Continued high fumarolic activity; clusters of hundred of new fumaroles

Card 2244 (07 August 1975) Continued high fumarolic activity; clusters of hundred of new fumaroles

All available evidence shows that the March increase in fumarolic activity at Mount Baker has not diminished and in some aspects has continued to increase. Since the initial ground investigation on 28 March, various university and federal scientists have installed instrumentation to begin intensive volcano monitoring.

Clusters of hundreds of new fumaroles have at least doubled the area of snow-free ground and have melted large ice pits in the normally glacier-filled Sherman Crater. Two of the new ice pits contain shallow lakes, one of which was 34°C on 11 June. Acid water from the lakes and from other snowmelt in the crater drains into the Boulder Creek valley on the east side of the volcano where water quality is presently monitored.

As ice cover in the crater melts, new clusters of fumaroles continue to appear. One main fumarole which was about 1 m in diameter in March has developed into a 1 x 5 m fissure. Accessible fumaroles have had temperatures at boiling, 90-91°C; but the main fumarole remains inaccessible. Continual ash emission from this as well as some of the other fumaroles has coated snow in the Sherman Crater area with a gray blanket at least 1 cm thick. Several analyses of the ash show it to be composed largely of secondary minerals, old rock fragments, and pyrite-covered sulfur droplets. A very small fraction of vesicular glass in some ash samples is currently thought to be reworked older material.

Continuously-telemetered seismic data from a station on the Sherman Crater rim and from a station at a lower elevation show intermittent variations in high-frequency background noise and a few local transient seismic events. No strong seismic trend has yet been detected. Furthermore, a hydrogen and temperature sensor, several tilt and gravity stations, and time-lapse cameras have not been in operation long enough to show definite trends. Additional monitoring includes aerial photographic, thermographic, and sulfur surveys.

The other large thermal area on Mount Baker, the Dorr fumarole field on the N side of the cone, has not yet shown significant changes in activity compared to previous years.

Information Contacts: David Frank, Quaternary Research Center, University of Washington; Stephen D. Malone, University of Washington.

Information is preliminary and subject to change. All times are local (unless otherwise noted)

March 1975 (CSLP 26-75)

Increased fumarolic activity and new fumaroles

Card 2132 (28 March 1975) Increased fumarolic activity and new fumaroles

Reports were received beginning on the evening of 10 March 1975, of larger than normal amounts of vapor from Sherman Crater, which is known to have contained a fumarole field since the latter 1800's. Aerial photographs taken 11 March show two new clusters of fumaroles which perforate through snow and ice in Sherman Crater. Semi-circular crevasses in the crater were apparent and seemed to be related to ice subsidence.

A thin swath of gray debris, partly covered by new snow, extended 100-300 m outside the E, S, and W part of the crater rim. A small lake within one of the ice perforations was observed by air on 11 and 13 March. On 20 March, ground observers examined Boulder Creek, down valley from the drainage outlet of the Sherman Crater rim and reported no flooding but highly acidic (pH = 3.7) and sulfur-smelling water. Large amounts of steam were seen when the mountain again was visible on 24 March.

An interdisciplinary team of scientists is mobilizing to determine the significance of the new thermal activity.

Information Contacts: David Frank, University of Washington; Mark F. Miller, USGS.

July 1975 (CSLP 26-75)

New crater lake observed; significant melting

Card 2219 (14 July 1975) Aerial observations; new crater lake

A photo flight under dull, high overcast was made between 1500 and 1530 over Mt. Baker on 3 July 1975. Vertical photos with a K-17, 6" lens of Sherman Crater, Dorr Fumarole Field and later, McAllister, Klawatti, Boston, and South Cascade glaciers, plus numerous 35 mm oblique color views were taken.

Steam activity at the fumarole sites including Dorr Fumraole Field was the lowest we have observed in recent months, possibly due to atmospheric conditions. This allowed a close examination of many openings, particularly the E breach area of the crater, and here a new crater lake was observed in a large ice cavern located NE of the central pit about midway between the E breach and the N pit. The lake color was a muddy brown, in contrast to the pale green of the central lake. It appeared to be at least 20 m across, and of undetermined length. Most of the ice bridge covering the new lake appeared to be quite thick and ice encroaching from the N slope may delay its collapse for weeks or even months.

