The Editors,

The Journal of Glaciology

Sirs, Glacier Crevasses

The point has been raised that my remarks in the discussion on the Extrusion Flow paper (Journ. Glaciology, Vol. 1, No. 1, 1947, p. 19), particularly my Figure 4, suggest that transverse crevasses may be formed without the need for a Step in the glacier bed. I gather that the general view is that the presence of transverse crevasses indicates a Step in the rock floor. This is a point of fundamental importance and it must be settled.

My own opinion is that transverse crevasses are not necessarily associated with steps in the bed, but that a Step of any magnitude arising from differences between adjacent strata would produce significant crevasse Systems. I regard the crevasse as indicating a zone of tension in the ice arising from the motion of the glacier contained within its more rigid rock boundaries, and I do not believe it is necessary to have steps in the bed to produce zones of tension.

If only we could find it possible to explore a glacier thoroughly throughout its length and depth, as we do as engineers when investigating landslips, by trenches and borings extending to the limits of movement, I believe many points of the above nature could be settled. Until some large investigation of this nature is undertaken our knowledge will always be severely restricted.