of Greenland, extensive "icecaps" have formed.
The outer edges of these masses of ice are forced
through the hords in the form of glaciers, which
discliarge icebergs. See Glacier, and the general article Geology.
Geology. The geology of the Arctic lands presents a great variety of features, which, how- ever, are comparable in general to those exhibited in more southern latitudes. Extensive coal beds and numerous fossil remains in sedimentary strata bear evidence that the conditions prevail- ing in former ages were favorable for the de- velopment of a diversified fauna and flora, such as do not at present exist. The Carboniferous strata arc the most significant as to the past cli- matic conditions obtaining in this region. They have been found in Banks Land, North Devon, and Spitzbergen. Coal beds and strata of the Tertiary Age have been discovered in Grinnell Land, and similar deposits are known to occur as far north as 82°, in which poplar, pine, birch, and hazel Hora are represented. In Spitzbergen a Carboniferous flora has been obtained, comprising no less than twenty-six species, some of which are new, but of which others are forms common to the coal measures of England and the Lnited States, Greenland (q.v. ) consists principally of gneisses, schists, and granite, with later in- trusions of basalt, and is noteworthy as the source of the mineral, cryolite. Most of the islands off the North American Continent are made up of crystalline rocks and Paleozoic sedi- ments, of probably Cambrian and Silurian Age. The northern part of Seward Peninsula luis been found recently to be composed of metamorplu>se<l sediments of undetermined age, and of Cretace- ous limestones. The great island groups north of Euro-Asia, including Franz-Josef Land, are formed of early Paleozoic and pre-Cambrian rocks overlaid by basalt. Very little is known as to the geological features of northern Siberia.
The Arctic Ocean is the body of water en- circling tlie North Pole, and included between the northern boundaries of Europe, Asia. North America, Greenland, and the north Atlantic Ocean above the Arctic Circle, with which latter ocean it is in open connection, while it is in communication with the Pacific Ocean only tlirough the narrow Bering Strait. It drains a vast area, including the northern parts of North America and of Asia. The great rivers. Obi, Yenisei, and Lena, in Asia, and the Mac- kenzie, in Canada, empty into this ocean. Its area is estimated at between 4.000,000 and 5,000,000 square miles. How nuich of this area is covered by land is uncertain ; but the con- siderable depth of soundings taken by Arctic explorers would seem to indicate an extensive polar -sea. It is hardly probable that any im- portant land areas exi.st in the region that stretches from the pole southward, to the north- ern point of the archipelago above Greenland, to the mouth of the JIackenzie, to Bering Strait, to the northern point of Siberia, and to the northern point of Franz-.Josef Land. The water region immediately surrounding the pole is covered with great fields of ice, which are frozen together in winter, but become separated to a greater or less degree (especially at the edges where ice floes are formed ) during the summer. This ice area is called the ice-pack, and it extends somewhat to the southward of latitude 75° N. above Bering Strait and the adjoining American and Asiatic coast, between the limits of longitude 160° E. and 130° W. : to the west- ward and eastward of this region the pack- limit retreats northward: and in longitude 120° W., it is found at about latitude 78° N. ; in longi- tude 90° W., at about latitude 78° N. ; in longi- tude 85° W., at about latitude 81° N. ; in longi- tude 50° W., at about latitude 83° N. On the east coast of Greenland the ice-pack descends to latitude 78° N., to retreat again to 82° or 83° N., north of Spitzbergen and Franz-.Josef Land, where this latitude is preserved as far east as longitude 100° east of Greenwich, when the detour toward the south begins, which reaches its limit at about longitude 173° E. This ice is kept in sluggish motion, principally by the winds, in such a manner that a vessel lodged in the ice at a point north of Alaska, or even of Siberia, would gradually drift toward the pole and, passing bej'ond that, would con- tinue soutliward until set free from the ice near Spitzbergen or Greenlaiul. Nansen made such J a drift in 1893-96. The depth of the Arctic Ocean is variable, being very shoal (only a few hundred feet deep) north of western North America and eastern Asia, where, however, measurements have not been made above latitude 75° north, and very deep (7000 to 15,000 feet) near where its waters join the North Atlantic. Northward of the continent of Europe the depth is from 600 to 1200 feet, and northward of Spitz- bergen and Franz-.Josef Land 10.000 feet. The Arctic Ocean is apparently afl'ccted by tides, in uhicli the monthly variations are more important than are the semi-diurnal, but both the.se are masked by the influence of the winds and the ice. The assumption that a great portion of the Arctic Ocean has for a long time been covered with solid pack of ice has suggested for it the name of Paleocrystie Sea, or the Sea of Ancient Ice.
Arctic Currents. The open connection between the North Atlantic and the Arctic Oceans offers an opportimity for a free interchange of waters between the two. On the east side of the North Atlantic the drift of the surface water is northward, and on the west side the current flows southward. This latter, called the Arctic Current. passes from the Arctic Ocean through the Irmingen Sea of Nordenskjiild, between Iceland and Greenland ; thence along the eastern coast of Greenland ; rounds Cape Farewell, and flows up Davis Strait to about latitude 64° N. Here it probably turns toward the west and joins the Labrador Current. There is another movement of water southward from the Arctic Ocean through the straits and bays which communicate with Bartin's Bay. The Labrador Current flows southward along the west coast of Baffin's Bay, past Labrador and Newfoundland, until it dips into the eastward drift of the warmer waters off the Banks of Newfoundland, where the divers currents prevailing are but feeble. It has been supposed that a part of this current continued southward along the Nova Scotian and New England coast, but some other explanation must be offered for the cold current which exists on that coast. The Labrador Current, which has a very low water temperature, carries with it ice-bergs and floes, which eventually disappear by melting in the vicinity of Cape Kace. In this latter region heavy fogs ])revail whenever winds from the south carrv moist, warm air over the
