San Francisco Peaks (north of Flagstaff, Arizona, USA) 11 : 無料・フリー素材/写真
San Francisco Peaks (north of Flagstaff, Arizona, USA) 11 / 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 | Arizona's San Francisco Volcanic Field is named after the San Francisco Peaks (San Francisco Mountain), seen here, which are the eroded remnants of an old stratovolcano.The volcanic field consists of more than 600 eruptive centers dating from the Late Miocene to the late Holocene - most are cinder cones. The largest volcano in the field is San Francisco Mountain itself. Activity at San Francisco Mountain Volcano started in the Late Pliocene, at about 2.8 million years ago. Most volcanism here was during the Pleistocene, in the form of andesite lava flows, plus minor dacite and rhyolite. The most recent activity was at ~91,000 years ago.Cinder cones in the field have erupted a variety of igneous products, ranging from mafic to felsic to alkaline in composition - most are alkaline basalt. The most recent activity in the field was in 1064 A.D. at a famous cinder cone called Sunset Crater.The highest peak at San Francisco Mountain currently tops out at 12,633 feet above sea level. Estimates based on reconstructions of the volcano, before eruptive collapse events and subsequent erosion, indicate that the original summit was about 14,600 feet.Locality: San Francisco Peaks, north of Flagstaff, San Francisco Volcanic Field, Coconino County, north-central Arizona, USA |
| 撮影日 | 2007-09-05 14:19:06 |
| 撮影者 | James St. John |
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