Anthodites (Skyline Caverns, Front Royal, Virginia, USA) 20 : 無料・フリー素材/写真
Anthodites (Skyline Caverns, Front Royal, Virginia, USA) 20 / 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 | Anthodites 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. 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.Shown above are anthodites, a scarce variety of speleothem that was first described from this very cave - Skyline Caverns in Virginia. Anthodites are radiating clusters of quill-like to slightly vermiform structures. Individual anthodite quills are hollow. Mineral analysis by White (1994) has shown that they are composed of aragonite (CaCO3), which is a polymorph of calcite. Some have recrystallized to calcite. The anthodites of Skyline Caverns were originally in sealed chambers in a mostly-sediment filled cave passage. During tourist trail construction, workers dug out sediments and encountered small chambers having common anthodites. They were subsequently named and described in the literature in 1949. The anthodite-bearing chambers were unusual in having near-vacuum conditions. Upon opening one chamber, a worker's hat was sucked in by the low air pressure.When pure calcium carbonate, anthodites are white-colored. The yellows and reddish-browns seen above are from iron oxides. The slightly green coloration is from algae that grows in tourist trail lighting.Skyline Caverns is developed in structurally tilted carbonates (mixed dolostones and limestones) of the Rockdale Run Formation (Beekmantown Group, Lower Ordovician).Locality: Skyline Caverns, Front Royal, central Warren County, northern Virginia, USA-------------------Reference cited:White (1994) - The anthodites from Skyline Caverns, Virginia: the type locality. National Speleological Society Bulletin (Journal of Caves and Karst Studies) 56: 23-26. |
| 撮影日 | 2016-05-12 11:32:30 |
| 撮影者 | James St. John |
| タグ | |
| 撮影地 |