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QAPF diagram with basalt/andesite field highlighted in yellow. Andesite is distinguished from basalt by SiO 2 > 52%. Andesite is field O2 in the TAS classification.. Andesite is an aphanitic (fine-grained) to porphyritic (coarse-grained) igneous rock that is intermediate in its content of silica and low in alkali metals.
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.
The andesite line is the most significant regional geologic distinction in the Pacific Ocean basin. It separates the mafic basaltic volcanic rocks of the Central Pacific Basin from the partially submerged continental areas of more felsic andesitic volcanic rock on its margins.
Image credits: historians Historian Liz Covart explains that history isn't just about what happened but how we interpret it as well. "The past happened, but history is made," Liz says. "Every ...
Dacite from the Lassen Volcano National Park. Dacite (/ ˈ d eɪ s aɪ t /) is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides.
The pyroclastic material making up a cinder cone is usually basaltic to andesitic in composition. [6] It is often glassy and contains numerous gas bubbles "frozen" into place as magma exploded into the air and then cooled quickly. Lava fragments larger than 64 mm across, known as volcanic bombs, are also a common product of cinder cone ...
Phreatomagmatic ash is formed by the same mechanisms across a wide range of compositions, basic and acidic. Blocky and equant clasts with low vesicle content are formed. [2] ...
Somewhat later, andesitic lavas poured out from what is now Reading Peak and mainly flowed to the south and east, reaching the head of Warner Valley. By this time, the park's eastern portion had been transformed into a relatively flat plain. [1] The activity was followed by an eruption of the Eastern basalts from volcanoes east of the park. [11]