Glaciers cover only about 5 percent of Alaska today, but they spread over as much as half of the state during the most widespread advances of the late Cenozoic (Fig. 1). Both modern and ancient glaciers have been most extensive in southern Alaska, where they were close to moisture sources in the North Pacific Ocean and the Gulf of Alaska (Fig. 2). Glaciers were smaller farther to the north because the nearest water bodies were icecovered for much of the year and broad continental platforms were emergent during times of glacioeustatic sea-level lowering. The repeated glaciations of late Cenozoic time had great impact even on nonglaciated parts of Alaska, where they caused formation of proglacial lakes, construction of outwash terraces, loess deposition, and isostatic depression of coastal lowlands. Because the Alaskan glacial record interrelates with so many other physical processes and climate-related features, it provides the fundamental stratigraphic framework for the late Cenozoic history of much of the state.
The positions of readily accessible glaciers along the southeastern Alaskan coast were recorded during 18 th century explorations of La Perouse, Cook, Vancouver, and others, and detailed studies of those glaciers and their fluctuations began near the close of the 19th century (Reid, 1896; Gilbert, 1904; Tarr and Martin, 1914). Compilations of the statewide glacial record have been published by Capps (1932), Pewe and others (1953), Karlstrom and others (1964), Coulter and others (1965), and Péwé (1975).
Ancient as well as modern glaciers in Alaska were primarily alpine in character. Glaciers
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The Geology of Alaska
You get a comprehensive overview of the geology, tectonic evolution, and mineral resources of Alaska and adjacent areas of the continental margin. Plates include state-wide maps showing geology, physiography, lithotectonic terranes, metamorphic rocks, igneous rocks, sedimentary basins, isotopic age data, neotectonics, isostatic gravity, magnetics, and metallic mineral deposits. Summaries of bedrock geology and geologic history are given for eleven large regions of Alaska and adjacent offshore areas. Twenty topical chapters synthesize data on metamorphic and igneous rocks; major onshore and offshore sedimentary basins; the paleomagnetics evidence for latitudinal displacements and rotations, glacial history and periglacial phenomena; and the occurrence, evolution, and potential of Alaska's vast resources of petroleum, coal, and metallic minerals. A summary chapter provides an overview and presents a possible model for Alaska's Phanerozoic evolution. The Geology of Alaska is the largest publication produced in the Decade of North American Geology program, a fitting tribute to this magnificent area.