As we are to see, there are other noteworthy differences between continental and mountain glaciers, in the manner of their sculpture of the lithosphere, so that long after they have disappeared the characters of each are easily identified in their handiwork. How the lower clouds are forced upward and so compelled to give up their moisture to feed the mountain glaciers, and how the upper clouds are pulled downward to nourish the glaciers of continents, can be best understood after the characteristics of each glacier class have been studied.
THE CONTINENTAL GLACIERS OF POLAR REGIONS
FIG. 299.—Map of Greenland showing the area of inland-ice and the routes of different explorers.]
=The inland ice of Greenland.=—In Greenland and in Antarctica the land is almost or quite buried under a cover of snow and ice—the so-called “inland ice”—which always assumes the surface of a very flat dome or shield. In Greenland there is found a marginal ribbon of land generally from five to twenty-five miles in width (Fig. 299), but in Antarctica all the land, with the exception of a few mountain peaks, is inwrapped in a mantle of ice which is also extended upon the sea in a broad shelf of snow and ice. Neither of these vast glaciers has been explored except in its marginal portion, yet such is the symmetry of the profiles along the routes traversed, and such the flatness and monotony of the snow surface within the margins, that there is little reason to doubt that the profile made along Nansen’s route in southern Greenland would, save only for magnitude, fairly represent a section across the middle of the continent (Fig. 300).
=The mountain rampart and its portals.=—As soon as we examine the coastal belt we observe that the “Great Ice” of Greenland is held in by a wall of mountains and so prevented from spreading out to its natural surface in the marginal portions. Through portals of the inclosing mountain ranges—the _outlets_—it sends out _tongues_ of ice which in many respects resemble certain types of mountain glaciers.
FIG. 300.—Profile in natural proportions across the southern end of the continental glacier of Greenland, constructed upon an arc of the earth’s surface and based upon Nansen’s profile corrected by Hess. The marginal portions of the profile are represented below upon a magnified scale in order to bring out the characters of the marginal slopes.]