Frictionite (Early Miocene, 21-22 Ma; Sandy Creek, NNW of Panguitch, Utah, USA) 7 : 無料・フリー素材/写真
Frictionite (Early Miocene, 21-22 Ma; Sandy Creek, NNW of Panguitch, Utah, USA) 7 / 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 | Frictionite from the Miocene of Utah, USA. (~2.1 centimeters across at its widest)Frictionite is a rare rock. It has a glassy to finely-frothy texture and forms by friction-induced melting of rocks along the base of an active landslide. In this black-colored example from Utah, the resulting material resembles volcanic glass.Felsic volcanic glass (usually black) is called "obsidian". Black-colored, mafic volcanic glass is called "tachylite". Golden-brown colored, mafic volcanic glass is called "sideromelane". Because this frictionite resembles volcanic glass, it is also known as "pseudotachylite". Pseudotachylites can form by frictional heating along deep fault zones (fault pseudotachylites) or from impact events (impact pseudotachylites). This landslide pseudotachylite is the rarest variety.See:www.flickr.com/photos/jsjgeology/albums/72157646983567557andwww.flickr.com/photos/jsjgeology/albums/72157645693093630Because pseudotachylite can form by different specific processes (faulting, impact, landslides), one should always specify which type.The frictionite seen here is from the basal surface of the Markagunt Megalandslide, the largest landslide deposit in Utah. Mapping by the Utah Geological Survey has shown that the Markagunt Megalandslide deposit extends 2000 or more square miles. The landslide itself consists of Tertiary-aged volcanic rocks (lahar deposits, lava flows, volcanic tuffs) and volcaniclastic rocks. The detachment area was the Tushar Mountains area of southern Utah. The landslide deposit is almost 65 miles long and reaches 40 miles across in places. Movement occurred during the Early Miocene, at 21 to 22 million years ago.The sample is from a frictionite-filled fissure just below the landslide deposit.Locality: outcrop along Sandy Creek, about 9.3 kilometers north-northwest of Panguitch, southern Utah, USA-----------------------------Video at:www.flickr.com/photos/136031402@N06/53903015029-----------------------------Info. at:geology.utah.gov/map-pub/survey-notes/update-markagunt-gr... |
| 撮影日 | 2025-03-03 12:39:07 |
| 撮影者 | James St. John |
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