Quaternary geology, Cold Bay and False Pass quadrangles, Alaska Peninsula

Recent mapping and interpretation of Quaternary geologic features has improved our understanding of the interaction between volcanic, glacial, and tectonic activity in the Cold Bay and False Pass 1:250,000-scale quadrangles on the Alaska Peninsula. The glacial and volcanic record of the map area strongly suggests that continental-shelf glaciations and two massive volcanic centers were the dominant controls over landscape development during Pleistocene time. Ancestral Morzhovoi and Emmons Volcanoes were major impediments to flow of shelf glaciers during much of the Pleistocene. Our mapping suggests that the area around Emmons Volcano may have also been an important source area for glaciers during this period. Our data further indicate that Frosty Volcano developed late in the Pleistocene, having had no apparent impact on early Brooks Lake glacial advances but serving as a source area for later glacial advances during late Brooks Lake time. We also believe that major Holocene eruptions of Frosty Volcano have yielded multiple debris and ash flows resulting in the construction of a new south summit cone that filled an earlier crater. Frosty Volcano was the source area for multiple Holocene glacial advances, and its flanks preserve the best record of Neoglacial activity in the map area.