LANDFORM DEVELOPMENT AND SYSTEMATIC RETREAT OF BERING GLACIER, ALASKA

The 1993-1995 surge of Bering Glacier forced ice onto the stoss side of Weeping Peat Island, overriding previously deposited till, outwash, and lake sediments. The maximum surge extent is identified by push moraines one to ten meters high and kettles at the sandar heads. The maximum surge limit of all landforms and ice-margin positions was measured by GPS, and subsequent measurements during retreat between 1995 and 2001 illustrate the sequence of landform development. Glacier retreat from the maximum position varied from 191m on the southern edge of the Island, at Tsiu Lake, to 685m at Tsivat Lake, on the northern edge. The landforms developed in this environment are the result of direct glacial or glaciofluvial/lacustrine processes and each may be either erosional or depositional. Large volumes of sediment were transported and deposited, illustrated by marked lowering of topography, vast sedimentation in prograding deltas, and a large steep sided depression at an outburst conduit carved by subglacial meltwater. Constructional and destructional processes have altered more than 650,000 m² of the surface of Weeping Peat Island and deposited more than 190,000,000 m² of fine sand and silt in proglacial Tsivat and Tsiu Lakes.