Spirit Lake (Washington)

Spirit Lake is a lake 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.

Human history
The body of water was named "Spirit" by settlers after histories from Native American people in the area spoke of haunting spirits at the lake. The spirits, telling a story of life and death, formed out of the mists into various shapes of trees and animals, foretelling impending doom but good fortune in the afterlife. Any person who saw the apparitions were dead within a week.

A post office named Spirit Lake existed for a brief time, renamed to "Lange" in 1910 after the postmaster. Early mining around the lake began at the turn of the 20th century and necessitated the first road to the area in 1901, replacing a treacherous trail considered unfit for wagons.

Geoglogic history
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 mi 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 3198 ft.

1980 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 850 ft above lake level on the mountain slopes along the north shoreline of the lake. The debris avalanche deposited about 430000000 m3 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 56000000 m3. 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 and 206 ft. 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 to 110 ft. 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.

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. 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.

Water levels
The water level of Spirit Lake is maintained at about 3406 ft by draining water through Spirit Lake Outlet Tunnel, a gravity-feed tunnel completed in 1985. The 8465 ft 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.

An attempt to upgrades and repair the 1985 tunnel began in 2021 but was halted due to concerns over damages to the pumice plain. The project restarted in 2024 and a temporary road, following the prior access path to the lake, will be rebuilt with future work to involve the installation of gates to the tunnel and dredging to prevent the buildup of logs. During the efforts planned through 2027, several trails surrounding the area will no longer be accessible during weekdays.

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 (Köppen climate classification: Dsc), or the rare cold-summer mediterranean climate (Köppen climate classification: 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.