At the head of this body of water there is a little hotel for the accommodation of visitors, and the Stehekin River, which is steadily at work filling up the lake, hurries past its doors. Since the melting of the glacier which once filled the cañon, the river has built a delta fully half a mile out into the water.
The lake has the appearance of filling an old river valley or cañon. Perhaps the latter is the better name because the bed is so narrow and deep. This cañon winds among the mountains just like other cañons in which rivers are flowing, but it has no outlet at the present time. In some way a dam has been formed, and the cañon, filling with water to the top of the dam, has become a lake.
Soundings have shown that the water is fourteen hundred feet deep; that is, a little more than a quarter of a mile. With the exception of Crater Lake, in Oregon, this is the deepest body of water in the United States. It is also interesting to note that the bottom of the lake is fully three hundred feet below the level of the ocean.
How could a river cut a channel for itself so far below the ocean level? Rivers cannot do work of this kind unless they have a swift current; moreover, as they empty into the ocean, their beds must be above sea level. Some people think that the great glacier, which certainly at some time occupied the depression in which the lake lies, dug out the cañon. This glacier was over three thousand feet in thickness, for the rocks are grooved and polished to a height of nearly two thousand feet above the surface of the water. It is, nevertheless, improbable that the glacier did anything more than deepen and widen the cañon somewhat. It was certainly made, as we at first supposed, by a river which flowed through it at some remote period. At that time the land of our Pacific coast must have stood many hundred feet higher than it does now.
FIG. 59.—GOAT MOUNTAIN, NORTH SHORE OF LAKE CHELAN
The surface of Lake Chelan is a little more than three hundred feet above the bed of the Columbia River, which flows through a deep cañon only three miles distant. If we could remove the dam of glacial boulders and gravel at the lower end of the lake, the water would be lowered only three hundred feet. The lake would not be drained, for it is very much deeper. Now here is another puzzle for us: the bottom of the lake is more than one thousand feet below the level of the Columbia. We shall have to go still farther back into the past to get a satisfactory explanation this time.
Hundreds of thousands of years ago there was no plateau filling central Washington, and no Columbia River crossing it. The Cascade Range stood where we see it to-day, and the region of the plateau was a broad valley, toward which flowed the streams that had already cut cañons upon the eastern side of the range. These streams probably united in a river emptying westward into the Pacific by a course now unknown. The shores of the ocean were farther west than at present, for the land stood higher.
The cañon of Lake Chelan was made by a river of this period, which through many long years gradually deepened and enlarged its channel. The river worked just as we see rivers working at the present time, for throughout all the history of the earth rivers have not changed their habits. Then came the long period of volcanic eruptions. Our Northwest was flooded by fiery lava, which built up the Columbia plateau and buried under thousands of feet of rock the old river valley into which the cañon of Chelan emptied.
Then streams of water began to flow over the plateau from the higher mountains above the reach of the lava. These streams formed the Columbia River, which sought the easiest way to the sea, and finally excavated a cañon for hundreds of miles. In a portion of its course the river came close to the edge of the Cascade Range. The ancient cañon of Lake Chelan had been dammed up by the lava, and a lake occupied a portion of the former bed of the river. The Columbia could not cut its channel deep enough to drain the lake, and there it remained.