98 REVIEWS 



''Features of Karakoram Glaciers Connected with Pressure, 

 Especially of Affluents." By William H. Workman. Zcit- 

 sckriftfiir Gletsckerkunde, Bd. 8, 1913. Pp. 40. pi. 1. 

 Great relief, numerous large, high snow-fields, and a series of long, 

 branching valleys reaching down from the uplands furnish the conditions 

 in the Karakoram Mountains for a ramifying system of glaciers that 

 exhibits phenomena lacking in most valley glaciers. The phenomena 

 are chiefly connected with pressure, particularly that developed by 

 affluent glaciers where they press down on their mains. The tremendous 

 force of the tributary glacier, directed essentially at right angles to the 

 direction of movement of the main glacier, forces the latter aside, but 

 the affluent is shortly bent downward and moves parallel to the other 

 glacier. The two glaciers crowd upon one another and are individually 

 somewhat squeezed together, but they remain perfectly distinct, in some 

 instances to a distance of 50 or 60 km. below the point of junction. Of 

 particular interest is the union of the Siachen Glacier (4.4 km. wide, 

 40 km. long above this junction) and Tarim Shehr (3 km. wide, 25 km. 

 long") which meet at an angle of about 140 . With much structural 

 disturbance and a partial displacement of the main glacier, Tarim 

 Shehr turns through 140 around a small promontory before it moves 

 parallel to the main. Where the valleys are constricted the glaciers 

 are notably narrowed, and the white ice tongues may completely dis- 

 appear; but the glaciers do not spread to fill the wide parts of the valley. 

 Where the pressure of affluents on the main glacier is very great, 

 the ice surface, especially along moraine-covered belts, is thrown up 

 into rather irregular-shaped hillocks. Below the juncture of the two ice 

 masses the hillocks become more pronounced, they are covered with 

 piles of discrete debris, and become more or less united in a band parallel 

 to the direction of ice movement; they are then termed "hillock mo- 

 raines." Individual hillocks vary from 10 m. to 70 m. (exceptionally 

 150 m.) in height above the rest of the glacier. The moraine shows 

 no evidence of having been pushed up from below or formed simply by 

 differential melting. Transverse to the direction of pressure, white ice 

 exhibits a series of long parallel ridges. Seracs have developed where 

 there is a steepening of the gradient of the glacier beds, where the ice of 

 Tarim Shehr impinges upon a plowlike promontory, and where con- 

 striction of the valley causes longitudinal crevassing. It is concluded 

 that differential melting is an important agent in increasing the height 

 of moraine-covered belts down the glacier. Vertical bands parallel to 

 the direction of movement of the ice are to be noted in all the glaciers; 



