Travertine knobstone (coralloids; "cave popcorn") (Shenandoah Caverns, Quicksburg, Virginia, USA) 7 : 無料・フリー素材/写真
Travertine knobstone (coralloids; "cave popcorn") (Shenandoah Caverns, Quicksburg, Virginia, USA) 7 / James St. John
| ライセンス | クリエイティブ・コモンズ 表示 2.1 |
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| 説明 | Travertine knobstone in a cave in Virginia, USA."Cave formations" in caves are technically called speleothem. Most speleothem is composed of travertine, a crystalline-textured chemical sedimentary rock composed of calcite (CaCO3). Travertine forms in most caves and at some springs by precipitation of crystals from water. Pure travertine is white. The colors seen in the travertine shown above are from iron oxides. Travertine speleothem occurs in a wide variety of forms. The most common variety of travertine speleothem is dripstone, which forms by the action of dripping water. The second-most common type of travertine speleothem is flowstone, which forms by precipitation of crystals from relatively thin films of flowing water. Flowstone typically has the appearance of a frozen waterfalls.The pustulose to nodulose travertine speleothem shown above is knobstone (a.k.a. "cave popcorn"; a.k.a. coralloids). There are multiple proposed origins of knobstone, including:1) water seeping through cave bedrock and through cave popcorn itself2) thin films of water flowing over wall irregularities3) splash from dripping water4) water moving by capillary action from pools into walls5) condensation water6) aerosolsShenandoah Caverns is developed in structurally tilted carbonates of the Conococheague Formation (Upper Cambrian). The tilted bedding is quite evident in this photo.Locality: Shenandoah Caverns, Quicksburg, southern Shenandoah County, northern Virginia, USA |
| 撮影日 | 2016-05-13 10:40:52 |
| 撮影者 | James St. John |
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