CVO Menu - Mount St. Helens Eruption 2004 - Eruption Chronology, September 23, through October 14, 2004

USGS/Cascades Volcano Observatory, Vancouver, Washington

Mount St. Helens, Washington
2004 Eruption Chronology
September 23 through October 14, 2004

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[This abbreviated chronology is updated periodically; see Update for daily reports. The first 22 days are reported sequentially herein. Thereafter the reports are weekly summaries. Time is local: Pacific daylight time until October 31 and Pacific standard time thereafter]

The first 22 days:
September 23 through October 14, 2004 Summary:

Day 1: September 23, unrest began, heralded by a swarm of small earthquakes.
Day 7: September 29, deformation of the crater floor was recognized.
Day 9: October 1, first emission of steam and ash occurred.
Day 10: October 2, first episode of sustained tremor.
Day 12: October 4, large-scale uplift had deformed the crater floor.
Day 15: October 7, first notable SO2, released at the rate of 100 tons per day.
Day 19: October 11, new dome breached the surface, recognized when freshly extruded rock formed a "fin" abreast the uplifted crater floor.

DAY 1-3:
Thursday-Saturday, September 23-25, 2004:

A swarm of small, shallow earthquakes (smaller than magnitude 1) began on morning of September 23, peaked in midday on September 24, then declined through the afternoon of September 25.
Mount St. Helens Information Statement issued September 24, 2004, at 10:00 PDT.
Daily Updates: 9/23, 9/24, 9/25

DAY 4:
Sunday, September 26, 2004:

Seismicity increased, including 10 events ranging in magnitude from 2 to 2.8. An official Notice of Volcanic Unrest was issued by the Cascades Volcano Observatory (CVO) at 3:00 p.m., the first since October 1986. Alert Level was 1, "Code Yellow."
Daily Update: 9/26

MSH04_crater_dome_aerial_9-26-04_B.jpg
Oblique aerial photograph of north flank, crater, lava dome and new glacier (behind dome), Mount St. Helens, Washington state, USA.
USGS photograph taken on 26 September, 2004 by John S. Pallister.
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DAY 5:
Monday, September 27, 2004:

No anomalous gas emissions were detected during a gas-monitoring helicopter flight around the 1980-86 dome in the Mount St. Helens crater.
Newly crevassed ice seen on glacier south of dome.
Daily Update: 9/27

MSH04_aerial_crater_dome_from_NW_9-27-04.jpg
Western side of Mount St. Helens crater and dome, showing west side of the dome.
USGS photograph taken on 27 September 2004 by Steve Schilling.
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DAY 6:
Tuesday, September 28, 2004:

Daily Update: 9/28

MSH04_crater_dome_from_sugarbowl_9-28-04.jpg
Mount St. Helens crater and dome as seen from SugarBowl, on the NE flank of the volcano.
USGS photograph taken on 28 September 2004 by Mike Poland and Dan Dzurisin.
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DAY 7:
Wednesday, September 29, 2004:

Seismicity increased substantially overnight and into the wee hours of September 29. Earthquakes occurred at the rate of four per minute. The largest events approached M 2.5 and became more frequent. All earthquakes originated at shallow levels in and below the 1980-86 lava dome.
At 10:40 a.m., CVO issued a Volcano Advisory--Alert Level 2, "Code Orange."
Overflights found deformation on the crater floor south of the 1980-86 dome.
Daily Update: 9/29

MSH04_dome_glacier_from_east_9-29-04.jpg
South side of Mount St. Helens lava dome, as seen from the east, showing the dome and part of the glacier forming at the base of the dome.
USGS photograph taken on 29 September 2004 by Mike Poland and Dan Dzurisin.
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DAY 8:
Thursday, September 30, 2004:

The area of deformation seen September 29 was more precisely estimated from oblique aerial photographs. It encompassed 20,000-40,000 square meters (5-10 acres). Amount of uplift totaled several meters. New fissures had cut across ice and talus lying upon glacial ice.
Daily Update: 9/30

MSH04_dome_glacier_closein_south_side_9-30-04.jpg
Closer-in view of south side of Mount St. Helens lava dome, showing the dome and part of the glacier forming at the base of the dome.
USGS photograph taken on 30 September 2004 by Mike Poland and Dan Dzurisin.
[medium size] ... [large size]

DAY 9:
Friday, October 1, 2004:

Thermal measurements made with forward-looking infrared (FLIR) camera showed only low-temperature rock surfaces.
Beginning at 11:57 a.m. and lasting about 25 minutes, a small steam eruption, with minor ash, issued from a vent just south of the 1980-86 lava dome, the culmination of a week of increasingly energetic seismicity. This vent lay within that part of the crater-floor glacier that had become increasingly crevassed and uplifted over the past few days. The plume rose to 3,700 m altitude (12,000 ft), dropped to 3,000 m (10,000 ft), and drifted southwest with minor ashfall close to the volcano.
A seismic station and GPS receiver on the 1980-86 dome were destroyed by ballistics propelled by this eruption.
Seismicity dropped to a low level for several hours after the eruption, then gradually increased. Largest earthquake was M3.5. Helicopter gas-monitoring flight detected no magmatic gases in the area of the new vent, but a strong CO2 signal was detected from a new small fumarole on the northwest face of the 1980-86 dome.
Alert level remained at Volcano Advisory.
Daily Update: 10/1

MSH04_crater_eruption_image_120332PDT_10-01-04.jpg
Crater/Plume image, Mount St. Helens.
USGS photograph taken at 12:03:32 PDT on October 1, 2004, by John Pallister
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DAY 10:
Saturday, October 2, 2004:

At 12:15 p.m., a small steam emission lasted for 1-2 minutes. Immediately following it, seismic activity changed from principally rock-breakage events to continuous low-frequency tremor that lasted 50 minutes.
At 2:00 p.m., CVO issued a Volcano Alert (Alert Level 3, "Code Red"). The U.S. Forest Service evacuated its visitor center at Johnston Ridge, which lies 8 km north-northwest of the volcano. (The Johnston Ridge Observatory has remained closed since October 2).
An afternoon gas-monitoring flight detected an increase in the number of fumaroles on the 1980-86 lava dome. CO2 was again detected, this time with the intermittent smell of H2S (a substantial change from previous day). The FLIR infrared camera found no thermal anomalies.
Daily Update: 10/2

MSH04_dome_glacier_south_side_10-02-04.jpg
South side of Mount St. Helens lava dome, showing the dome and part of the glacier forming at the base of the dome.
USGS photograph taken on 2 October 2004 by Mike Poland.
[medium size] ... [large size]

DAY 11:
Sunday, October 3, 2004:

At 2:57 a.m., an episode of low-frequency tremor persisted for 25 minutes. No eruptive plume was detected.
Gas monitoring again detected CO2 and low levels of H2S but no SO2. Visual observations suggested the crater floor had been uplifted tens of meters. This deformation was localized within the crater; no significant changes were detected on the outer GPS net.
At 10:40 p.m., a small steam (and possibly ash) eruption occurred. Its plume, visible in the moonlight, barely reached to the crater rim (altitude 2,550 m; 8,360 ft).
The FAA issued a Notice to Airmen (notam), imposing a temporary flight restriction within 9 km (5 naut. mi) radius of Mount St. Helen's summit and below about 4,600 m altitude (15,000 ft, officially) .
Daily Update: 10/3

MSH04_dome_glacier_uplift_closein_from_east_10-03-04.jpg
Mount St. Helens dome and glacier uplift from the east.
USGS photograph taken on October 3, 2004, by Steve Schilling.
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DAY 12:
Monday, October 4, 2004:

Large-scale uplift, on the order of tens of meters, was verified on the basis of visual observations and photogrammetric analysis from the previous day. Deformation affected part of the crater-floor glacier and adjacent area of the 1980-86 dome.
At 9:43 a.m., a small steam and ash eruption occurred, lasting 40 minutes. Associated seismicity was trifling. The steam plume reached to about 3,700 m (12,000 ft) altitude, and its ashy fallout dusted roads southeast of the volcano. Ash thickness at 8 km (5 mi) from the volcano was 0.2 cm (less than one-eighth inch)
A gas-monitoring flight again detected CO2 and H2S, but no SO2.
Two additional GPS receivers were lowered onto the 1980-86 dome to aid in measuring its deformation.
At 2:10 p.m., another period of smaller steam and ash bursts began, lasting about 30 minutes.
Daily Update: 10/4

MSH04_dome_from_east_10-04-04.jpg
USGS photograph taken on October 4, 2004.
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DAY 13:
Tuesday, October 5, 2004:

9:03 a.m. marked the beginning of the most vigorous steam-and-ash eruption since the start of unrest. It lasted over one hour. The ash rose to about 3,700 m (12,000 ft) and drifted north-northeastward. A light ash dusting fell in the towns of Morton, Randle, and Packwood, about 50 km (30 mi) away. A light dusting affected the east side of Mount Rainier National Park, 110 km (70 mi) north-northeast.
Seismicity diminished after the small eruption. GPS sites on dome survived event; trend of northward displacement (several centimeters) continued. A broadband seismometer with satellite-linked telemetry was installed on the northwest flank of the 1980-86 dome.
A new vent was observed in same deformed area south of the 1980-86 dome.
Daily Update: 10/5

MSH04_crater_rim_plume_0956PDT_10-05-04.jpg
Aerial view of Mount St. Helens' crater rim and recent plume.
USGS Photograph taken on 5 October 2004 at 09:56:05 PDT, by Steve Schilling.
[medium size] ... [large size] ... [print ready]

DAY 14:
Wednesday, October 6, 2004:

During the morning, weak steam plumes from crater were observed briefly. Seismicity, including tremor, remained low after the previous day's eruption.
At 9:15 a.m., CVO lowered the alert level to Volcano Advisory (Alert level 2, "Code Orange").
Top of the area of intense uplift was at about same height as the highest point of the 1980-86 lava dome.
Daily Update: 10/6

MSH04_dome_glacier_uplift_10-06-04.jpg
View from the east side of Mount St. Helens dome looking at the uplift of the glacier and south flank of the lava dome.
USGS Photograph taken on 6 October 2004 at 17:26:24 PDT, by John Pallister.
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DAY 15:
Thursday, October 7, 2004:

Seismicity persisted at low to moderate rate (1-2 events per minute).
Brief observations of crater revealed only weak puffs of steam from vents.
New vigorous vent reported. A gas-monitoring flight measured emission rates of 2,400 tons per day CO2 and 100 tons per day SO2, the first significant SO2 concentrations of the eruption. The emission rate for H2S was 10 tons per day.

