Blue Color of Crater Lake

November 01, 2011

Crater02_26aug11 (2)

: Ray Boren
Summary Author: Ray Boren; Jim Foster
November 2011 Earth Science Picture of the Day Viewer's ChoiceBeginning about 5,000 years ago, water from melting snow, rain and springs began to accumulate in the massive, bowl-shaped caldera of Crater Lake, Oregon. Inflow, seepage and evaporation of this closed drainage system now vary less than 3 ft (1 m) per year. Crater Lake, viewed here from its north rim, is the deepest lake in the U.S., delving 1,943 ft (592 m) at one spot -- average depth is 1,148 ft (350 m). It’s also one of the bluest appearing lakes in the world.

Pure water has an intrinsic pale blue color because it absorbs most of the red wavelengths of light, but its peak transparency is in the blue-green part of the spectrum. When observing light that’s passed through relatively deep water (tens of ft), the colors we detect are the blue wavelengths of light, which aren’t as readily absorbed as the longer wavelength colors. Red light is the first to be absorbed, then orange, yellow and green. Only the deepest blue light gets scattered back to the surface for a lake as deep as Crater Lake. Water color is affected by other considerations as well, including observation angle, reflections from the sky, sediment load, and roughness of the water surface. Photo taken on August 27. 2011.

Photo Details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D60; Focal Length: 18.0mm; Aperture: f/9.0; Exposure Time: 0.0063 s (1/160); ISO equiv: 200; Software: QuickTime 7.6.4.