AMP: The Ahklun Mountains Region

The Ahklun Mountains form the highest range in Alaska west of the Alaska Range and north of the Alaska Peninsula. They trend about 250 km northeast to southwest and are flanked by the Kuskokwim River and Bristol Bay lowlands on the west and east, respectively. The range reaches its highest elevations in the northeast, where summits exceed 1500 m asl and shelter dozens of modern-day glaciers. Repeated glaciations during the Pleistocene have excavated an extensive network of valley troughs, most of which are controlled by underlying bedrock structure. Along the steep eastern range front, the troughs are filled by an interconnected system of elongate, over-deepend lakes (>400 m deep) dammed by terminal moraines. The southern (coastal) and western (Kuskokwim) flanks are dissected by broad, fault-bounded valleys, forming a more diffuse mountain front of rolling uplands punctuated by small, rugged massifs. Beyond the mountains, at the limits of glacier advances, moraines and ice-thrust ridges form the principal topographic features in the lowlands. Erosion by storm waves and coastal rivers has exposed many kilometeres of unconsolidated Quaternary sediment, particularly along coastal embayments, and bedrock along rocky headlands.