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 (Coombs, 1939; Misch, 1966). The present cone was formed
prior to the last major glaciation (Fraser Glaciation), which occurred between
about 25,000 and 10,000 years ago (Armstrong, et.al., 1965; Halstead, 1968;
Heusser, 1974), and probably is considerably older. The cone overlaps rocks of
an earlier eruptive center (Coombs, 1939) from which two radiometric dates of
about 400,000 years have been obtained (Easterbrook and Rahm, 1970). ...
[Map,34K,GIF]
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 (Frank, et.al., 1975), 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 (Coombs, 1939; Frank, et.al., 1975; Bockheim and Ballard, 1975). 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 (Frank, et.al., 1975).
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 (Malone and Frank, 1975). 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 (Malone and Frank, 1975), but no volcanic deposits which could definitely be attributed to historic eruptions were identified during the present investigation.
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