West Fork Glacier is a large glacier in the central Alaska Range, in the Susitna River drainge system. It is adjacent to, and about the same size as, the surge-type Susitna Glacier. Judging from Washburn photography, the last surge of West Fork Glacier was in the 1930s. Balance and velocity measurements in the early 1980s indicated that West Fork Glacier has not achieved balance flux, and, judging from its similarity to Susitna Glacier, T. Clarke predicted that its next surge was imminent. Aerial observations by A. Post and R. Krimmel in late August 1987 indicated slight, but anomalous, crevassing which they suggested could be premonitory to a surge.
We noticed, in early January 1988, that the margins of West Fork Glacier were badly sheared. Observations at the end of January indicated more extensive shearing and crevassing, with much of the glacier affected from low in the ablation area to well above the equilibrium line, including some major tributaries. More observations in early February indicated propagation of the areas of draw-down far up into the accumulation area, and a reasonably well-defined front of active ice propagating into the stagnant ice of previous surges. Small lakes were seen at the edge of the propagating front. During the placement of a marker on the lower glacier, the glacier could be felt lurching ahead at about 1 min intervals.
Water sampling beneath seasonal ice cover of the main streams at the glacier terminus and at about 10 km below (where all the streams converge into a single channel) indicated “low” flow (there are no base-line data) and no trace of turbidity in the water. No trace of flooding was found in the snow bordering the streams, or in the ice cover.
