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385:, and 721 feet (220 m) below the highest point of the volcano. The whaleback feature measured approximately 1,550 feet (470 m) in length and 500 feet (150 m) in width. The diameter of the new dome was about 1,700 feet (520 m), and it contained about 50 million cubic yards (40 million cubic meters) of material. The total amount of glacier lost by this date was estimated to be 5–10%, but the flow of water from the crater was almost unchanged because the porous nature of the floor of the crater caused the water to be absorbed quickly.
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417:, and surrounding areas. This activity was not considered a large eruption but merely a minor release of pressure consistent with the nature of dome building. Scientists believed it was triggered by a partial collapse of the lava dome. There was no increase in quake activity before the volcanic event.
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Following the collapse of the dome and whaleback, a new feature, termed the "slab", began growing. Approximately the size of a football field, the large, cooled volcanic rock was being forced upward as quickly as 6 feet (1.8 m) per day, though the top part of the slab would usually collapse on a
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followed the steam release, which led seismologists to raise the "alert level" to the third of three levels, indicating a potential threat to life and property. Accordingly, the
Johnston Ridge Observatory overlooking Mount St. Helens was evacuated; television media established their bases at Castle
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or eruption from the lava dome within the next few days. Such an event was expected to be relatively small and not pose a threat to regions beyond the immediate area of the mountain. However, the intensities and occurrences of the earthquakes continued to rise. The largest earthquake recorded was a
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Seismic activity continued to accelerate following the USGS advisory, with earthquakes approaching magnitude 2.5 occurring at a rate of about four per minute on
September 29, prompting the USGS and Pacific Northwest Seismograph Network to issue a second advisory, increasing the "alert level" to the
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After a relatively quiet 2007, on
January 16, 2008, USGS geologist John S. Pallister spotted steam seeping from the lava dome in Mount St. Helens' crater. At approximately the same time, the Pacific Northwest Seismograph Network recorded a magnitude 2.9 earthquake, followed by a small tremor that
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Magma reached the surface of the volcano around
October 11, resulting in the building of a new lava dome on the existing dome's south side. Dome building continued, with the USGS reporting in early November 2004 that magma was being extruded at a rate of 7 to 10 cubic meters per second. Had magma
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By May 5, 2005, the highest point on the new dome was 7,675 feet (2,339 m), 688 feet (210 m) below the highest point of the volcano. It contained approximately 58 million cubic yards (44 million cubic metres) of material. Growth of the new dome continued steadily, and small
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On
February 1, 2005, the new lava dome on Mount Saint Helens measured 7,642 feet (2,329 m) in elevation. This brought its elevation to 1,363 feet (415 m) above the 1980 crater floor, approximately 2,000 feet (610 m) above the surface of the Crater
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lasted for nearly ninety minutes, and a magnitude 2.7 earthquake. But by the end of
January, the lava dome growth had stopped. On July 10, 2008, it was determined that the eruption that began in 2004 had ended, after 5 months of inactivity.
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p.m. PST, when a 36,000-foot (11 km) plume of steam and presumably ash was witnessed emerging from the volcano, accompanied by a tremor that measured about magnitude 2.5. The plume was visible from the metropolitan areas of
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continued to extrude at this rate uninterrupted, the crater would have been completely filled and Mount St. Helens would have regained its former height in about eleven years. The Mount St. Helens
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On
October 6, the U.S. Geological Survey announced that the alert level was being lowered, saying "We no longer think that an eruption is imminent in the sense of minutes or hours."
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about 30 miles (48 km) from the volcano. Between steam releases, elevated seismic activity on the mountain continued with the strongest tremors remaining near magnitude 3.0.
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a.m. PDT and lasted for up to 90 minutes, which may have indicated the movement of magma beneath the mountain. The tremors were followed by a steam release at around 10:40
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earthquakes continued to be observed every few minutes. The whaleback feature disintegrated steadily but continued to be extruded as solidified lava pushed upward from below.
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located at
Johnston Ridge was able to view the new dome especially at night when the glow of new magma was visible via the camera's infrared capabilities.
