Spirit Lake (Washington)
| Spirit Lake | |
|---|---|
(February 2005)
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| Location | Mount St. Helens National Volcanic Monument, Skamania County, Washington, US |
| Coordinates | 46°16′23″N 122°08′06″W / 46.27306°N 122.13500°WCoordinates: 46°16′23″N 122°08′06″W / 46.27306°N 122.13500°W |
| Primary inflows | Precipitation, streams |
| Primary outflows | Drainage tunnel |
| Basin countries | United States |
| Surface elevation | 3,406 feet (1,038 m) (3,198 ft (975 m) before May 18, 1980) |
Spirit Lake is a lake north of Mount St. Helens in Washington State. The lake was a popular tourist destination for many years until the 1980 eruption of Mount St. Helens. Prior to 1980, there were six camps on the shore of Spirit Lake: a Boy Scout camp (Columbia Pacific Council), a Girl Scout camp, two YMCA camps (Longview YMCA camp Loowit, and Portland YMCA camp), Harmony Fall Lodge, and another for the general public. There were also a number of lodges catering to visitors, including Spirit Lake Lodge and Mt. St. Helens Lodge; the latter was inhabited by Harry R. Truman, who became one of the volcano's victims.
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 lahars and pyroclastic flow deposits from Mount St. Helens to form the pre-1980 Spirit Lake. The longest branch of Spirit Lake was about 2.1 miles (3.4 km) 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 3,198 ft (970 m).
Pre-eruption weather data from the Spirit Lake Ranger Station indicates the area had the rare dry-summer variant of the subarctic climate (Köppen type Dsc), found in 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 this rare climate type.
During the 1980 eruption of Mount St. Helens, Spirit Lake received the full impact of the lateral blast from it. 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 850 ft (260 m) above lake level on the mountain slopes along the north shoreline of the lake. The debris avalanche deposited about 350,000 acre-feet 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 46,000 acre-feet. 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 197 ft (60 m) and 206 ft (63 m). The surface area of the lake was increased from 1,300 acres to about 2,200 acres and its maximum depth decreased from 190 ft (58 m) to 110 ft (34 m). 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 on the lake surface that covered about 40% of the lake’s surface after the eruption.
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