Early estimates of the cost of the eruption ranged from US$2–3 billion.^[2] A refined estimate of $1.1 billion ($2.74 billion in 2007 dollars[2]) was determined in a study by the International Trade Commission at the request of the United States Congress.^[2] A supplemental appropriation of $951 million for disaster relief was voted by Congress, of which the largest share went to the Small Business Administration, U.S. Army Corps of Engineers, and the Federal Emergency Management Agency.^[2]

There were also indirect and intangible costs of the eruption. Unemployment in the immediate region of Mount St. Helens rose tenfold in the weeks immediately following the eruption, and then returned to nearly normal once timber salvaging and ash-cleanup operations were underway. Only a small percentage of residents left the region because of lost jobs owing to the eruption.^[2] Several months after May 18, a few residents reported suffering stress and emotional problems, even though they had coped successfully during the crisis. Counties in the region requested funding for mental health programs to assist such people.^{[citation needed]}

Initial public reaction to the May 18 eruption nearly dealt a crippling blow to tourism, an important industry in Washington. Not only was tourism down in the Mount St. Helens–Gifford Pinchot National Forest area, but conventions, meetings, and social gatherings also were canceled or postponed at cities and resorts elsewhere in Washington and neighboring Oregon not affected by the eruption. The adverse effect on tourism and conventioneering, however, proved only temporary. Mount St. Helens, perhaps because of its reawakening, has regained its appeal for tourists. The United States Forest Service and the State of Washington opened visitor centers and provided access for people to view the volcano's devastation.^[2]

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Later eruptions

Further information: 2004 and later volcanic activity of Mount St. Helens

St. Helens produced five more explosive eruptions between May and October 1980. Through early 1990, a total of at least 21 periods of eruptive activity had occurred. The volcano remains active, with smaller, dome-building eruptions continuing into 2008.

An eruption occurred on May 25, 1980 at 2:30 a.m. that sent an ash column 9 miles (14 km) into the atmosphere.^[21] The eruption was preceded by a sudden increase in earthquake activity and occurred during a rain storm. Erratic wind from the storm carried ash from the eruption to the south and west, lightly dusting large parts of western Washington and Oregon. Pyroclastic flows exited the northern breach and covered avalanche debris, lahars, and other pyroclastic flows deposited by the May 18 eruption.^[21]

At 7:05 p.m. on June 12, a plume of ash billowed 2.5 miles (4 km) above the volcano. At 9:09 p.m. a much stronger explosion sent an ash column about 10 miles (16 km) skyward.^[23] This event caused the Portland area, previously spared by wind direction, to be thinly coated with ash in the middle of the annual Rose Festival.^[24] A dacite dome then oozed into existence on the crater floor, growing to a height of 200 feet (60 m) and a width of 1,200 feet (370 m) within a week.^[23]

A series of large explosions on July 22 broke more than a month of relative quiet. The July eruptive episode was preceded by several days of measurable expansion of the summit area, heightened earthquake activity, and changed emission rates of sulfur dioxide and carbon dioxide. The first hit at 5:14 p.m. as an ash column shot 10 miles (16 km) and was followed by a faster blast at 6:25 p.m. that pushed the ash column above its previous maximum height in just 7.5 minutes.^[23] The final explosion started at 7:01 p.m. and continued for over two hours.^[23] When the relatively small amount of ash settled over eastern Washington, the dome built in June was gone.^[25]

Seismic activity and gas emission steadily increased in early August, and on August 7 at 4:26 p.m., an ash cloud slowly expanded 8 miles (13 km) into the sky.^[25] Small pyroclastic flows were sent through the northern breach and weaker outpouring of ash rose from the crater. This continued until 10:32 p.m. when a second large blast sent ash high into the air.^[25] A second dacite dome filled this vent a few days later.

Two months of repose were ended by an eruption lasting from October 16 to October 18. This event obliterated the second dome, sent ash 10 miles (16 km) in the air and created small, red-hot pyroclastic flows.^[25] A third dome began to form within 30 minutes after the final explosion on October 18, and within a few days, it was about 900 feet (270 m) wide and 130 feet (40 m) high. In spite of the dome growth next to it, a new glacier formed rapidly inside the crater.

All of the post-1980 eruptions were quiet dome-building events, beginning with the December 27, 1980, to January 3, 1981, episode. By 1987 the third dome had grown to be more than 3,000 feet (900 m) wide and 800 feet (240 m) high.^[25] At that rate, assuming additional destructive eruptions do not occur, St. Helens' summit would be restored to its previous height sometime in the mid to late 22nd century.

Further eruptions occurred over a few months during 1989–1991, and the mountain became active again in late 2004.

