Historic and Prehistoric Fluctuations of Alpine Glaciers in the Mount Garibaldi Map-Area, Southwestern British Columbia

Abstract

Historical, botanical, and geological studies in a part of the Coast Mountains of British Columbia show that all the existing glaciers of that area are retreating from climaxes attained in the early part of the eighteenth century and in the middle of the nineteenth century. A rapid rate of shrinkage, amounting to a loss in depth of as much as 12 1/2 feet of ice annually, has prevailed, however, only since the second and third decades of this century and has coincided approximately with a relatively warm period indicated by meteorological records. In three of four glaciers studied, the maximum advance of the last three centuries exceeded any other since the latter part of the Pleistocene epoch, and one of these three glaciers has been as extensive as it was in 1947 for only about four centuries since the deglaciation of its basin by the Cordilleran ice sheet in late Wisconsin time. For a fourth glacier, however, the advances of the past few centuries failed by far to reach the limits of a much earlier, probably late Pleistocene, advance. Reduction in its potential accumulation area as a result of unusually rapid lowering of its cirque head wall by erosion may account for the anomalous behavior of this glacier. Many low-level cirques, formed by early or pre-Wisconsin alpine glaciation, have not been reoccupied by local bodies of ice during or since the disappearance of the Cordilleran ice sheet.