A BIT OF GEOLOGY

It has been commonly believed that the volcanic action which built up the great cones of the Pacific Coast followed close on the upheavels which produced the Cascade Mountain range -- that the location of the volcanic cones were the weak points in some of the folds through which the subterranean lavas made their exit; thus building up the mighy ash and lava cones of Mt. Baker, Mt. Rainier, Mt. St. Helens, Mt. Adams, Mt. Hood, Mt. Shasta and Mt. Lassen.

From observation in the upper Nisqually valley there is evidence that a long period of time elapsed between movements which elevated the Cascades and the time when the volcanoes were formed. This time was long enough to wear away hundreds of feet of solid rock reducing parts, at least, of the previously formed Cascades to an undulating plateau. It is on top of this plateau that the flows of lava that built Mt. Rainier were poured.

The evidence of this assumption can be seen near the snout of the Nisqually Glacier where the contact of the older Cascade granite and the overlying, younger lavas can be readily seen. The Glacier Trail brings one close to this contact which extends, at intervals, for several miles along the valley wall. For three or four feet directly below the contact the granite is badly weathered and right at the contact there is evidence of an abundance of old soil containing dark, carbonaceous material which represents the plant life of that early age. No determinable fossil remains could be found however. This would tend to show that Mt. Rainier was formed at a much later date than that of the Cascade upheavel.

William L. Effinger, Ranger-Naturalist.