Three Sisters (Oregon)
From Wikipedia, the free encyclopedia
| South Sister | |
|---|---|
 South Sister from the southeast |
|
| Elevation | 10,363 feet (3,158 metres) |
| Location | Oregon, USA |
| Range | Cascade Volcanic Arc, Cascade Range |
| Prominence | 5,598 ft (1,706 m) |
| Coordinates | |
| Topo map | USGS South Sister 44121-A7 |
| Type | Complex volcano/Shield volcano cluster |
| Age of rock | Quaternary |
| Last eruption | 1600 years ago |
| Easiest route | hike |
The Three Sisters are three volcanic peaks of the Cascade Volcanic Belt and the Cascade Range, located about 15 miles SW from the nearest town of Sisters, Oregon. They are in the Three Sisters Wilderness Area.
The North Sister is oldest, with towering rock pinnacles and glaciers. It has not erupted since the late Pleistocene. It is the most dangerous climb of the Three Sisters, due to its level of erosion, and thus rockfall.
The Middle Sister is the smallest and most poorly studied. It is also the middle in age. No reports on its potential for eruptions have been made.
The South Sister is the youngest and tallest volcano of the trio. It is a complex volcano which last erupted about 1600 years ago. It has a well developed crater, which holds a glaciated lake. It is a long, steep, non-technical hike that can be easily completed in a day by reasonably fit hikers. Popular starting points are the Green Lakes or Devil's Lake trailheads.
[edit] Recent history
The Sisters were named Faith, Hope, and Charity by early settlers.
In 2000, a satellite discovered that there was a deforming uplift 3 miles south of the South Sister. This could mean that the mountain is awakening. It is also possible that magma involved with the deformation could stop moving towards the surface and cool underground and it is possible that it may be some time before any eruptive activity were to occur. The type of magma involved in the uplift, the amount present and its properties would determine the nature of any eruptive activity. Activity could range from quiet emission of lava flows to more explosive and destructive eruptions. In mid-2005, it seems unlikely that any severe or catastrophic eruption would occur if an eruption were to occur in the near future. An eruption might or might not be centered at the current summit crater. A new vent or vents could open at or near the location of the uplift, and might produce lava flows, new cinder cones or other small volcanoes, or both. Activity could occur in more than one location around the volcano. At about 10 AM PST on Tuesday, 23rd March 2004, an earthquake swarm began with epicenters in the area of uplift. The hundreds of small earthquakes subsided over several days. USGS scientists had been expecting such earthquake swarms to accompany the uplift, and they are not considered precursory events to an eruption.
In September of 2005, scientists discovered a rising bulge about three miles southwest of the South Sister. The ground in a 100 square-mile area is rising at a rate of 1.4 inches per year. Scientists believe that a lake of fluid (likely magma), 1 mile across and 65 feet deep has formed at a depth of 4.5 miles below the unpopulated area. The pooling fluid could be shifting magma or the creation of a new volcano.
[edit] External links
- Bulge on South Sister Slows Down -- Oregonlive.com
- Forest Service information
- Maps and aerial photos
- WikiSatellite view at WikiMapia
- Topographic map from TopoZone
- Aerial image from TerraServer-USA
- Surrounding area map from Google Maps
- Location in the United States from the Census Bureau
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| BC: Mount Silverthrone | Mount Meager | Mount Cayley | Mount Garibaldi WA: Mount Baker | Glacier Peak | Mount Rainier | Mount St. Helens | Mount Adams OR: Mount Hood | Mount Jefferson | Three Sisters | Broken Top | Mount Bachelor | Newberry Volcano | Mount Thielsen | Mount Mazama | Mount McLoughlin CA: Medicine Lake Volcano | Mount Shasta | Lassen Peak |
