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. With the eruption and resulting megatsunami, thousands of trees were torn from the surrounding hillside after lake water was displaced 800 feet up the hillside. Lahar and pyroclastic flow deposits from the eruption then blocked the North Fork Toutle River valley at its outlet, raising the surface elevation of the lake by over 200 ft (60 m). The newly raised lake, once it reappeared, was also 10 percent smaller and much shallower. 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. The water level of Spirit Lake is maintained at about 3,406 feet (1,038 meters) by draining water through a gravity-feed tunnel completed in 1985.