At the ends of the glaciers the subglacial and intraglacial drainage issues from tunnels and forms muddy streams. These usually flow out from the foot of a precipice of ice, down which rills are continually trickling. The streams flowing away from the glaciers are usually rapid, owing to the high grade of their built-up channels, and sweep away large quantities of débris which is deposited along their courses. The streams widen and bifurcate as they flow seaward, and spread vast quantities of bowlders, sand, and gravel over the country to the right and left, not infrequently invading the forests and burying the still upright trees. The deposits formed by the streams are of the nature of alluvial fans, over which the waters meander in a thousand channels. Where this action has taken place long enough the alluvial fans end in deltas; but should there be a current in the sea, the débris is carried away and formed into beaches and bars along adjacent shores. Should these glaciers disappear, it is evident that these great bowlder washes would form peculiar topographic features, unsupported at the apexes, and it might be perplexing to determine from whence came the waters that deposited them. I am not aware that similar washes have been recognized along the southern border of the Laurentide glaciers, but they should certainly be expected to occur there.
Another very striking difference in the appearance of the glaciers above and below the snow-line is due to the prevalence of débris on the lower portion. The melting that takes place below the snow-line removes the ice and leaves the rocks. In this manner the stones previously concealed in the névé are concentrated at the surface, and finally form sheets of débris many miles in extent. So far as my observations go, there is nothing to indicate that stones are brought to the surface by any other means than the one here suggested. Upward currents in the ice that would bring stones to the surface have been postulated by certain writers, but nothing sustaining such an hypothesis has been found in Alaska.
The moraines on the lower extremities of the Alpine glaciers may frequently be separated into individual ridges, which in many instances would furnish instructive studies; but in no case has the history of these accumulations been worked out in detail.
With the appearance of moraines at the surface come a great variety of phenomena due to unequal melting. Ridges of ice sheathed with débris, glacial tables, sand cones, etc., everywhere attract the attention; but these features are very similar on all glaciers where the summer's waste exceeds the winter's increase, and have been many times described.
The general distribution of the moraines of the lower portion of the Alpine glaciers of the St. Elias region merits attention. The moraines themselves exhibit features not yet observed in other regions. From Disenchantment bay westward to the Seward glacier the lower portions of the ice-streams are covered and concealed by sheets of débris. About their margins the débris fields support luxuriant vegetation, and not infrequently are so densely clothed with flowers that a tint is given to their rugged surfaces. On the extreme outer margins of the moraines there are sometimes thickets and forests so dense as to be almost impenetrable. The best example of forest-covered moraines resting on living glaciers, however, is found along the borders of the Malaspina ice-field.
PIEDMONT GLACIERS.
This type is represented in the region explored by the Malaspina glacier. This is a plateau of ice having an area of between 500 and 600 square miles, and a surface elevation in the central part of between 1,500 and 1,600 feet. It is fed by the Agassiz, Seward, Marvine, and Hayden glaciers, and is of such volume that it has apparently displaced the sea and holds it back by a wall of débris deposited about its margin. All of its central portion is of clear white ice, and around all its margins, excepting where the Agassiz and Seward glaciers come in, it is bounded by a fringe of débris and by moraines resting on the ice. Along the seaward border the belt of fringing moraines is about five miles broad. The inner margin of the moraine belt is composed of rocks and dirt, without vegetation, and separated more or less completely into belts by strips of clear ice. On going from the clear ice toward the margin of the glacier one finds shrubs and flowers scattered here and there over the surface. Farther seaward the vegetation becomes more dense and the flowers cover the whole surface, giving it the appearance of a luxuriant meadow. Still farther toward the margin dense clumps of alder, with scattered spruce trees, become conspicuous, while on the outer margin spruce trees of larger size form a veritable forest. That this vegetation actually grows on the moraines above a living glacier is proved beyond all question by holes and crevasses which reveal the ice beneath. The curious lakes scattered abundantly over the moraine-covered areas, and occupying hour-glass-shaped depressions in the ice, have already been described.
From the southern end of the Samovar hills, where the Seward and Agassiz glaciers unite, there is a compound moraine stretching southward, which divides at its distal extremity and forms great curves and swirl-like figures indicating currents in the glacier.
All the central part of the plateau is, as already stated, of clear white ice, free from moraines; at a distance it has the appearance of a broad snow surface. This is due to the fact that the ice is melted and honey-combed during the warm summer and the surface becomes vesicular and loses its banded structure. A rough, coral-like crust, due to the freezing of the portions melted during the day, frequently covers large areas and resembles a thick hoar-frost. Crevasses are numerous, but seldom more than a few feet deep. They appear to be the lower portions of deep crevasses in the tributary streams which have partially closed, or else not completely removed by the melting and evaporation of the surface.
Many of the crevasses are filled with water, but there are no surface streams and no lakes. Melting is rapid during the warm summer days, but the water finds its way down into the glacier and joins the general subglacial drainage. It is evident that the streams beneath the surface must be of large size, as they furnish the only means of escape for the waters flowing beneath the Agassiz, Seward and Marvine glaciers, as well as for the waters formed by the melting of the great Malaspina glacier.