Broken Top This rugged mountain is Broken Top, found in Oregon’s Three Sisters Wilderness. The

Broken TopThis rugged mountain is Broken Top, found in Oregon’s Three Sisters Wilderness. The peak is an extinct volcano, part of the Cascade Range that produced the nearby Three Sisters volcanoes.The volcano started growing on this site at least 150,000 years ago, possibly earlier (it is often difficult to date rocks buried at the bottom of a volcano due to erosion and later eruptions). It grew first as piles of basaltic eruptions, and then evolved to more felsic compositions as its height increased. Large, explosive eruptions at this site sent debris as far away as northern California.The volcano has been quiet for at least the last 10,000 years, possibly longer – more than enough time for glaciers to scour and shape the slope. The irregular, multi-peak shape of the edifice reflects the combination of waning eruptions on this site and glacial erosion. As the peak is several hundred meters shorter than the nearby Three Sisters, it is now a popular hiking and climbing destination.-JBBImage credit:https://commons.wikimedia.org/wiki/File:Broken_Top_Oregon_volcano.jpgReferences:http://on.doi.gov/2gvobrOhttp://bit.ly/2fPIGLghttps://pubs.er.usgs.gov/publication/ofr99437 -- source link

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