GEOLOGY OF MOUNT RAINIER

Mount Rainier is an old volcano, not dead, merely dormant, one of a series of volcanic cones that extend clear around the Pacific Ocean. It was built up by its own action, that is, by successive lava flows intermittant with more explosive eruptions that threw out great quantities of pumice, cinders, and other volcanic ash. At one time, the cone reached an elevation of sixteen or seventeen thousand feet. At a later date, during a series of very violent erruptions, some two or three thousand feet were carried away leaving a crater on top about three miles across.

The rim of this old crater, except for two points, peak Success and Liberty Cap has been broken down by the action of the ice which has cut at least one thousand feet from the surface of the peak.

Inside this old crater, at a comparatively recent date, a small cinder cone was built up on top of which there are at present two distinct craters a half mile across and almost circular. The rims of the craters area kept free of snow by high winds and residual heat. A great deal of steam and other hot gasses are constantly escaping from vents around the rim.

Of the twenty-eight glaciers which are at work on the peak, seven start directly from the cap of snow which lies a hundred or more feet deep around the summit. The glaciers have cut great canyons for themselves, leaving the cone fluted like a mamoth stump with protruding roots.

At this time of year, when, because of the warm days, the snow is melting and the glaciers are beginning to move more rapidly, this tearing down process is at its maximum.

All of the rivers flowing from under glaciers are filled to overflowing with turbulent, rock filled, water.

It has been estimated that such of the larger streams carry from 500 to 700 tons of finely powdered rock away from the mountain each twenty-four hours.

Mount Rainier, the by far the greatest peak within the United States, because of the fact that it stands alone and rises almost directly from sea-level, is probably being torn down faster than any other mountain peak on the continent. However, it still contains more than one hundred and fifty cubic miles of material and will no doubt stand several years yet.