Patterned Ground in Katmai National Park, Alaska
August 12, 2011
Photographer: Bill Burton
Summary Author: Bill Burton
The photo above showing a classic example of patterned ground was taken in Katmai National Park and Preserve, Alaska. This location is not far from the vent of the great June 6-9, 1912 ash eruption that resulted in the Valley of Ten Thousand Smokes. Patterned ground has been produced locally by repeated freezing and thawing of the thick, wet, pumice surface that blankets this area. The polygonal shapes are each about five inches (a dozen or so cm) across and accentuated by dark brown cryptobiotic soil -- a combination of cyanobacteria and lichen. Cryptobiotic soil may be the most abundant life form in this part of the park, nearly a century after the eruption. For some reason this soil prefers the substrate at the edges of the polygons, which, due to size sorting during the freezing and thawing, is typically coarser-grained than that found in the polygonal centers, Photo taken on June 14, 2011.
Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot G6; Focal Length: 7.2mm; Aperture: f/4.0; Exposure Time: 0.0063 s (1/160); ISO equiv: 800; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB.