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Andesite (/ ˈ æ n d ə z aɪ t /) [1] is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica -poor basalt and silica-rich rhyolite . It is fine-grained ( aphanitic ) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende .
A sample of andesite (dark groundmass) with amygdaloidal vesicles filled with zeolite. Diameter of view is 8 cm. Adakite – Volcanic rock type; Andesite – Type of volcanic rock; Alkali feldspar granite – Type of igneous rock rich in alkali feldspar; Anorthosite – Mafic intrusive igneous rock composed predominantly of plagioclase
The individual crystals in an aphanitic igneous rock are not distinguishable to the naked eye. Examples of aphanitic igneous rock include basalt, andesite, and rhyolite. Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass ...
The Nature Conservancy became concerned about overdevelopment in 1978 and launched its largest fundraising project to that date. Collecting over $500,000 they purchased 1,881 acres (761 ha) of Lower Table Rock, creating the Lower Table Rock Preserve. [32] Projects include prescribed burning and invasive species removal. [37]
Basaltic andesite from Parícutin volcano in Mexico. Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America [1] and the Andes of South America. [2]
Boninite is an extrusive rock high in both magnesium and silica, ... Boninite is considered to be a primitive andesite derived from melting of ... Nature Geosciences ...
Phantom Ship Island is mainly formed from andesite rock that dates from about 400,000 years ago, partly altered by hydrothermal activity. [1] The island is situated on the south east end of Crater Lake and projects more than 200 m (656 ft) out from the wall of the caldera. The island is about 500 ft by 200 ft in size.
The Bearwallow Mountain Andesite is composed of calc-alkaline volcanic rock ranging from basaltic andesite to dacite, but predominantly andesite.These form a group of low cones or shield volcanoes and range in age from 27 to 23 million years old.