GEOLOGICAL STORY OF "THE MOUNTAIN"

The peaceful Pacific - so called - is encircled by a series of volcanic peaks from the Aleutian Islands to the north, down either side of the great sea to Mt. Erebus near the South Pole. Many of these are active while others have been dead or dormant for centuries -- only their great cones which loom above the surrounding country standing as monuments to Nature's power in her wildest moods. Mt. Rainier is one of these, being built by succeeding eruptions in times past, but now regarded as dead. Yet there are warm springs at its base and steam and sulphur gases arise from within the rim of the snow filled crater at the summit.

At one time in past ages (see Diagram "A") the region which is now Mt. Rainier Nat'l Park was composed of a series of rather low, granite ridges. Then through a weak point in the earth's crust the first lavas flowed (see Diagram "B"), gradually lava flows accounts, in a measure, for the tread base of Mt. Rainier -- a base which covers 100 square miles in area -- for their viscuous character caused them to spread out over a wide area. Later on more explosive material was embodied in its outbursts and this material, blown high in the air, cooled rapidly and upon falling to earth built a cone of steeper contour which, scientists tell us, was approximately 2000 feet higher that the summit of the "Mountain" today (see Diagram "C"). Then during some violent eruption the upper portion of the cone was destroyed, exposing a giant caldera about three miles across, so that Rainier today from certain angles appears like a huge stump (see Diagram "D"). Later and feebler eruptions built a minor crater within the caldera and it is from its rim that the present steam and gases arise.

But as succeeding eruptions increased the altitude of "The Mountain" the moisture laden winds sweeping in from the Pacific dropped their moisture in the form of snow upon its broad slopes -- giving rise to the glacial system that at one time extended down beyond the Mountain to meet the Puget Sound lobe of the great Ice Cap that had advanced from the north. With the recession of the ice cap the glaciers of the entire region, including those of Mt. Rainier, receeded also until today they are but remnants of their former selves. Those of Mt. Rainier remain outstanding largely because of the continued and excessive snowfall upon its flanks.

But as "The Mountain" was built by fire it is being gradually torn apart by the opposing force -- water, in the form of glacial ice. The glaciers as they move slowly downward dig deep canyons, stripping the "Mountain" of its outer lavas until today, instead of a smooth, symetrical cone we find a rugged peak whose flanks are seamed with great gorges, many of which hold glaciers that are even yet continuing their work of grinding the ground up particles away toward Puget Sound via the rushing mountain streams that originate at the snouts of these glaciers. It has been estimated that fifty cubic miles of material has been cut and carried away from the slopes of Mt. Rainier in past years by these glaciers -- needless to say such action has left a visible impression to the power of this moving ice.

MT RAINIER'S GLACIERS

Twenty eight glaciers are included in the glacial system of this mountain -- it is considered the greatest glacial system radiating from a single peak in the United States, and when we consider that the ice area on "The Mountain" is about 45 square miles we can easily understand why it has this distinctive. Of the twenty eight glaciers, six originate from the neve field at the summit and are thus termed "primary" glaciers. Many of them too, are "live" -- that is they move slowly down the mountainside. However the melting at the snout is greater than the movement downward and as a matter of fact they are gradually losing ground -- receeding. This is illustrated in the case of the Nisqually whose recession has been tabulated for a period of years. It shows that, in spite of the downward movement, the Nisqually Glacier actually receeds on the average of 40 feet per year. From October 1927 to October 1928 it lost 89 feet. While six of these glaciers originate from the neve field the majority have their source at about 10,000 or 11,000 feet in elevation in great cirques, or bowls that have been carved out by these glaciers. Such is the origin of the Carbon Glacier -- the one that extends farther down upon the slopes of the "Mountain" than any other.

The Emmons Glacier in the White River district is the largest on Mt. Rainier and of course the largest in the United States. It is one and one half miles wide at its widest point and approximately five and one half miles long.

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