064-ANT0132
| Object name | Dry Valleys: Patterned Ground around Commonwealth Glacier |
| 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 will grow and deform the surface over time. Viewed from above, these wedges form circular, polygonal, rectangular, stepped and striped patterns. This photo was shot from a helicopter hovering around 1,000 feet. The next photo shows the cracks up close. |
| Copyright notice | © Irma Hale |