The most striking features of large glaciers are the medial moraines, the lakes and streams on its surface, the wild ice cataracts correspond ing to the cascades and rapids of rivers, and the discharging frontal wall, with its icebergs. Glaciers vary widely in size and form; they may be classified as follows: (a) Continental glaciers, of which only two now exist, the Greenland and South Polar ice caps, dome-shaped ice deposits covering the entire face of nature beneath. Similar in char acter to the continental glaciers are the ice caps of Norway, Iceland and Franz Josef Land and the masses of °inland ice') (and snow) in Spitzbergen, Nova Zembla, Baffin Land, Grin nell Land and Ellesmere Land.
(b) Glaciers of the first order, which are more or less river-like, flow into the sea, and terminate in berg-discharging ice cliffs.
(c) Glaciers of the second order, which approach the sea, but do not enter it, and of course do not discharge icebergs, waste from melting and evaporation equaling the snow supply.
(d) Glaciers of the third order, residual branches of those of the second, separated and made independent by the melting away of the trunks to which they belonged. Nearly all the glaciers of the world are now of this order. The last three types are often called valley or alpine glaciers.
Distribution of Most of the glaciers of North America are distributed along the mountain ranges of the Pacific coast from central California northward. About 65 small residual glaciers a mile or less long still linger on the Sierra Nevada of California between lat. 30' and at an elevation of 11,000 to 12,000 feet above sea-level. Groups of larger glaciers drain the snow-fields of Mount Shasta and the high volcanic mountains of the Cascade Range in Oregon and Washington. From ice crowned Mount Rainier, 14,600 feet high, eight glaciers, 5 to 10 miles long, descend into the forests to within 3,000 and 4,000 feet of sea level. The btoad, lofty mountain chain ex tending along the coasts of British Columbia and southeastern Alaska is generally ice-laden; the upper branches of the main valleys are oc cupied by glaciers, which gradually' increase in size and descend lower, up to the highest and snowiest region of Alaska between lat. 56° and 61°, where a considerable number flow into arms of the sea. This is the region of great est glacial abundance on the continent To the north of lat. the glaciers gradually
diminish in size to about lat. 62° 30' or 63'. Beyond this, to the north end of the continent, few, if any, glaciers now exist, the ground be ing comparatively low and the snowfall light Glaciers of the third order, a mile or two to 15 or 20 miles long, fill the upper canyons and hollows of the highest region in countless thousands.
The large glaciers of the second order num ber about 100. They are distributed along the coast from the mouth of the Stickeen River to Cook Inlet and the Alaska Peninsula. The ex panded fan-shaped ends of many of this order are from two to four or five miles wide and Constitute what are known as bulb glaciers or, if very large, piedmont glaciers. The largest among these are the Malaspina Glacier, the -Miles, Yakutat, Grand Plateau, Crillion and La Perouse, fronting the sea along the Saint Fliac and Fairweather mountains. The Malaspina is the largest of them all, being about 20 miles long and 65 or 70 miles wide,— a grand undu lating ice prairie sloping gently from the base of the Saint Elias Mountains, and separated from the sea by a girdle of forested moraines five or six miles wide, except at Icy Cape, where it presents bluffs of pure ice that are being continually undermined by the waves and are discharging icebergs into the sea. The La Perouse also presents ice bluffs to the open ocean, which at high tide are wave-washed, and small bergs are occasionally detached ; but far the greater number terminate a mile or two from the tide line, back of moraines in rather low-spreading crevasse-gashed brows, over which one may-easily climb.
The great glaciers of the first order flowing out into deep ocean water and discharging fleets of icebergs number about 31. the south most, flows into the Le Conte Fiord in lat. 56° 50', four into branches of Holkam Bay, one into Taku Fiord, nine into the Glacier Bay fiords, two into Lituya Bay at the base of Mount Fairweather, three into Disenchantment Bay and 11 into the wild fiords of Prince Wil liam Sound, the northmost being a little above the 61st parallel. The birth of icebergs from this type of glacier is attributed to the thin ning of the foot of the glacier from above, and the upward force exerted by the lighter specific gravity of ice as compared with sea water at a depth of several hundred feet.