Air pockets and secondary habits in ice from lateral-type growth

Abstract. Often overlooked in studies of ice growth is how the crystal faces grow laterally. This paper explores the implications of such lateral-type growth and how it may explain air pockets and other secondary features of vapor-grown ice in air. For example, using a new crystal-growth chamber, we observed air pockets forming at crystal corners when a sublimated crystal is regrown. This and other observations support the idea that the lateral spreading of a face, and its (in some cases) extension as a thin overhang over the adjoining region, is driven by a flux of surface-mobile admolecules across the face to the lateral-growth front. Inspired by recent work on this topic by Prof. A. Yamashita of Osaka Kyoiku University, we call this flux adjoining surface transport (AST) and the extension overgrowth protruding growth, then apply the concepts to observed ice and snow crystals, including some from a cloud chamber and others from our experiments. We also suggest that such lateral-type growth may explain other air pockets, droxtal centers in dendrites, hollow terracing and banding, multiple-capped columns, scrolls, trigonals, and sheath clusters. For dendrites and sheaths, AST may increase their maximum dimensions and round their tips.