Hornfels (Genesse Valley, California, USA) : 無料・フリー素材/写真
Hornfels (Genesse Valley, California, USA) / 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 | Hornfels from California, USA. (public display, Geology Department, Wittenberg University, Springfield, Ohio, USA)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.Hornfels are dense, compact, fine-grained, contact metamorphic rocks. They typically form as the result of contact metamorphism of shales or basalts. Some hornfels have spheroidal to subspheroidal patches of more coarsely-crystalline material - such rocks are called spotted hornfels.Locality: unrecorded/undisclosed site in the Genesse Valley, ~central Plumas County, northern Sierra Nevada Mountains, northern California, USA |
| 撮影日 | 2018-03-24 15:27:11 |
| 撮影者 | James St. John |
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