Olivine basalt (Cedar Canyon, Iron County, Utah, USA) 4 : 無料・フリー素材/写真
Olivine basalt (Cedar Canyon, Iron County, Utah, USA) 4 / 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 | Olivine basalt from the Quaternary of Utah, USA.Basalt is a common extrusive igneous rock and is the dominant rock in Earth’s upper oceanic crust. Black lava rocks seen at famous volcanoes such as Mt. Kilauea in Hawaii and Mt. Etna in Sicily are composed of basalt. Basalt has a mafic chemistry. Mafic igneous rocks are generally dark-colored, have 45-52% silica (= SiO2 chemistry) (mafic has also been defined as 45 to 55% silica), are rich in iron (Fe), magnesium (Mg), & calcium (Ca), and are dominated by the minerals plagioclase feldspar and pyroxene. Basalt has an aphanitic texture, which refers to small crystals (all or almost all the crystals are <1 millimeter in size). Aphanitic texture forms by relatively quick cooling of lava. Some basalts are porphyritic or coarsely crystalline if the lava flow took time to cool & solidify (e.g., some Proterozoic basalt lavas in the Keweenaw Peninsula of Michigan's Upper Peninsula).This sample is an olivine basalt. Click on the photo to zoom in - small greenish-colored masses are present. Olivine is not a necessary component of basalt, but it can be present in appreciable amounts.Geologic context: loose piece in the 5 January 2009 Cedar Canyon rockslide site, possibly derived from the Cedar Canyon Basalt (if so, it is lower Middle Pleistocene, 630 ka)Locality: Cedar Canyon Landslide of 5 January 2009, northern side of Route 14 at milepost 8, Cedar Canyon, southeastern Iron County, southwestern Utah, USA--------------------------------See photos & info. at:www.flickr.com/photos/jsjgeology/albums/72157689603306481 |
| 撮影日 | 2019-09-04 16:42:43 |
| 撮影者 | James St. John |
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