Crater Lake is the Oregon crater lake famous for its deep blue water and lack of rivers flowing in or out.
The lake occupies part of the caldera formed when Mount Mazama collapsed after a major volcanic eruption about 7,700 years ago. Rain and snowfall now fill the basin, while evaporation and underground seepage remove water. Because no streams enter or leave it, the lake’s water balance depends directly on precipitation and the surrounding rock.
Its intense blue colour comes from exceptional clarity and depth: water absorbs longer red, orange, and yellow wavelengths, allowing blue light to dominate. At about 1,949 feet (594 metres), Crater Lake is the deepest lake in the United States. Wizard Island, a cinder cone rising from the water, is one of its most recognizable features.
The lake forms the centrepiece of Crater Lake National Park, established in 1902 as Oregon’s only national park. A frequent misconception is that “no rivers” means no water movement at all; groundwater seepage still occurs, and the lake is continually renewed by snow and rain.