01 February 1985
Vol 227, Issue 4686

About The Cover

Variegated Glacier (Alaska) in full surge, 4 July 1983. View is upstream from a point 5 kilometers from the terminus. It shows the extreme fracturing (crevassing) and bulging, or arching up, of the ice caused by the surge. Ice in the middle ground is moving toward the camera at a speed of about 30 meters per day. In the foreground is a lake (with icebergs) formed by welling up of highly turbid (brown) water in the large crevass (left foreground), from which the water flows out to the glacier margin. This water comes from the glacier bed and its upwelling is an indication of high pressure in the basal system. See page 469. [Elise Mezger, California Institute of Technology, Pasadena 91125]