Controversy has long centered about the problem of glacial motion and the physical properties of glacial ice. R. T. Chamberlin has demonstrated by experiment1 that glacial ice, subjected to shearing stress, can be faulted and overthrust in the same manner as rock. On the other hand, the late R. S. Tarr and O. D. Von Engeln have persistently maintained2 that glaciers, although composed of ice which is a crystalline solid, nevertheless, exhibit the characteristics of a plastic or viscous type of flow, and easily adapt themselves without rupture to the irregularities of the terrain over which they pass. H. Hess3 revoiced the discussion recently by championing the theory of plastic flow.
Observation in the Alps and in Alaska has led the writer to concur with Chamberlin that, in all probability, glacial ice behaves in both ways. Not one of the glaciers visited by the writer during his field experience . . .