Big Hole (volcano)
| Big hole | ||
|---|---|---|
 East edge of the Big Hole, Oregon |
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| height | 1447.8 m (varies) | |
| location | United States ( Lane County , Oregon ) | |
| Mountains | Cascade Range (Cascade Range) | |
| Coordinates | 43 ° 25 '31 " N , 121 ° 18' 44" W | |
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| Type | Maar | |
| Last eruption | 20,000 years ago | |
Big Hole is a large maar crater in Fort Rock Basin , Lake County , Oregon near Oregon Route 31 , northeast of Crater Lake . It has a diameter of 1,820 m and is 91 m deep. Big Hole is close to the smaller but better preserved maar crater Hole-in-the-Ground .
description
The crater is surrounded by a 24 to 30 m thick ring of tuff . The Tuffablagerungen extend 1.8 to 2.5 km above the crater rim out and are - possibly due to the prevailing wind direction at the outbreak - on the northeast side of the powerful , where the Big Hole Butte form. The tuffs are deposited in 5 to 100 cm thick layers , show in places a winding layer created by landslides ( convolute bedding , see photo above) and consist of lapilli tuff and tuff breccias that contain sideromelan , a hyaloclastic volcanic glass . Are often volcanic bombs of basalt, which can reach up to 2.5 m in diameter. The proportion of non-volcanic host rock is low.
Terrain steps in the crater indicate that clods of rock collapsed into a cavity formed during the phreatomagmatic explosion , which could explain the size of the maar. Similar processes have also led to the formation of the large Eifel maars, for example in the case of the Meerfelder Maar or the Dreiser Weiher .
environment
Big Hole is part of the volcanic Cascade Range (Cascade Range), which extends from northern California to southern British Columbia extends. The subsurface of the cascade chain consists of fragments of the earth's crust that have been added to the west coast of North America ( accretion ) by the subduction of the Juan de Fuca plate since the Paleogene . For about five million years, the volcanic activity caused by the melting of the subducted earth's crust has been particularly brisk. Due to the composition of the rising magma ( andesite and dacite ), which is influenced by the crust material, volcanism is often explosive.
Individual evidence
- ↑ Some Aspects of the Eruption Mechanism of the Big Hole Maar, Central Oregon . January 14, 1970. Retrieved September 19, 2008.
- ^ Gerhard H. Eisbacher: North America . In: Geology of the Earth . 1st edition. tape 2 . Ferdinand Enke Verlag, Stuttgart 1986, ISBN 3-432-96901-5 , p. 143 .
Web links
- CVO Menu - Fort Rock and Vicinity, Oregon . USGS / Cascades Volcano Observatory. March 6, 2002. Retrieved April 29, 2008.
- GH Heiken, RV Fisher and NV Peterson: A Field Trip to the Maar Volcanoes of the Fort Rock - Christmas Lake Valley Basin, Oregon . In: United States Geological Survey (Ed.): Geological Survey Circular . No. 838, 1981. Retrieved April 29, 2008.