- VolcanoMount Bachelor (formerly known as Bachelor Butte) in central Oregaon is a symmetrical stratovolcano, which is part of a 25 km long volcanic chain SE of South Sister. The chain is aligned N-S and consists of the main volcano of Mt Bachelor itself, cinder cones, small shield volcanoes, and lava flows. The youngest eruption (dated by comparison with known dates of overlying and underlying layers) occurred about 6000 years ago at the Egan scoria cone on the north flank. It produced a lava flow that overlies (=is younger than) ash from the 6850 year BP eruption of Crater Lake.
Volcano type stratovolcano normal or dormant Location United States Summit elevation 2763 m / 9,065 ft Bachelor volcano eruptions 5800 BC ± 1000 (tephrochronology) Typical eruption style ExplosiveThe young basaltic-andesite and basaltic Mount Bachelor volcanic chain was formed in 4 eruptive phases dating back to only about 18,000-15,000 years ago.
The NNW-SSE chain of cinder cones south of Mount Bachelor had been built by about 12,000 years before present. Mount Bachelor itself is one of the youngest edificies on the chain.