Spirit Lake is a

lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...

in Skamania County, Washington, United States, located north of Mount St. Helens. It was a popular tourist destination for many years until Mount St. Helens erupted in 1980. Previously there had been six camps on the shore of Spirit Lake: Boy Scout ( Camp Spirit Lake), the Girl Scout Camp at Spirit Lake, two YMCA camps ( Camp Loowit, and Portland YMCA camp), Harmony Fall Lodge, and another for the general public. There were also several lodges accessible to visitors, including Spirit Lake Lodge and Mt. St. Helens Lodge. The latter was owned and operated by Harry R. Truman, a noted victim of the volcano's 1980 eruption.

Pre-1980 eruption

Prior to 1980, Spirit Lake consisted of two arms that occupied what had been the valleys of the North Fork Toutle River and a tributary. About 4,000 years ago, these valleys were blocked by

lahar A lahar (, from jv, ꦮ꧀ꦭꦲꦂ) is a violent type of mudflow or debris flow composed of a slurry of pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a river valley. Lahars are extr ...

s and

pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...

deposits from Mount St. Helens to form the pre-1980 Spirit Lake. The longest branch of Spirit Lake was about long. A stable outlet channel flowed from the lake to the North Fork Toutle River across a natural dam composed of volcanic material. The level of Spirit Lake remained basically stable, at an altitude of about .Hopson, CA (2008
''Geologic Map of Mount St. Helens, Washington Prior to the 1980 Eruption.''
Scale 1:62,500, Open-File Report no. 2002-468. U.S. Geological Survey, Reston, Virginia.Lipman, PW., and DR Mullineaux, eds. (1981
''The 1980 eruptions of Mount St. Helens, Washington.''
Professional Paper no. 1250. U.S. Geological Survey, Reston, Virginia. 844 pp.

Climate

Pre-eruption weather data from the Spirit Lake Ranger Station indicates the area either had the rare dry-summer variant of the

subarctic climate The subarctic climate (also called subpolar climate, or boreal climate) is a climate with long, cold (often very cold) winters, and short, warm to cool summers. It is found on large landmasses, often away from the moderating effects of an ocean, g ...

(

Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, nota ...

: Dsc), or the rare

cold-summer mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...

(

: Csc), both of which are found only in small areas across the world. Recent climate data for the area is not available to confirm whether the post-eruption site still has either one of these rare climate types.

Mount St. Helens eruption

During the 1980 eruption of Mount St. Helens, Spirit Lake received the full impact of the lateral blast from the volcano. The blast and the debris avalanche associated with this eruption temporarily displaced much of the lake from its bed and forced lake waters as a wave as much as above lake level on the mountain slopes along the north shoreline of the lake. The debris avalanche deposited about of pyrolized trees, other plant material, volcanic ash, and volcanic debris of various origins into Spirit Lake. The deposition of this volcanic material decreased the lake volume by approximately . Lahar and pyroclastic-flow deposits from the eruption blocked its natural pre-eruption outlet to the North Fork Toutle River valley at its outlet, raising the surface elevation of the lake by between and . The surface area of the lake was increased from 1,300 acres to about 2,200 acres and its maximum depth decreased from to . The eruption tore thousands of trees from the surrounding hillsides and swept them into Spirit Lake. These thousands of shattered trees formed a floating

log raft Timber rafting is a method of transporting felled tree trunks by tying them together to make rafts, which are then drifted or pulled downriver, or across a lake or other body of water. It is arguably, after log driving, the second cheapest me ...

on the lake surface that covered about 40% of the lake's surface after the eruption.Lee DB (1993
''Effects of the Eruptions of Mount St. Helens on Physical, Chemical, and Biological Characteristics of Surface Water, Ground Water, and Precipitation in the Western United States.''
Water-Supply Paper no. 2438. U.S. Geological Survey, Reston, Virginia. After the eruption, Spirit Lake contained highly toxic water with volcanic gases seeping up from the lake bed. A month after the eruption, the bacteria-carrying water was devoid of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

. Scientists predicted that the lake would not recover quickly, but the reemergence of phytoplankton starting in 1983 began to restore oxygen levels. Amphibians such as frogs and salamanders recolonized the lake, and fish (reintroduced by fishermen) thrived.Dale, VH, FJ Swanson, and CM Crisafulli, eds. (2005
''Ecological Responses to the 1980 Eruption of Mount St. Helens.''
Springer Science+Business Media, Inc., New York, New York, 342 pp. Larson, D (1993
''The Recovery of Spirit Lake.''American Scientist.
81(2):166-177.

Current water level

The water level of Spirit Lake is maintained at about by draining water through Spirit Lake Outlet Tunnel, a gravity-feed tunnel completed in 1985. The tunnel was cut through Harrys Ridge to South Coldwater Creek, which flows to Coldwater Lake and into the North Fork of the Toutle River. Had the lake level not been stabilized, the dam, which was composed of volcanic avalanche debris created by the 1980 eruption, would have been breached and caused catastrophic flooding within the Toutle River Valley.Swift, CH, and DL Kresch (1983
''Mudflow hazards along the Toutle and Cowlitz Rivers from a hypothetical failure of Spirit Lake blockage. ''
Water-Resources Investigations Report no. 82-4125. U.S. Geological Survey, Reston, Virginia.Kresch, DL (1992
''Development and routing of mudflow resulting from hypothetical failure of Spirit Lake debris dam, Washington.''
Water-Resources Investigations Report no. 91-4028. U.S. Geological Survey, Reston, Virginia.

Gallery

File:St Helens before 1980 eruption.jpg, Spirit Lake prior to 1980 File:MSH80 blast area spirit lake with rainier 10-04-80 med.jpg, Spirit Lake filled with debris from the eruption. October 4, 1980 File:SpiritLake.jpg, Logs covering Spirit Lake, 2009 File:Spirit Lake (Washington).jpg, Spirit Lake File:SpiritLake2012Treemat01.jpg, Tree mats on Spirit Lake, 2012 File:SpiritLake2012Treemat02.JPG, Spirit Lake with tree mats and Mount St. Helens File:MSHtoutleareaedit.jpg, Shows the major changes in hydrology of Mount Saint Helens after its 1980 eruption, including artificial modifications designed to mitigate sediment and water flow. File:View above Mount St. Helens National Volcanic Monument in Washington 2.jpg, View above Spirit Lake

References

External links

* Anonymous, (2006

ttp://volcanoes.usgs.gov/observatories/cvo/ Cascades Volcano Observatory United States Geological Survey, Vancouver, Washington. * Glicken, HX, W Meyer, and MA Sabol, (1989
''Geology and ground-water hydrology of Spirit Lake blockage, Mount St. Helens, Washington, with implications for lake retention.''
Bulletin no. 1789. U.S. Geological Survey, Reston, Virginia. * Evarts, RC, and RP Ashley (1993a

scale 1:24,000, Geologic Quadrangle no. 1679, U.S. Geological Survey, Reston, Virginia. * Evarts, RC, and RP Ashley (1993b

scale 1:24,000, Geologic Quadrangle no. 1681, U.S. Geological Survey, Reston, Virginia. * Patton, V (2007
''Ecological Mysteries of Spirit Lake''
Documentary produced by Oregon Field Guide, Oregon Public Broadcasting. {{authority control Lakes of Washington (state) Lakes of Skamania County, Washington Mount St. Helens Gifford Pinchot National Forest