Crater Lake, situated close to the crest of the Cascades of southern Oregon, approximately in latitude 43° N, longitude 122° W, occupies an extensive crater, formed by the destruction of a mountain, which has been named Mount Mazama. The lake lies at an altitude of 6161 feet, approximately 16 feet lower than that recorded by early surveys, and is surrounded by a nearly circular rim, varying from 500 to 2,000 feet in height (Pl. 1, fig. 1). It has a shoreline of approximately 21 miles and is 6½ miles in diameter from west to east and about 4½ miles from north to south. The materials in the crater walls and the inclination of the back slopes indicate that, prior to the formation of the lake, there was a composite cone, 12,000 to 15,000 feet high, with a circumference comparable to that of Mount Shasta (Fig. 1).
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