MSH04_dome_glacier_uplift_from_east_10-07-04.jpg
View from the east side of Mount St. Helens lava dome looking at the lava dome (right) and the uplift of the glacier and south flank of the lava dome (left).
USGS Photograph taken on 7 October 2004 by Dan Dzurisin.
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DAY 16:
Friday, October 8, 2004:

Seismicity increased gradually from the low rate of the past few days, reaching counts of 1-2 events per minute. The largest earthquake registered M 2.4.

DAY 17:
Saturday, October 9, 2004:

Seismicity persisted at moderate but variable rate.
No visual observations were possible, owing to low clouds and rain.

Recent photography and LIDAR imagery indicated an uplifted area of 400 m (1,300 ft) in north-south dimension and 480 m (1,600 ft) in east-west dimension. Maximum uplift was 100-120 m (330-400 ft). [The published Update (Oct 9, 5:30 p.m.) describing these numbers offered an estimated "rate of volume increase" of roughly 2 million cubic meters per day (2.6 million cubic yd), on average, for the time from late September to October 6, 2004. (The deformed volume was thought to be 16 million cubic meters.) Subsequent measurements using more precise methodology found smaller total volume and corresponding rates of only 0.7-0.8 million cubic meters per day.]

DAY 18:
Sunday, October 10, 2004:

Seismic activity decreased to the low level that was characteristic of the evening of October 7--one event per minute and M 1.0 or less.
The deforming area had increased by about 10 percent since last seen on October 7.
Minor ash emissions occurred during the night, as indicated by a dusting of ash on snow seen on October 11.

MSH04_aerial_crater_dome_steam_from_NE_10-10-04.jpg
Mount St. Helens crater and dome as seen from the northeast.
USGS Photograph taken on 10 October 2004, by Jim Vallance.
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DAY 19:
Monday, October 11, 2004:

Seismic activity continued at low level (1 event per 5-10 min; M1 or smaller).
Steam plume from deforming area continued to rise to just above crater. Steam and ash were emitted briefly from western part of uplifted at about 4:00 p.m., drifting southeastward.
During an afternoon overflight, a "fin" or slab of pinkish-gray rock (~30 m high by 60 m long) was observed in uplifted area; FLIR reading indicated surface temperature of 500-600 degrees Celsius (900-1,100 deg Fahrenheit), suggesting FIRST APPEARANCE OF EXTRUDED MAGMATIC MATERIAL IN CRATER.
Gas flight recorded 1,100 tons per day CO2, 70 tons per day SO2, and 6 tons per day H2S (decreased from 4 days earlier).

MSH04_dome_uplift_closein_from_west_10-11-04.jpg
Mount St. Helens dome and uplift from the west.
USGS Photograph taken on 11 October 2004, by Jon Major.
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DAY 20:
Tuesday, October 12, 2004:

Visual observations were hampered by steam clouds. The area of high-temperature new dome rock ("the fin") appeared to have grown somewhat; FLIR infrared camera recorded surface temperatures of ~700 degrees Celsius (1,300 degrees Fahrenheit) in this area.
A new instrument package (BLIS) with seismometer, GPS, tiltmeters, and microphone was deployed by helicopter on east side of uplifted area; regrettably, its GPS antenna was damaged during deployment.
Seismicity persisted at low level, primarily as low-frequency events.
Thermal anomalies were seen for first time in NOAA satellite imagery (2-3 pixels=5-10 degrees Celsius above background).

MSH04_preparing_BLIS_for_dome_10-12-04.jpg
USGS scientists do last minute preparations for slinging the BLIS instruments to the dome. The instrument package consists of a high and low-gain accelerometer (seismometer) and a microphone. All are named "BLIS" (Blister).
USGS Photograph taken on 12 October 2004.
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DAY 21:
Wednesday, October 13, 2004:

Slow extrusion, with increased areas of both the uplift and the new feature (fin); abundant steaming.
Low seismic activity.
FLIR surface temperature of almost 700 degrees Celsius measured in parts of new lobe.
Gas flight indicated no CO2, and low SO2 and H2S.

MSH04_dome_uplift_from_southeast_10-13-04.jpg
Mount St. Helens dome and uplift with new growth, as seen from the southeast.
USGS Photograph taken on 13 October 2004, by Kathy Cashman.
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DAY 22:
Thursday, October 14, 2004:

Same basic observations as previous day.

MSH04_new_growth_with_avalanche_fan_10-14-04.jpg
Mount St. Helens uplift with new growth and new avalanche fan, as seen from the west.
USGS Photograph taken on 14 October 2004, by Jim Vallance.
[medium size] ... [large size] ... [print ready]

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12/06/04, Lyn Topinka