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Object name Dry Valleys: Patterned Ground
Caption In areas of perennially frozen ground, permafrost patterns often form in the loose sand and gravel. Called ice polygons, or patterned ground, they can have diameters of between 30 and 100 feet. The polygons in the Dry Valleys are defined by cracks that open slightly and fill with sand when the frozen ground cools. These cracks can be several feet wide. When the polygons warm, the sand in the cracks prevents them from squeezing shut again, creating a pressurized ice mixed with sand. The cracks willgrow and deform the surface over time. Viewed from above, these wedges form circular, polygonal, rectangular, stepped and striped patterns. This photo shows the cracks up close. The previous photo was shot from a helicopter hovering around 1,000 feet.
Copyright notice © Irma Hale