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Mount St. Helens' eruptive activity continued over the following days, with steam releases occurring on
October 4 at 9:47 a.m., 2:12
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1) earthquakes occurring less than one-half mile (one kilometer) below the 1980s lava dome. Activity increased, and on
September 26, the
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Included in the new dome was a feature dubbed the "Whaleback" (named such because of its close resemblance to the back of a
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about 9,700 feet (about 3 kilometers) into the air (according to pilot reports), from a vent in the then-unnamed
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Lake Viewpoint about nine miles (14 km) away, while tourists moved to various locations for several miles along
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closed the mountain to all climbing. They also closed some trails in the area, due to the risk of
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just southwest of the lava dome. The resulting ash plume was reported to have drifted south to
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and steam to 10,000 feet (3,000 m) above sea level in its October 1, 2004 eruption.
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was built up. The new dome did not rise above the rim of the crater created by the
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Mount St. Helens experienced major activity again on March 8, 2005, at about 5:30
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has been documented as a continuous eruption in the form of gradual extrusion of
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On December 19, 2006, an eruption sent a steam plume billowing over Washington.
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p.m. PDT, which was stronger than the previous steam release. A low-frequency
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October 5: Steam and ash eruption, seen from the Johnston Ridge Observatory.
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547:"Mount St. Helens National Volcanic Monument - Climbing Mount St. Helens"
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On October 3, low-frequency harmonic tremor activity began at around 3:00
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569:"Mount St. Helens Erupts, Spewing Steam, Ash Into Washington State Sky"
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On July 2, 2005, the tip of the whaleback feature broke off, causing a
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p.m. PDT on October 1, 2004, the mountain erupted a plume of steam and
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Time-lapse images of Mount St. Helens dome growth 2004-2008 - by USGS
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Mount St. Helens vented another plume of steam the next day at 12:14
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inside the crater could be observed for the rest of the afternoon.
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second of three levels, and warn of an increased likelihood of a
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478:"Mount St. Helens - Multimedia | U.S. Geological Survey"
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that sent ash and dust several hundred meters into the air.
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p.m.; then again on the morning of October 5 at around 9:03
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On July 21, 2006, the crater rim was reopened to hikers.
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After releasing a cloud of steam on October 2, dust from
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Mount St. Helens National Volcanic Monument's VolcanoCam
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A steam plume rises from the mountain in December 2004
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Mount St. Helens photographs and current conditions
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Mount St. Helens National Volcanic Monument website
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146:2004–2008 volcanic activity of Mount St. Helens
22:2004–2008 volcanic activity of Mount St. Helens
521:Nemiroff, R.; Bonnell, J., eds. (9 May 2006).
16:Volcanic eruption in Washington, United States
176:On September 23, 2004, around 2:00 a.m.
669:2008 natural disasters in the United States
664:2007 natural disasters in the United States
659:2006 natural disasters in the United States
654:2005 natural disasters in the United States
649:2004 natural disasters in the United States
523:"Rock Slab Growing at Mt St Helens Volcano"
500:"New slab growing in Mount St. Helens dome"
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352:'Whaleback' feature on February 22, 2005.
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739:Volcanic eruptions in the United States
644:Natural disasters in Washington (state)
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198:Pacific Northwest Seismograph Network
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33:Mount St. Helens sent a plume of
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506:. May 3, 2006. Archived from
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528:Astronomy Picture of the Day
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202:"notice of volcanic unrest"
95:Skamania County, Washington
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266:Wood Village, Oregon
122:46.19583; -122.18889
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482:vulcan.wr.usgs.gov
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415:Yakima, Washington
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684:Cascade Volcanoes
674:History of Oregon
557:on June 26, 2009.
488:on June 12, 2011.
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504:www.kgw.com
196:(USGS) and
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108:122°11′20″W
638:Categories
464:References
407:Washington
370:lava spine
359:VolcanoCam
229:landslides
150:Washington
105:46°11′45″N
68:Start time
60:2004-10-01
53:Start date
621:from the
607:from the
200:issued a
190:magnitude
162:lava dome
573:Fox News
434:rockfall
244:At 12:02
91:Location
76:End date
625:website
403:Seattle
383:Glacier
216:in the
83:2008-01
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43:Volcano
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334:, and
332:Morton
328:Randle
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97:, U.S.
409:, to
366:whale
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158:magma
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144:The
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