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Highest point; Elevation: 6,896 ft (2,102 m) NGVD 29 [1] Coordinates: 1]: Geography; Location: Lassen and Shasta counties, California, U.S.: Parent range: Cascade Range: Topo map: USGS Prospect Peak: Geology; Mountain type: Extinct Cinder cone: Volcanic arc: Cascade Volcanic Arc: Last eruption: 1666: Climbing; Easiest route: Trail hike: Cinder Cone is a cinder cone volcano in Lassen Volcanic ...
Most of the volcanoes in the Oregon Cascades are either scoria cones, small shield volcanoes, or lava fields, though the segment contains a number of basaltic andesite stratovolcanoes such as Mount McLoughlin. [7] Black Butte is one such stratovolcano [4] (also known as a composite volcano), [9] with a mafic (rich in magnesium and iron ...
All of these volcanoes have been extinct for millions of years. [2] The Pilot Knob volcanic complex consists of four small, rounded hills (including Pilot Knob proper) forming the volcano's core area in an area two miles in diameter. The hills are composed of trap rock which is an erosion-resistant, fine-grained mafic volcanic rock.
Belknap was the last volcano to erupt in the Three Sisters area. [21] Basaltic andesite dominates the eruptive material in the local mafic volcanoes, which range from early Pleistocene to Holocene age. [22] Belknap is one of the larger mafic volcanoes in the Sisters Reach, more than 30 of which run continuously along the segment. [22]
The youngest mafic volcano in the Lassen volcanic center, [53] it is surrounded by unvegetated block lava and has concentric craters at its summit. [52] Cinder Cone is comprised by five basaltic andesite and andesite lava flows, and it also has two cinder cone volcanoes, with two scoria cones, the first of which was mostly destroyed by lava ...
A rock with over 90% mafic mineral content will be classified instead as an ultramafic rock. A gabbroic rock with less than 10% mafic mineral content will be classified as an anorthosite. [8] [13] A more detailed classification is based on the relative percentages of plagioclase, pyroxene, hornblende, and olivine. The end members are: [8] [13]
The mafic rocks also typically have a higher density than felsic rocks. The term roughly corresponds to the older basic rock class. [9] Mafic lava, before cooling, has a low viscosity, in comparison with felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava.
Most examples come from areas of active continental rifting such as the Basin and Range Province. Bimodal volcanism has also been described from areas of transtension , [ 2 ] the early phases of back-arc basin formation [ 3 ] and in the products of both continental and oceanic hotspots (e.g. Yellowstone , Anahim and the Canary Islands ).