Glacial striations on lava (Lassen Volcano National Park, California, USA) 3 : 無料・フリー素材/写真
Glacial striations on lava (Lassen Volcano National Park, California, USA) 3 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
|---|---|
| 説明 | Pleistocene-aged glacial striations developed on lava in California, USA.Glaciers are rivers of ice. Ice is a mineral (H2O). Glacial ice is a rock (technically, a metamorphic rock). Despite being solid, ice does flow under certain conditions at the Earth’s surface. Occasionally, Earth experiences Ice Ages, during which extensive ice sheets cover and move over significant portions of the Earth’s surface. As ice moves over landmasses, it erodes underlying rocks and picks up small to large pieces of debris. This debris accumulates at the base of the ice sheet and scrapes bedrock as the glacier moves, resulting in glacial scratches (glacial striations) (= thin scratch lines on rock) and glacial grooves (= large channels incised in rock).Locality: Bumpass Hell Trailhead, south of Mt. Lassen, Lassen Volcano National Park, northeastern California, USA |
| 撮影日 | 2010-07-14 14:13:56 |
| 撮影者 | James St. John |
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