On Some Physical Properties of Ice

Abstract

INTRODUCTORY NOTE BY T. C. CHAMBERLIN While many of the more obvious problems of ice and ice action have been solved in a general way, there remain not a few questions of a more refined sort which require solution before glaciology can rest on a secure foundation. Some of these questions are critically important for they bear radically. on interpretations that have already been widely accepted and are currently taught. More extended and more critical field studies are required to solve some of these questions while the solution of others depends on more discriminative and exact laboratory experimentation. All of them call for more searching analyses of the problems themselves, as a source of guidance in field work and in experimentation, as also in the interpretation of results. The glacialists working at Chicago have been trying to do their bit toward the solution of some of these problems and have had under way for some time a series of attacks along several lines in both field and laboratory. This paper presents the preliminary results of a careful series of laboratory determinations carried out by Professor Motonori Matsuyama, of the Department of Geophysics of the Kyoto Imperial University, Japan, who has been spending the year at Chicago. When McConnell, followed by Miigge, announced that ice crystals are minutely laminated in planes normal to their optical axes and that movement along these planes was notably easier than in other directions, it was felt by many that these disclosures offered a happy solution of the anomaly of glacial movement which seemed to be a quasi-fluidal flow in a body obviously rigid. But later critical studies raised serious doubts as to the actual participation of the gliding planes in ordinary glacial motion, and so the subject came to demand more refined examination. Up to date, no one, so far as I know, has determined what is the measure of the resistance to motion along these planes compared with the stresses actually brought to bear upon them in ordinary glacial motion. Nor has it been shown whether the relation of these gliding planes to one another is of the elastic or the viscous order. But even if these properties were known, there would still remain the radical question whether glacial motion actually takes place by means of movements along these planes-or in any other way within the constituent crystals-or whether it is essentially a motion between the constituent crystals. There are here 607

Results of Preliminary Experiments on the Plasticity of Ice Crystals

“…Besides the known slip plane (0001) others have been conjectured 4 , 5 . Rigsby 5 has deduced glide planes from the textures found on Emmons Glacier and the planes (112) and (102) or (114) are given, but the known bisal glide has disappeared.…”

“…The glide plane for ice, which belongs to one of the crystal classes D 6 h , D 3 h or C 6 v is (0001) (McConnel 1 ; Mügge 2 ; Mügge 3 ; Matsuyama 4 ). A glide direction has not been reported, but Mügge observes: “… dass man einzelne solcher Blätter oder vielmehr Lagen solcher ganz aus dem Eiskristall herausschieben kann, und dass die Richtung, in welcher man schiebt, anscheinend fast gleichgültig ist, wenn sie nur in Basis (also der Ebene der Blättchen) liegt…” The conditions for glide, which relate observed glide elements with the structure of the crystal, give in fact the basal plane (0001) with two bonds per unit cell as the plane with the minimum molecular binding energy and so as the probable glide plane.…”

Shear-Stress Fabrics of Ice and Quartz: Some Comments on a Paper by Dr. H. Bader

“…Early in the paper (p. 519) it is stated that the crystallographic basal plane is the only reported plane of lattice slippage in ice. In this connection 6 it may be mentioned (1) that Matsuyama 7 and Rigsby 10 have independently put forward evidence indicating or suggesting the presence, in ice, of glide-planes other than the basal plane; (2) that, according to Hawkes, 3 slip within ice crystals takes place in part along the basal plane and in part along internal fracture surfaces; (3) that Turner and Ch’ih, 14 in a recent petrofabric account of the artificial deformation of dry marble, state that some type of intra-crystalline movement in calcite, other than that connected with the development of optically detectable twin-plane gliding, has played a part in deformation, and has left no visible internal evidence of its activity .…”