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Summary table

Eruption Summary May 18, 1980 Eruption of Mount St. Helens
Volcano	Elevation of Summit:	Before eruption: 9,677 feet (2,950 m) After eruption: 8,363 feet (2,549 m) Total removed: 1,314 feet (401 m)
	Crater dimensions:	East-West: 1.2 miles (1.9 km) North-South: 1.8 miles (2.9 km) Depth: 2,084 feet (635 m)
	Crater floor elevation:	6,279 feet (1,914 m)
Eruption	Date:	May 18, 1980
	Time of initial blast:	8:32 a.m. Pacific Daylight Time (UTC-7)
	Eruption trigger:	A magnitude 5.1 earthquake about 1 mile (1.6 km) beneath the volcano
Landslide / Debris Avalanche	Area covered:	23 square miles (60 km²)
	Volume: (uncompacted deposits)	0.67 mi³ (2.8 km³)
	Depth of deposit:	Buried North Fork Toutle River to average depth of 150 feet (46 m) with a maximum depth of 600 feet (183 m)
	Velocity:	70 miles per hour (113 km/h) to 150 miles per hour (241 km/h)
Lateral Blast	Area covered:	230 square miles (596 km²); reached 17 miles (27 km) northwest of the crater
	Volume of deposit: (uncompacted deposits)	0.046 mi³ (0.19 km³)
	Depth of deposit:	From about 3 feet (1 m) at volcano to less than 1 inch (2.5 cm) at blast edge
	Velocity:	At least 300 miles per hour (483 km/h)
	Temperature:	As high as 660 °F (349 °C)
	Energy release:	24 megatons thermal energy (7 by blast, rest through release of heat)
	Trees blown down:	4 billion board feet (9.4 million m³) of timber (enough to build about 300,000 two-bedroom homes)
	Human fatalities:	57
Lahars	Velocity:	About 10 miles per hour (16 km/h) to 25 miles per hour (40 km/h) and over 50 miles per hour (80 km/h) on steep flanks of volcano
	Damaged:	27 bridges, nearly 200 homes. Blast and lahars destroyed more than 185 miles (298 km) of highways and roads and 15 miles (24 km) of railways.
	Effects on Cowlitz River:	Reduced carrying capacity at flood stage at Castle Rock from 76,000 ft³/s (2,150 m³/s) to less than 15,000 ft³/s (225 m³/s)
	Effects on Columbia River:	Reduced channel depth from 40 feet (12 m) to 14 feet (4 m); stranded 31 ships in upstream ports
Eruption Column And Cloud	Height:	Reached about 80,000 feet (24,400 m) in less than 15 minutes
	Downwind extent:	Spread across U.S. in 3 days; circled Earth in 15 days
	Volume of ash: (based on uncompacted deposits	0.26 mi³ (1 km³)
	Ash fall area:	Detectable amounts of ash covered 22,000 square miles (57,000 km²)
	Ash fall depth:	10 inches (25 cm) at 10 miles (16 km) downwind (ash and pumice) 1 inch (2.5 cm) at 60 miles (97 km) downwind 0.5 inches (1.3 cm) at 300 miles (482.8 km) downwind
Pyroclastic Flows	Area covered:	6 square miles (16 km²); reached as far as 5 miles (8 km) north of crater
	Volume and depth: (volume based on uncompacted deposits)	0.029 mi³ (0.12 km³); multiple flows 3 feet (1 m) to 30 feet (9 m) thick; cumulative depth of deposits reached 120 feet (37 m) in places
	Velocity:	Estimated at 50 miles per hour (80 km/h) to 80 miles per hour (130 km/h)
	Temperature:	At least 1,300 °F (700 °C)
Other	Wildlife:	The Washington State Department of Game estimated nearly 7,000 big game animals (deer, elk, and bear) perished as well as all birds and most small mammals. Many burrowing rodents, frogs, salamanders, and crawfish, managed to survive because they were below ground level or water surface when the disaster struck.
	Fisheries:	The Washington Department of Fisheries estimated that 12 million Chinook and Coho salmon fingerlings were killed when hatcheries were destroyed. Another estimated 40,000 young salmon were lost when forced to swim through turbine blades of hydroelectric generators as reservoir levels along the Lewis River were kept low to accommodate possible mudflows and flooding.
Brantley and Myers, 1997, Mount St. Helens -- From the 1980 Eruption to 1996: USGS Fact Sheet 070–97, accessed 2007-06-05; and Tilling, Topinka, and Swanson, 1990, Eruption of Mount St. Helens - Past, Present, and Future: USGS General Interest Publication, accessed 2007-06-05.
Table compiled by Lyn Topinka, USGS/CVO, 1997

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See also

• High Cascades
• Geology of the Pacific Northwest
• National Geographic Seconds From Disaster episodes

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Notes

[

References

• Harris, Stephen L. (1988). Fire Mountains of the West: The Cascade and Mono Lake Volcanoes. Missoula: Mountain Press Publishing Company, Missoula. ISBN 0-87842-220-X
• Tilling, Robert I., Topinka, Lyn and Swanson, Donald A. (1990). Eruptions of Mount St. Helens: Past, Present, and Future. The Climactic Eruption of May 18, 1980. U.S. Geological Survey. (adapted public domain text)
• Klimasauskas, Ed (2001-05-01). Mount St. Helens Precursory Activity. United States Geological Survey. Retrieved on 2007-06-05.
• Topinka, Lyn. Mount St. Helens: A General Slide Set, Cascades Volcano Observatory, U.S. Geological Survey. Retrieved on 2007-05-19

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External links

• List of victims
• List of victims with biographical details
• Mount St. Helens — a virtual tour
• USGS: Mount St. Helens 1980 Debris Avalanche Deposit
• USDA Forest Service: Mount St. Helens VolcanoCam
• Pre-1980 Eruptive History of Mount St. Helens, Washington
• Video approximation of the first seconds of the May 18th eruption from Gary Rosenquist's photos

Coordinates: 46°12′01″N, 122°11′12″W

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