Search results
Results From The WOW.Com Content Network
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 ...
A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include basalt, diabase and gabbro. Mafic rocks often also contain calcium-rich varieties of plagioclase ...
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]
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 calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic magma, which is high in magnesium and iron and produces basalt or gabbro, as it fractionally crystallizes to become a felsic magma, which is low in ...
Rhomb porphyry is an example with large rhomb shaped phenocrysts embedded in a very fine grained matrix. [4] Volcanic rocks often have a vesicular texture caused by voids left by volatiles trapped in the molten lava. Pumice is a highly vesicular rock produced in explosive volcanic eruptions. [citation needed]
Trachyte (/ ˈ t r eɪ k aɪ t, ˈ t r æ k-/) is an extrusive igneous rock composed mostly of alkali feldspar.It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, [1] and is formed by the rapid cooling of lava (or shallow intrusions) enriched with silica and alkali metals.