Gla·cial a.
 1. Pertaining to ice or to its action; consisting of ice; frozen; icy; esp., pertaining to glaciers; as, glacial phenomena.
 2. Chem. Resembling ice; having the appearance and consistency of ice; -- said of certain solid compounds; as, glacial phosphoric or acetic acids.
 Glacial acid Chem., an acid of such strength or purity as to crystallize at an ordinary temperature, in an icelike form; as acetic or carbolic acid.
 Glacial drift Geol., earth and rocks which have been transported by moving ice, land ice, or icebergs; bowlder drift.
 Glacial epoch or Glacial period Geol., a period during which the climate of the modern temperate regions was polar, and ice covered large portions of the northern hemisphere to the mountain tops.
 Glacial theory or Glacial hypothesis. Geol. See Glacier theory, under Glacier.

 ◄ ►


 Gla·cier n.  An immense field or stream of ice, formed in the region of perpetual snow, and moving slowly down a mountain slope or valley, as in the Alps, or over an extended area, as in Greenland.
 Note: ☞ The mass of compacted snow forming the upper part of a glacier is called the firn, or névé; the glacier proper consist of solid ice, deeply crevassed where broken up by irregularities in the slope or direction of its path. A glacier usually carries with it accumulations of stones and dirt called moraines, which are designated, according to their position, as lateral, medial, or terminal (see Moraine). The common rate of flow of the Alpine glaciers is from ten to twenty inches per day in summer, and about half that in winter.
 Glacier theory Geol., the theory that large parts of the frigid and temperate zones were covered with ice during the glacial, or ice, period, and that, by the agency of this ice, the loose materials on the earth's surface, called drift or diluvium, were transported and accumulated.

 ◄ ►