Mount Baker is a large stratovolcano in northwestern Washington about 30 kilometers east of Bellingham and 25 kilometers south of the International Boundary. The glacier-covered cone of andesite lava flows and breccias rises 2 kilometers above adjacent mountains carved from a complex of older sedimentary and metamorphic rocks. The present cone was formed prior to the last major glaciation, which occurred between about 25,000 and 10,000 years ago, and probably is considerably older. The cone overlaps rocks of an earlier eruptive center from which two radiometric dates of about 400,000 years have been obtained. ...
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Mount Baker is drained on the north by streams flowing into the North Fork Nooksack River, on the west by the Middle Fork Nooksack River, and on the southeast and east by tributaries of the Baker River, which empties into the Skagit River about 14 kilometers southeast of Mount Baker. The Baker River is impounded by two dams; the upper dam is near the mouth of the Sulphur Creek valley and forms Baker Lake, and the lower dam is about 12 kilometers farther downvalley and forms Lake Shannon.
Mount Baker's summit crater is covered by snow and ice, and little is known of its nature or age. A prominent crater partly filled with ice, known as Sherman Crater, is 350 meters lower than, and about 800 meters south of, the summit. Its east rim, above the head of Boulder Glacier, is breached by a notch about 150 meters deep. Another low point, about 100 meters deep, is on the southwest rim above Deming Glacier. Fumaroles and thermal springs are concentrated in the crater, where solfataric and hydrothermal activity has produced clay minerals and other alteration products. Avalanches of snow, firn, and hydrothermally altered rock debris from the rim of Sherman Crater have swept down Boulder Glacier at least six times since 1958.
Most hydrothermal activity at Mount Baker is concentrated within Sherman Crater, although a small area of fumaroles, known as the Dorr Fumarole Field, is present on the north flank of the volcano at an altitude of 2,300 to 3,500 meters. The activity at Sherman Crater increased significantly in March 1975 and caused concern that an eruption might be imminent. As a result, various kinds of geophysical and geochemical monitoring were undertaken in the expectation that if an eruption occurred it would be preceded by other kinds of events. ...
Mount Baker was active on several occasions during the 19th century, but no volcanic deposits which could definitely be attributed to historic eruptions were identified during the present investigation.
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