 unpublished address by Penck. The glacial explanation of the hanging valleys 

 of the Alps is opposed by Bonney and Garwood in Quart. Jour. Geol. Soc. 

 London, vol. LVIII, pp. 690-718, 1902. 



