Muscovite schist (Appalachian Gap, Green Mountains, Vermont, USA) 5 : 無料・フリー素材/写真
Muscovite schist (Appalachian Gap, Green Mountains, Vermont, USA) 5 / 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 | Metamorphic rocks result from intense alteration of any previously existing rocks by heat and/or pressure and/or chemical change. This can happen as a result of regional metamorphism (large-scale tectonic events, such as continental collision or subduction), burial metamorphism (super-deep burial), contact metamorphism (by the heat & chemicals from nearby magma or lava), hydrothermal metamorphism (by superheated groundwater), shear metamorphism (in or near a fault zone), or shock metamorphism (by an impact event). Other categories include thermal metamorphism, kinetic metamorphism, and nuclear metamorphism. Many metamorphic rocks have a foliated texture, but some are crystalline or glassy.Schist is an intermediate- to high-grade, foliated metamorphic rock. It is highly variable in appearance, depending on the mineral content, which is a function of the precursor rock and specific temperature-pressure conditions. Garden-variety schists form by metamorphism of phyllites. Schists typically have medium- to large-sized crystals, unlike the microcrystalline nature of slate & phyllite.Schist's foliated texture (= crystals aligned into bands or stripes or layers) is often only seen when specimens are viewed on edge.The outcrop seen here is muscovite-rich schist in Vermont's Green Mountains. The area's geology is complex - not sure what the formation name is, or the age.Locality: outcrop at Appalachian Gap overlook along Route 17, west of Irasville, Green Mountains, north-central Vermont, USA |
| 撮影日 | 2006-09-09 12:28:11 |
| 撮影者 | James St. John |
| タグ | |
| 撮影地 |