Pseudocolumnar jointing in Paleocene sedimentary rocks (South Unit of Roosevelt National Park, western North Dakota, USA) : 無料・フリー素材/写真
Pseudocolumnar jointing in Paleocene sedimentary rocks (South Unit of Roosevelt National Park, western North Dakota, USA) / 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 | The rocks at ~hip level have odd structures called pseudocolumnar jointing. This is sandstone that has been subjected to intense heating by an ancient lignite coal fire. Subsequent to the fire, cooling of the rocks resulted in slight shrinkage and the formation of contraction cracks. This often happens in lava flows, resulting in true columnar jointing (e.g., Devils Tower in Wyoming, Devils Postpile in California, Giants Causeway in Ireland). In contrast, the pseudocolumnar jointing seen here did not involve volcanism. |
| 撮影日 | 2014-11-25 21:59:16 |
| 撮影者 | James St. John |
| 撮影地 |