Three Sisters (Oregon)

Three sisters
Three Sisters , view from the southeast
height	3159  m
location	Oregon , USA
Mountains	Cascade chain
Notch height	1706 m
Coordinates	44 ° 6 ′ 13 ″  N , 121 ° 46 ′ 9 ″  W Coordinates: 44 ° 6 ′ 13 ″  N , 121 ° 46 ′ 9 ″  W
Type	Group of shield and stratovolcanoes
Age of the rock	quaternary
Last eruption	about 2000 years ago
First ascent	1898 by Thomas Gerdine

The Three Sisters (Engl. Three Sisters ) are three volcanic peaks in the central part of the Cascade Range in the State of Oregon , USA .

They rise in the Three Sisters Wilderness Area , a 979 km² wilderness area that lies within the Willamette and Deschutes National Forests . The three peaks are named for the surrounding 809 km² Three Sisters biosphere reserve .

Surname

The name Three Sisters first appeared on Preston's Map of Oregon in 1856. As early as the early 1840s, according to the records of a Methodist Church mission in Salem , the three peaks from north to south are Faith (Faith), Hope (Hope) and Charity .

The three volcanoes got their common name because they are so close together and work as a unit. The nearby Mount Bachelor ( bachelor ) got its name from this apparition; he rises at a certain distance from the Three Sisters and makes a comparatively lonely impression.

Geology and volcanic activity

North Sister

The North Sister (3,074 m) is the oldest of the three volcanoes with towering rock needles and glaciers . The last eruption of the shield volcano took place in the late Pleistocene , which is why it is considered extinct. The North Sister has more dykes than any comparable peak in the Cascade Range. The rock was pushed aside by today's summit cone. Part of the cone are the two highest points of the volcano called Prouty Peak and South Horn . Climbing the mountain is more dangerous than the other two of the Three Sisters due to the falling rocks. The notch height is 831 m.

Middle Sister

The Middle Sister (3,062 m) is the smallest and least explored mountain among the Three Sisters. The summit area was originally conical, but the east side in particular was deformed by glaciers . The stratovolcano consists mainly of basalt , but also has andesite , dacite and rhyodacite . The Middle Sister is considered extinct, because the last eruption took place around 50,000 years ago. The volcano is younger than the North Sister and slightly older than the South Sister. Due to its location between the other two, the Middle Sister has the lowest notch height at 344 m.

South Sister

The South Sister (3,159 m) is the youngest and highest volcano of all. The volcanic rocks are basaltic andesite , rhyolite and rhyodacite. It last erupted about 2000 years ago. In its crater lies the permanently frozen Teardrop Pool, the highest lake in Oregon. There are two comparatively small glaciers near the summit, named after Lewis and Clark . A day's hike is sufficient for hikers to climb the mountain. Popular starting points are the Green Lakes and Devil's Lake . The notch height is 1706 m.

Satellite images were taken in 2001 that show changes in the earth's surface in the form of uplifts five kilometers south of the South Sister Summit. The deformations indicate a possible awakening of the volcano in the near future. However, it can also be assumed that magma cools down before it emerges from the surface due to increased contact with solid rock and is thus slowed down. Further observations showed that when the activity increases, it is less the main crater than other parts of the mountain that erupt.

gallery

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  North Sister at sunrise

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  Middle Sister from the northwest

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  South Sister from the air

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  The Three Sisters in December 2008

Web links

Commons : Three Sisters  - collection of images, videos and audio files

• Information about the Three Sisters Wilderness Area
• Summitpost.org via North Sister
• Summitpost.org via Middle Sister
• Summitpost.org via South Sister
• Photos and information, especially about South Sister

Individual evidence

1. ^ ^{A b} South Sister in the Global Volcanism Program of the Smithsonian Institution (English). Retrieved December 16, 2010
2. ^ Willamette National Forest , United States Forest Service , accessed December 16, 2010
3. ^ Biosphere Reserve Information: United States, Three Sisters. Retrieved December 29, 2012 . 
4. ^ Lewis A. McArthur (1974): Oregon Geographic Names (4th edition), Oregon Historical Society, Portland, Oregon, p. 544, ISBN 0875951023
5. ↑ ^{a b c d e f} Stephen L. Harris (2005): "Chapter 13: The Three Sisters". Fire Mountains of the West: The Cascade and Mono Lake Volcanoes (3rd edition), Mountain Press, Missoula, Montana, ISBN 0-87842-511-X
6. ↑ ^{a b c d} Description: Three Sisters Volcanoes, Oregon , United States Geological Survey , accessed December 16, 2010
7. ↑ David R. Sherrod, Edward M. Taylor, Mark L. Ferns, William E. Scott, Richard M. Conrey, and Gary A. Smith (2004), Geologic Map of the Bend 30- × 60-Minute Quadrangle, Central Oregon (PDF; 678 kB), Geologic Investigations Series I – 2683, US National Geodetic Survey, accessed December 16, 2010
8. ↑ North Sister, Oregon , Peakbagger.com, accessed December 16, 2010
9. ↑ Middle Sister Volcano , United States Forest Service , accessed December 16, 2010
10. ↑ Middle Sister, Oregon , Peakbagger.com, accessed December 16, 2010
11. ^ South Sister Data Sheet , National Geodetic Survey , accessed December 16, 2010
12. ^ South Sister, Oregon , Peakbagger.com, accessed December 16, 2010
13. ^ New Evidence Indicates Continuing Uplift at Three Sisters, Oregon , Cascades Volcano Observatory, USGS , accessed December 16, 2010
14. ↑ Information Statement , USGS, accessed December 16, 2010