No new large openings were observed in the E breach area where the snow was completely covered with a heavy, continuous layer of brown/gray mud. The ice was melting away from the rocks on either side exposing openings which appeared to connect with the subglacial opening following the outlet stream, possibly due to thermal heat in the rocks. A crevasse near the head of Boulder Glacier, which probably spans the subglacial outlet stream from the crater, appeared to open into an extensive cavern below. No steam was observed from this potentially large opening.

Card 2227 (21 July 1975) Rapid melting of ice and snow

A photo flight with clear skies was made between 1530 and 1600 over Mt. Baker on 9 July 1975. The temperature at 4,000 m was +10°C and extremely rapid snow and ice melt was in progress; Glacier Creek in particular was a brown, raging flood. The effects of snow melt were very noticeable on the upper part of the mountain, seasonal snow having disappeared from most rock areas and last year's snow surface being exposed on areas subject to wind scour. Other evidence of very thin snow on the upper mountain was the reappearance of traces of the rim of the true Summit Crater in the Roman Wall vicinity, a feature which has been snow-covered when photographed later than in the 1940's.

In the six days since observing the mountain, changes in the Sherman Crater area were notable. Fragments of ice falling into the central pit covered most of the bottom and these either filled most of the lake or the lake had largely drained. The new lake observed 3 July was completely obscured by collapse of the entrance of the ice cavern in which it was located. No doubt due in part to the very rapid surface melting in progress, rocks within the crater recently exposed by sliding of the ice off the slopes were much more visible.

The most noteworthy change outside the crater was the collapse of the ice covering a cavity noted in a crevasse near the head of Boulder Glacier observed on 3 July. More important, although visible steam activity within the crater was low as on 3 July and the Dorr Fumarole Field was notable by a nearly complete absence of visible steam, fog-like vapor was observed in the highest crevasse on Boulder Glacier near the area of ice collapse. These together strongly suggest that a fumarole has developed in this critical area situated immediately below Sherman Peak and Lahar Lookout.

Information Contacts:
Card 2219 (14 July 1975) Austin Post, USGS.
Card 2227 (21 July 1975) Austin Post, USGS.

August 1975 (CSLP 26-75)

Continued high fumarolic activity; clusters of hundred of new fumaroles

Card 2244 (07 August 1975) Continued high fumarolic activity; clusters of hundred of new fumaroles

All available evidence shows that the March increase in fumarolic activity at Mount Baker has not diminished and in some aspects has continued to increase. Since the initial ground investigation on 28 March, various university and federal scientists have installed instrumentation to begin intensive volcano monitoring.

Clusters of hundreds of new fumaroles have at least doubled the area of snow-free ground and have melted large ice pits in the normally glacier-filled Sherman Crater. Two of the new ice pits contain shallow lakes, one of which was 34°C on 11 June. Acid water from the lakes and from other snowmelt in the crater drains into the Boulder Creek valley on the east side of the volcano where water quality is presently monitored.

As ice cover in the crater melts, new clusters of fumaroles continue to appear. One main fumarole which was about 1 m in diameter in March has developed into a 1 x 5 m fissure. Accessible fumaroles have had temperatures at boiling, 90-91°C; but the main fumarole remains inaccessible. Continual ash emission from this as well as some of the other fumaroles has coated snow in the Sherman Crater area with a gray blanket at least 1 cm thick. Several analyses of the ash show it to be composed largely of secondary minerals, old rock fragments, and pyrite-covered sulfur droplets. A very small fraction of vesicular glass in some ash samples is currently thought to be reworked older material.

Continuously-telemetered seismic data from a station on the Sherman Crater rim and from a station at a lower elevation show intermittent variations in high-frequency background noise and a few local transient seismic events. No strong seismic trend has yet been detected. Furthermore, a hydrogen and temperature sensor, several tilt and gravity stations, and time-lapse cameras have not been in operation long enough to show definite trends. Additional monitoring includes aerial photographic, thermographic, and sulfur surveys.

The other large thermal area on Mount Baker, the Dorr fumarole field on the N side of the cone, has not yet shown significant changes in activity compared to previous years.

Information Contacts: David Frank, Quaternary Research Center, University of Washington; Stephen D. Malone, University of Washington.