Porphyritic phonolite (Eocene, 49 Ma; Devils Tower, northeastern Wyoming, USA) 2 : 無料・フリー素材/写真
Porphyritic phonolite (Eocene, 49 Ma; Devils Tower, northeastern Wyoming, USA) 2 / 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 principal scenery at America's first national monument in northeastern Wyoming is a distinctive igneous feature called Devils Tower. It has been variously interpreted as a volcanic neck (probable), an eroded laccolith (unlikely), or an eroded stock (possible). The vertical to subvertical striations along the sides of Devils Tower represent columnar jointing, formed as the original molten rock cooled and contracted. Devils Tower is one of three classic localities on Earth that have excellent columnar jointing - the other sites are Devils Postpile in California and Giants Causeway in Ireland. The rocks of Devils Tower are 49 million year old porphyritic phonolites, formed during the Eocene.Locality: Tower Trail, Devils Tower National Monument, northeastern Wyoming, USA |
| 撮影日 | 2010-08-15 15:04:12 |
| 撮影者 | James St. John |
| 撮影地 |