TYPICAL GLACIAL VALLEY WITH CHAIN OF ROCK-BASIN LAKES. GLENN AND CROSSLEY LAKES IN DISTANCE; UNNAMED LAKE IN FOREGROUND RESTS IN A HANGING VALLEY AND ITS OUTLET DROPS SEVERAL HUNDRED FEET TO THE MAIN VALLEY (HILEMAN PHOTO)
The tributaries of glacial valleys are also peculiar in that they usually enter the main valley high above its floor and for this reason are known as hanging valleys. The thicker a stream of ice, the more erosion it is capable of performing; consequently, the main valley becomes greatly deepened, whereas the smaller glacier in the tributary valley does not cut down so rapidly, leaving its valley hanging high above the floor of the major valley. The valleys of Virginia and Florence Creeks, tributary to the St. Mary Valley are excellent examples of hanging valleys. A splendid view of Virginia Creek valley may be had from Going-to-the-Sun Road near the head of St. Mary Lake. The valley above Bird Woman Falls as seen from Going-to-the-Sun Road just west of Logan Pass is a spectacular illustration of a hanging valley. In addition there are many others, such as Preston Park, on the trail from St. Mary to Piegan Pass; and the Hanging Gardens near Logan Pass.
REYNOLDS MOUNTAIN AT LOGAN PASS—A TYPICAL HORN
Even more conspicuous than the large U-shaped valleys and their hanging tributaries are the long, sharp-crested, jagged ridges which form most of the backbone of the Lewis Range. These features of which the Garden Wall is one of the most noticeable, are known as aretes and owe their origin to glaciers. As the former long valley glaciers enlarged their cirques by cutting farther in toward the center of the range, the latter finally was reduced to a very narrow steep-sided ridge, the arete. The imposing height of the Garden Wall can readily be determined by using the layer of diorite as a scale. The conspicuous black band formed by the edge of this layer has an average width of 75 feet. So, from the porch of the Many Glacier Hotel a Park visitor can readily see that the Garden Wall, even though five miles distant, is about 4,200 feet high. The height of other aretes can be just as readily obtained, for the band of diorite appears on the faces of most of them. In certain places glaciers on opposite sides of the arete nearly cut through creating a low place known as a col, usually called a pass. Gunsight, Logan, Red Eagle, Stoney Indian and Piegan are only a few of the many such passes in the Park. At places three or more glaciers plucked their way back toward a common point leaving at their heads a conspicuous, sharp-pointed peak known as a horn. Innumerable such horn peaks occur throughout both the Lewis and Livingstone Ranges. Excellent examples near Logan Pass are Reynolds, Bearhat, and Clements Mountains. Other imposing horns are Split Mountain at the head of Red Eagle Valley, Kinnerly Peak in the Kintla Valley, and Mount Wilbur in Swiftcurrent Valley. The horn peak, because of its precipitous sides, is especially attractive to mountain climbers. The comparatively recent dates of first ascents on many Park peaks attest to the difficulties they offer the mountaineer. Mount Wilbur, despite proximity to Many Glacier Hotel and camp, was unclimbed until 1923; Mount St. Nicholas succumbed in 1926, and the first ascent of Kinnerly Peak was made by several members of the Sierra Club in 1937.
Another feature of the Park which must be attributed partly to glaciation is the waterfall. There are two principal types, one which occurs in the bottom of the main valleys and one at the mouth of the hanging tributary valleys. The former, exemplified by Swiftcurrent, Red Rock, Dawn Mist, Trick, Morning Eagle and others, is located where streams drop over the risers of the glacial stairway. In other words, resistant layers of rock which the former glaciers were unable to entirely wear away give rise to this type of fall.
Examples of the hanging tributary type of fall which is due directly to the activity of the glaciers are Florence, Bird Woman, Virginia, Grinnell, Lincoln, and many others.
TRICK FALLS IN THE TWO MEDICINE RIVER