Weathered basalt (Quaternary; summit of Inferno Cone, Craters of the Moon Lava Field, Idaho, USA) 5 : 無料・フリー素材/写真
Weathered basalt (Quaternary; summit of Inferno Cone, Craters of the Moon Lava Field, Idaho, 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 |
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| 説明 | Weathered basalt in the Quaternary of Idaho, USA.Southern Idaho’s Snake River Plain represents the track of the Yellowstone Hotspot. Yellowstone is currently located in northwestern Wyoming. In the geologic past, the center of Yellowstone volcanism was in southern Idaho, and before that, it was located in southeastern Oregon. Eight separate, large, dark-colored lava fields cover portions of the modern Snake River Plain: Shoshone Lava Field, Craters of the Moon Lava Field, Wapi Lava Field, Kings Bowl Lava Field, Cerro Grande Lava Field, North Robbers Lava Field, South Robbers Lava Field, and Hell’s Half Acre Lava Field. These lavas erupted during the late Pleistocene and Holocene, well after the Yellowstone Hotspot “migrated” to the northeast. The lavas are so young that little vegetation covers them. Portions of the Snake River Plain's basaltic lava fields have been designated as Craters of the Moon National Monument. The flows & cones in the Craters of the Moon Lava Field range in age from ~15 ka to ~2 ka. The landscape is harshly beautiful and provides an excellent opportunity to closely examine terrestrial basalt volcanism.The photo shows rocks at the summit of a dormant cinder cone volcano in Idaho's Craters of the Moon Lava Field. Cinder cones are relatively small, steep-sided cones of loose igneous debris. They have few eruptions and a relatively large summit crater. Cinder cones are principally composed of scoria and vesicular basalt. Much of Inferno Cone's surface is covered with blackish-colored, scoriaceous mafic glass (= tachylite), which is actually derived from a different, nearby cinder cone. The brown and dark reddish-brown rocks in the picture are weathered/oxidized basalts. Basalt contains minerals having a significant ferromagnesian content. Upon oxidative weathering, the iron component forms various iron oxide minerals, such as hematite and limonite. The resulting colors are dark reddish, rusty red, rusty brown, or orangish brown.Locality: summit of Inferno Cone, Craters of the Moon National Monument, Snake River Plain, southern Idaho, USA |
| 撮影日 | 2011-07-13 12:46:10 |
| 撮影者 | James St. John |
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