GLACIAL LANDFORM

any product of flowing ice and meltwater. Such landforms are being produced today in glaciated areas, such as Greenland, Antarctica, and many of the world's higher mountain ranges. In addition, large expansions of present-day glaciers have recurred during the course of Earth history. At the maximum of the last ice age, which ended about 20,000 to 15,000 years ago, more than 30 percent of the Earth's land surface was covered by ice. Consequently, if they have not been obliterated by other landscape-modifying processes since that time, glacial landforms may still exist in regions that were once glaciated but are now devoid of glaciers. Periglacial features, which form independently of glaciers, are nonetheless a product of the same cold climate that favours the development of glaciers, and so are treated here as well. Additional reading The classic text on glacial geology is Richard Foster Flint, Glacial and Quaternary Geology (1971), encyclopaedic coverage including an extensive bibliography. Recent hypotheses and observations on glacial erosion and deposition are included in David Drewry, Glacial Geologic Processes (1986), even though the coverage of glacial landforms is not complete. David E. Sugden and Brian S. John, Glaciers and Landscape: A Geomorphological Approach (1976, reprinted 1984), is an excellent detailed introduction to glacial landforms and the processes that shaped them. More theoretical emphasis can be found in Clifford Embleton and Cuchlaine A.M. King, Glacial Geomorphology, 2nd ed. (1975), and Periglacial Geomorphology, 2nd ed. (1975). A.L. Washburn, Geocryology: A Survey of Periglacial Processes and Environments (1979), contains numerous explanatory photographs and diagrams. A collection of articles is found in Cuchlaine A.M. King (ed.), Periglacial Processes (1976). Edward B. Evenson Gunnar Schlieder