Ground penetrating radar (GPR) profile parallel to the axis of Middle Fan at McCarthy Glacier extending from the glacier onto the icy debris fan (IDF). (A) Ground photo showing the location of GPR profile (red line). (B) Unmigrated GPR profile on the IDF showing details of area denoted by black rectangle in (C). Note that elevations are not displayed. Depth based on wide-angle reflection and refraction (WARR) sounding on IDF providing a normal moveout (NMO) velocity of 0.158 m/ns and two-way travel time (TWTT) of 435 ns. Solid line denotes prominent reflection separating layered reflections interpreted as IDF deposits above and more abundant hyperbolic reflections below interpreted as either crevasses or boulders (lithic clasts). The dotted lines denote reflections that become less defined with depth. (C) Migrated and elevation-corrected GPR profile extending from glacier (left) up onto mid-fan area (right) using same NMO velocity. Elevations from RTK-GPS were used to display ground surface elevations, above sea level (ASL). The black dotted line connects prominent reflectors at depth interpreted to be the bedrock interface. We interpret a fan thickness of 45 m at mid-fan and a glacier thickness of 82 m.
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