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The Bering and Steller Glaciers of southern Alaska provide the opportunity to investigate relationships between climate and tectonics in a glaciated mountain belt. The glaciers profoundly impact the climate, ecology, and landscape of the northeastern Gulf of Alaska margin. The glaciers flow among and over deformed and eroded rocks of the Yakutat microplate, where geological structures impart topographic variations in the landscape that strongly affect glacier dynamics. The Bering Glacier flows along a tectonic boundary within the microplate that separates two regions of different structural style and history. East of the glacier, erosion of folded and thrust-faulted sedimentary strata creates E-W ridges and valleys oriented at high angle to ice flow. Farther west, second-phase folds and faults are superimposed on these structures, creating mountain blocks with complex structural geometry. Where the second-phase limbs have an E-W structural grain the glaciers flow around broad headlands, and meltwater streams discharge southward through narrow canyons. N to NE trending fold limbs are streamlined by glacial scouring parallel to folded bedding, and the elongated mountains are separated by narrow ice- and water-filled troughs, or flat-floored sediment-filled valleys.

Measurements of ice motion and glacier surface topography are used in conjunction with geological mapping to constrain the location of the tectonic boundary beneath the Bering Glacier. The boundary is inferred to lie beneath the west-central terminus and extend up-glacier, passing west of the Grindle Hills and extending into the Khitrov Hills. The large volume of debris trapped in the Medial Moraine Band along the western edge of the Bering Glacier overlies a NNE-trending bedrock high formed by second-phase folding. The Bering and Steller Glaciers coalesce beneath the Medial Moraine Band, which then divides into several flows of faster and slower moving ice and debris. Thermokarst dominates the glacial structure on the lower part of the moraine band, where ice flow is 20 m/a or less. To the west, the Steller Glacier diverges into several lobes where it flows among remnants of second-phase folds.

The tectonic boundary beneath the Bering Glacier is inferred to be a concealed thrust or oblique-slip thrust fault that rises from the Aleutian megathrust or subduction zone, juxtaposing the second-phase folded terrain against and over the E-trending fold belt beneath the glacier. There is no surface expression of the tectonic boundary because of intense erosion and transport of rock debris by the glacier and meltwater rivers. Trunk river channels beneath the Bering Glacier are presumably affected by remnant structures at its base, where NNE-trending ridges and sediment filled troughs are juxtaposed against E-trending topography oriented at high angle to ice flow. This change in basal topography and structure presumably constricts the basal drainage network opposite a sharp bend in the Khitrov Hills, where surging initiated in 1993. Episodic freezing or deformation by ice flow in this part of the drainage network may create elevated fluid pressure that triggers episodic surging.

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