The well-conceived and nicely executed British plans for measurement of velocity distribution along a vertical profile in the JungfraufirnReference Perutz ^{1 ,} Reference Gerrard, Perutz and Roch ² provided inspiration and guidance for a similar experiment in the Malaspina Glacier, Alaska. A repetition of the earlier experiment seemed desirable because it was not entirely certain that the Jungfraufirn provides the best conditions for extrusion flow,Reference Demorest ^{3 ,} Reference Demorest ⁴ the concept it was desired to test. The Malaspina Glacier appears to offer conditions ideally suited for extrusion flow. It is a piedmont glacier, a sheet of ice with gentle surface slope, covering more than moo square miles on the flit coastal plain of southern Alaska. From seismic reflections, the glacier’s floor is known to slope northward toward the mountains in opposition to the southward flow of ice.

In the summer of 1951 a vertical hole approximately 5 cm. in diameter was bored to a depth of 305 meters near the center of the glacier by an electrically heated hot-point. Boring stopped at this point because the hot-point ceased to function. The glacier at this point is 595 meters thick, its surface slopes southward at 6.6 meters per kilometer, and its floor, 183 meters below sea level, slopes gently northward. The bore hole was cased with aluminum pipe, 3.5 cm. inner diameter and 4 cm. outer diameter.

Orientation of the pipe was determined by a small-diameter inclinometer, kindly loaned free of charge by the Parsons Survey Company of South Gate, California. This instrument gave reproducible measurements of inclinations accurate to 0° 05′, and of bearing accurate to 2° or 3°. Readings were made at 15-meter intervals. Curve A Fig. 1(p. 183) shows the initial orientation of the pipe, projected on to a vertical plane bearing S. 25° E., the direction of flow as inferred from structures in the glacier. A resurvey weeks later showed no perceptible deformation. Orientation of the pipe one year later, in August 1952, is shown by Curve B Fig. 1. Deformation during this interval is more easily seen if plotted against a straight vertical line (Fig. 2). During the first year no perceptible differential flow occurred in the uppermost 90 meters of the glacier. Below that depth flowage was slight but at a relatively uniform rate except for some irregularity and a small acceleration below 275 meters. Total differential flow between the top and bottom of the 305-meter pipe was only 1.75 meters. The absolute amount of flow is not known, for the test site is too far from fixed triangulation points to permit such a measurement.

Fig. 1

Fig. 2

The deformation is, as yet, too slight to permit firm conclusions as to the mode of flow in this sheet of ice, and further observations of the pipe will have to be made in subsequent years. The results to date do not support the concept of extrusion flow. Deformation of the pipe suggests that flowage occurs more readily at depth than close to the surface, as might be expected, but the surface ice appears to be carried along by the flowing ice beneath in a manner contrary to the mechanism of extrusion flow.

The possibility of extrusion flow below the depth of the bore hole cannot be wholly eliminated, because of the small magnitude of differential flowage recorded so far, but it seems unlikely because extrusion flowage would entail a reversal in direction of the present source.

This work is a part of the Arctic Institute of North America’s Project Snow Cornice and was supported by Office of Naval Research contract N6onr-244–16.