The Cascade Mountains in Oregon have been known since pioneer days as the central part of a volcanic mountain chain extending south-ward into California as far as Lassen Peak, and northward across Washington to Mt. Baker. The rugged nature of the mountains, the heavy timber, and the volcanic rocks combined to render early geological reconnaissance difficult and inconclusive in many respects. It was soon recognized that the Cascade lavas overlie pre-Tertiary rocks in Washington and California, and that the conspicuous peaks are pre-glacial in age, and may have erupted within the last two or three centuries. However, it was by no means known, nor is it yet known, how many geological epochs are represented by the volcanic rocks of the Cascade Mountains, nor how many types of rocks occur, and in what proportions.

Hague and Iddings in 1883 gave the first detailed petrographic description of lavas from . . .

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