The National Geographic Magazine, Vol. III. (Complete), 1891

by Various

FIGURE 1—Diagram illustrating the Formation of Icebergs

As the sea-cliff of ice recedes and the submerged terrace increases in breadth there comes a time when the buoyancy of the ice at the bottom exceeds its strength, and pieces break off and rise to the surface. The water about the ends of the glaciers is so intensely muddy that the submerged ice-foot is hidden from view, and its presence would not be suspected were it not for the fragments occasionally rising from it. The sudden appearance of these masses of bottom ice at the surface is always startling. While watching the ice-cliffs and admiring the play of colors in the deep crevasses which penetrate them in every direction, or tracing in fancy the strange history of the silent river and wondering in what age the snows fell on the mountains, which are now returning to their parent, the sea, one is frequently awakened by a commotion in the waters below, perhaps several hundred feet in front of the ice-cliffs. At first it seems as if some huge sea-monster had risen from the deep and was lashing the waters into foam; but soon the waters part, and a blue island rises to the surface, carrying hundreds of tons of water, which flows down its sides in cataracts of foam. Some of the bergs turn completely over on emerging, and thus add to the tumult and confusion that attends their birth. The waves roll away in widening circles, to break in surf on the adjacent shores, and an island of ice of the most lovely blue floats serenely away to join the thousands of similar islands that have preceded it. The fragments of the glacier rising from the bottom in this manner are usually larger than those broken from the faces of the ice-cliffs, sometimes measuring 200 or 300 feet in diameter. Their size and the suddenness with which they rise would insure certain destruction of a vessel venturing too near the treacherous ice-walls.

At the time of our visit to Haenke island, the entire surface of Disenchantment bay and all of Yakutat bay as far southward as we could see formed one vast field of floating ice. Most of the bergs were small, but here and there rose masses which measured 150 by 200 feet on their sides and stood 40 or 50 feet out of the water. The bergs are divided, in reference to color, into three classes—the white, the blue, and the black. The white ones are those that have fallen from the face of the ice-walls or those that have been sufficiently exposed to the atmosphere to become melted at the surface and filled with air cavities. The blue bergs are of many shades and tints, finding their nearest match in color in Antwerp blue. These are the ones that have recently risen from the submerged ice-foot, or have turned over owing to a change of position in the center of gravity. Rapid as is the melting of the ice when exposed to the air, it seems to liquefy even more quickly when submerged. The changes thus produced finally cause the bergs to reverse their positions in the water. This is done without the slightest warning, and is one of the greatest dangers to be guarded against while canoeing among them. The white color presented by the majority of the bergs is changed to blue when they become stranded, and the surf breaks over them and dissolves away their porous surfaces. A few of the bergs are black in color, owing to the dirt and stones that they carry on their surfaces or frozen in their mass. Quantities of débris are thus floated away from the tide-water glaciers and strewn over the bottoms of the adjacent inlets.

This digression may be wearisome, but one cannot stand on Haenke island without wishing to know all the secrets of the great ice-streams that flow silently before him.

Returning from our commanding station at the summit of the island to where we left our canoe, we were surprised and not a little startled to find that the tide had run out and left the strand between our canoe and the water completely blocked with huge fragments of ice. There was no way left for us to launch our canoe except by cutting away and leveling off the ice with our axe, so as to form a trail over which we could drag it to the water. This we did, and then, poising the canoe on a low flat berg, half of which extended beneath the water, I took my place in it with paddle in hand, while Christie and Crumback, waiting for the moment when a large wave rolled in, launched the canoe far out in the surf. By the vigorous use of my paddle I succeeded in reaching smooth water and brought the canoe close under the cliff forming the southern side of the cove, where the men were able to drop in as a wave rolled under us.

We slowly worked our way down the bay through blue lanes in the ice-pack, against an incoming tide, and reached our tents near sunset. Thus ended one of the most enjoyable and most instructive days at Yakutat bay.

FROM YAKUTAT BAY TO BLOSSOM ISLAND.

Our camp on the shore of Yakutat bay was held for several days after returning from Haenke island, but in the meantime an advance-camp was established on the side of the Lucia glacier, from which Mr. Kerr and myself made explorations ahead.

Before leaving the base-camp I visited Black glacier for the purpose of taking photographs and studying the appearance of an old glacier far spent and fast passing away. This, like the Galiano glacier, is a good example of a great number of ice-streams in the same region which are covered from side to side with débris. The cañon walls on either side rise precipitously, and their lower slopes, for the height of 200 or 300 feet, are bare of vegetation. The surface of the glacier has evidently sunken to this extent within a period too short to allow of the accumulation of soil and the rooting of plants on the slopes. The banks referred to are in part below the upper limit of timber growth, and the adjacent surfaces are covered with bushes, grasses, and flowers. Under the climatic conditions there prevailing, it is evident that the formation of soil and the spreading of plants over areas abandoned by ice is a matter of comparatively few years. It is for this reason that a very recent retreat of Black glacier is inferred. Many of the glaciers in southern Alaska give similar evidence of recent contraction, and it is evident that a climatic change is in progress which is either decreasing the winter's snow or increasing the summer's heat. The most sensitive indicators of these changes, responding even more quickly than does the vegetation, are the glaciers.