Current Eruption HomePage CVO HomePage Mount St. Helens HomePage Current Update University of Washington Webicorders Eruption Highlights Eruption Chronology Photo Gallery USFS VolcanoCam	[This abbreviated chronology is updated periodically; see Update for daily reports. Time is local: Pacific daylight time until October 31 and Pacific standard time thereafter] Weekly summary report, January 1-January 7, 2005 Seismicity remained at a generally low level. The new dome has segmented itself, and the northerly segment, closest to the vent, is slowly climbing up the back of the southerly segment. This rupture and overriding behavior might have been expected since the southerly part of the dome had stalled against the crater wall. The 1980-86 dome has resumed its slow northerly advance, as indicated by GPS receivers positioned on it. This change is probably a response to the forces exerted on it as the new dome shoulders it way upward. Daily Updates: 1/1, 1/2, 1/3, 1/4, 1/5, 1/6, 1/7 Notable field results from January 3: A new spider, with its GPS receiver HNY-0 (Happy New Year-0), was slung onto the new dome to monitoring the ongoing growth. Gas sampling showed essentially no change, with SO2 and CO2 discharging at rates similar to those seen in December. The chemical analysis of a rock sample collected January 3 showed it to be essentially identical in bulk composition to the hot new dacite collected November 4. Silica content is in the range 65.2-65.3 percent. Hornblende and hypersthene are the dominant visible crystals. However, temperatures inferred from mineral compositions show a wider range than previous samples (from about 850 degrees C to 950 degrees C). The total volume change represented by the welt and dome as of January 3 is 34 million cubic meters (or 44 million cubic yards). For Portlanders, that is equivalent to 134 Rose Garden arenas. The area of the dome and uplift covers about 60 city blocks. In Portland an equivalent area would extend from the Morrison Bridge to the Hawthorne Bridge and from the Willamette River to the Park Blocks. The top of the new lava dome rises about 550 feet above the pre-eruption surface of the flanking glacier. But the lava dome probably extends to the base of the glacier, which means that its true height is closer to 1,100 feet. MSH05_aerial_st_helens_crater_from_east_01-03-05.jpg Aerial view of Mount St. Helens' crater and new dome, from the east. USGS Photograph taken on January 3, by Ken McGee. [medium size] ... [large size] Weekly summary report, January 8-January 14, 2005 Seismicity has been gradually picking up since the low levels of January 2. The increased seismic energy results from an increasing size of small earthquakes, not from a more frequent occurrence of earthquakes. Even so, the seismic record appears "banded," owing to periods of chiefly small events followed by periods with larger events peppered among them. The GPS receiver HNY-0, installed last week on the new dome, has been riding along happily. By January 10 it had traveled 14 m east and 3 m south since the January 3 installation. Its vertical motion was downward 3 m. A rockfall or slab moving off the new dome on Thursday evening, January 14, was imaged by the U.S. Forest Service volcano cam. It showed up brilliantly in the nighttime imagery because the resulting gash exposed rock hotter than the 500-degree Celsius limit for visible incandescence. An accompanying seismic signal was characteristic of rockfalls. An ash plume drifted southward a short distance from the crater, perhaps indicating that a small blast was released by the uncorking effect of the rockfall. For more details, see the eruption-monitoring story, "Things that go bump in the night," elsewhere on our website. Daily Updates: 1/8, 1/9, 1/10, 1/11, 1/12, 1/13, 1/14 Notable field results from January 14: A video camera and gas sensor was installed between the new dome and the 1980-86 domes. The camera sends images every 5 minutes of the north part of the new dome, where extrusion is taking place. A spider containing a GPS receiver and accelerometer was slung onto the new dome, within view of the new camera. A rock sample was collected from within the crater, and an ash sample from the January 13 ash was collected high on the southeast flank. The rock sample is dacite with 65 percent SiO2, similar in composition to the samples of November 4 and January 3, but with texture indicative of slower cooling. Geologists working in the crater were able to observe some low-level venting of both dark and light ash from vents just northwest of the north end of the new dome. The darker ash vented in a sputtering cockscomb-like plume. MSH05_dome_cam_on_opus_01-14-05.jpg Helicopter landing, at "Opus" area of the dome, north of the new dome. The new dome camera/gas sampling station is to the right (above yellow line) underneath helicopter. The GPS/accelerometer spider is just visible as a speck on top of new dome (yellow circle). The area of orange paint splotches on the new dome is within the yellow square. USGS Photograph taken on January 14, 2005, by Dan Dzurisin. [medium size] ... [large size] Weekly summary report, January 15-January 21, 2005 Seismicity continued its slow increase. The remarkable event of the week was the explosive eruption January 16 that scattered ash and ballistics as large as 1 m in the crater and ash eastward onto the volcano's east flank. This event is also described in more detail elsewhere on our website in an eruption-monitoring story, "Things that go bump in the night." The newly installed dome camera and gas sensor were badly damaged during this explosion and remain offline. The new GPS receiver "CDAN," which had been lowered onto the new dome January 14, toppled into oblivion during the explosion. A long-lived GPS receiver, MID-9, also was damaged but continued operating. Its signals, however, are now received only sporadically. Daily Updates: 1/15, 1/16, 1/17, 1/18, 1/19, 1/20, 1/21 Notable field results from January 19: This overflight confirmed the damage reported from the January 16 explosion. Ash from the explosion was collected from the east flank of the volcano on January 19. The ash contains fragments of devitrified dacite, crystals of plagioclase, hypersthene, and hornblende similar to those in the new dome, and more-glassy fragments that may be the new magma (and not just bits of blasted dome carapace). MSH05_dome_opus_area_ballistic_field_01-19-05.jpg Opus area of the dome, looking towards new dome. Ash covering is from event of January 16, 2005. USGS Photograph taken on January 19, 2005, by Dan Dzurisin. [medium size] ... [large size] Weekly summary report, January 22-January 28, 2005 Seismicity has increased very slowly in January from a low reached January 2. It has become steady this week, but still at a level below that of December. This relation is seen in the accompanying graph showing the varying seismic energy at the SHW seismometer since the initial seismic swarm September 23, 2004. The GPS receiver HNY-0, which rides the new dome, has been marching steadily southeastward since its installation January 3. As of January 26, it had moved 60 m east, 15 m south, and 10 m down, for a slope length of 62 m east-southeast. At this rate, it should soon eclipse the 80-m distance record held by ELE-A, the ELEvator GPS receiver that was eaten by the volcano in late November 2004. Daily Updates: 1/22, 1/23, 1/24, 1/25, 1/26, 1/27, 1/28 Notable field results from January 24: The January 24 flight included gas sampling which, while limited by weather conditions, provided SO2 measurements similar to those of early January flights. Ash from the January 16 explosion still mantled the crater floor and an area on the east flank of the volcano, owing to sparse winter rain and snowfall. Hot dacite was continuing to extrude from the vent at the north end of the new dome. The east arm of the crater glacier showed substantial new crevassing and deformation as it is shoved and uplifted by the growing dome. MSH05_glacier_deformation_east_arm_01-24-05.jpg Glacier deformation, east side of Mount St. Helens' dome, as seen from the northeast. USGS Photograph taken on January 24, 2005, by Steve Schilling. [medium size] ... [large size]

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