Superior, LAKE, the largest body of fresh water on the globe, is the highest and most western of the great lakes lying between Canada and the United States. It is bounded on the N. and E. by Ontario, on the S. by Michigan and Wisconsin, and on the NW. by Minnesota. Greatest length, 412 miles; greatest breadth, 167 miles; area, 32,200 sq. m.—nearly that of Ireland. The surface of the lake is 601 feet above the level of the sea, and its mean depth about 475 feet; its maximum depth is 1008 feet, or 406 feet below the level of the sea. Its surface has an elevation of 20 feet above that of Lakes Huron and Michigan; this difference occurs in the rapids of St Mary's River, the only outlet (see SAULT STE MARIE), where the average discharge is 86,000 cubic feet per second. Lake Superior, being situated very near the watershed between Hudson Bay and the Mississippi, receives no rivers of importance, although hundreds of small rivers pour themselves into it, the largest the St Louis and the Nipigon. Its aggregate drainage area (including its own area) is 82,800 sq. m. (Compare the articles on the four other lakes of the system, and those on Victoria Nyanza, Baikal, &c.) Near Dog Lake (318 miles by rail E. of Port Arthur) a short portage connects streams flowing to Lake Superior with others flowing north to Hudson Bay. The Sault Ste Marie Canal ( mile, opened 1895) gives continuous navigation from the head of Lake Superior to the sea, 2384 miles.
The bold northern coast is fringed with rocky islands, some rising from deep water to 1300 ft. above the lake. The largest island is Isle Royale, which is 44 miles long. The southern shore is generally lower and more sandy, with occasional ridges of limestone. Keweenaw Point (q.v.) projects far into the lake. At Grand Isle Bay, about 100 miles W. of Sault Ste Marie, are the Pictured Rocks, cliffs of sandstone from 50 to 200 feet high, in many places presenting fantastic forms, and marked by numerous vertical bands and blotches of red and yellow. The boundary line between Canada and the United States is drawn through the centre of the lake from its outlet to the mouth of Pigeon River, but is diverted so as to include in the United States Isle Royale.
The water of Lake Superior is singularly pure and transparent. It never freezes over, but the shore ice prevents navigation in winter. The lake also is subject to very violent storms; waves have been observed, during protracted autumn gales, 15 to 18 feet high. It has the small tides common to the great lakes (see MICHIGAN), and also the sciches seen in Swiss lakes—a regular series of small waves, or pulsations, at intervals of about ten minutes.
The rocks around the lake are very ancient, belonging principally to the Laurentian and Huronian systems of the Azoic series, overlaid in some places, especially on the south side, with patches of the Lower Silurian (soft sandstones). There is everywhere much evidence of glacial action. On the north side, both on the islands and shores, copper and silver are worked, especially at Thunder Bay; while the copper and red hematite iron ores of the south side are celebrated for their extent and richness (see COPPER, p. 464). The principal towns on the Canadian side are Sault Ste Marie and Port Arthur, and on the American side Duluth, Superior, and Marquette, all of which are discussed separately. The Canadian Pacific Railway passes along the northern shore. See Crosman's Chart of the Great Lakes (Milwaukee, 1888).