Mount Baker dominates the skyline from Bellingham, Washington, and Vanc
ouver, British Columbia. On cold, clear winter days, dramatic increases in the steam plume rising continuously from Sherman Crater can alarm local residents. This apparent increase in plume vigor occurs because of condensation of steam in cold, calm air. In 1975, however, increased steaming and melting of snow and ice around Sherman Crater did signify a change in heat output from the volcano's interior. Although the increased heat flow gradually subsided, it could have signaled the start of eruptive activity, and precautions were wisely undertaken. So that the public can be warned of, and be prepared for, future eruptions and other hazardous events at Mount Baker, U.S. Geological Survey (USGS) scientists are studying the volcano's past behavior and monitoring its current activity.
Modern Mount Baker formed during and since the last ice age, which ended about 15,000 years ago. Lava flows from the summit vent erupted between 30,000 and 10,000 years ago and, during the final stages of edifice construction, blocky pyroclastic flows poured down most of the volcano's drainages. An eruption 6,600 years ago produced a blanket of ash that extended more than 20 miles to the northeast. This eruption probably occurred from the presently ice-filled summit crater. Subsequently, sulfurous gases have found two pathways to the surface— Dorr Fumaroles, northeast of the summit, and Sherman Crater, south of the summit. Both these area are sites of pervasive bedrock alteration, converting lavas to weak, white-to-yellow material rich in clays, silica, and sulfur-bearing minerals. At Sherman Crater, collapses of this weakened rock created lahars in 1843 and as recently as the 1970's.
ouver, British Columbia. On cold, clear winter days, dramatic increases in the steam plume rising continuously from Sherman Crater can alarm local residents. This apparent increase in plume vigor occurs because of condensation of steam in cold, calm air. In 1975, however, increased steaming and melting of snow and ice around Sherman Crater did signify a change in heat output from the volcano's interior. Although the increased heat flow gradually subsided, it could have signaled the start of eruptive activity, and precautions were wisely undertaken. So that the public can be warned of, and be prepared for, future eruptions and other hazardous events at Mount Baker, U.S. Geological Survey (USGS) scientists are studying the volcano's past behavior and monitoring its current activity.Modern Mount Baker formed during and since the last ice age, which ended about 15,000 years ago. Lava flows from the summit vent erupted between 30,000 and 10,000 years ago and, during the final stages of edifice construction, blocky pyroclastic flows poured down most of the volcano's drainages. An eruption 6,600 years ago produced a blanket of ash that extended more than 20 miles to the northeast. This eruption probably occurred from the presently ice-filled summit crater. Subsequently, sulfurous gases have found two pathways to the surface— Dorr Fumaroles, northeast of the summit, and Sherman Crater, south of the summit. Both these area are sites of pervasive bedrock alteration, converting lavas to weak, white-to-yellow material rich in clays, silica, and sulfur-bearing minerals. At Sherman Crater, collapses of this weakened rock created lahars in 1843 and as recently as the 1970's.
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