Fig. 228.—The Rhône glacier. (Reid.)
Fig. 229.—Characteristic end of a North Greenland glacier. North side of Herbert Island, Inglefield Gulf.
Fig. 230.—The end of an alpine (Forno, Switzerland) glacier. (Reid.)
Fig. 231.—Deploying end of a North Greenland glacier.
Where ice-caps are developed on plateaus whose borders are trenched by valleys, ice-tongues from the edge of the ice-cap often extend down into the valleys and give rise to one type of valley glacier (Figs. [224] and [227]). A second and more familiar type of valley glacier occupies mountain valleys, and is the offspring of mountain snow-fields ([Fig. 228]). The former are confined chiefly to high latitudes, and are distinguished as polar or high-latitude glaciers (Figs. [227] and [229]); the latter are known as alpine glaciers (Figs. [228] and [230]). The end and side slopes of polar glaciers are, as a rule, much steeper than those of alpine glaciers. When a valley glacier descends through its valley to the plain beyond, its end deploys, forming a fan ([Fig. 231]). The deploying ends of adjacent glaciers sometimes merge, and the resulting body of ice constitutes a piedmont glacier ([Fig. 232]). At the present time, piedmont glaciers are confined to high latitudes. In some cases the snow-field that gives rise to a glacier is restricted to a relatively small depression in the side of a mountain, or in the escarpment of a plateau. In such cases the snow-field and glacier are hardly distinguishable, and the latter descends but little below the snow-line. In many cases it does not even enter the narrow valley which leads out from the depression occupied by the snow-field. Such a glacier is nestled in the face of a cliff, and may therefore be called a cliff glacier[124] (Figs. [233] and [234]). The snow-field of a cliff glacier is sometimes no more than a great snowdrift, accumulated through successive years. Cliff glaciers are often as wide as long, and are always small, and between them and valley glaciers there are all gradations ([Fig. 235]). Occasionally the end of a valley glacier, or the edge of an ice-sheet reaches a precipitous cliff, and the end or edge of the ice breaks off and accumulates like talus below. The ice fragments may then again become a coherent mass by regelation, and the whole may resume motion. Such a glacier is called a reconstructed glacier. The precipitous cliffs of the Greenland coast furnish illustrations.
