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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.
Magma that cools slowly within a magma chamber usually ends up forming bodies of plutonic rocks such as gabbro, diorite and granite, depending upon the composition of the magma. Alternatively, if the magma is erupted it forms volcanic rocks such as basalt , andesite and rhyolite (the extrusive equivalents of gabbro, diorite and granite ...
For example, andesitic magmatism is associated with the formation of island arcs at convergent plate boundaries while basaltic magmatism is found at mid-ocean ridges during sea-floor spreading at divergent plate boundaries. On Earth, magma forms by partial melting of silicate rocks either in the mantle, continental or oceanic crust. Evidence ...
Vulcanian eruptions display several common characteristics. The mass of rock ejected during the eruption is usually between 10 2 and 10 6 tonnes [1] and contains a high proportion of non-juvenile material (> 50%). During active periods of volcanic activity, intervals between explosions vary from less than 1 minute (e.g. Anak Krakatoa) to about ...
Fissure volcanoes pour out low viscosity basaltic magma from fissure vents to form the extrusive rock basalt. [2] Composite or stratovolcanoes often have andesitic magma and typically form the extrusive rock andesite. Andesitic magma is composed of many gases and melted mantle rocks. [2]
A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma into a more evolved, silica rich end member. Rock types of the tholeiitic magma series include tholeiitic basalt, ferro-basalt, tholeiitic basaltic andesite, tholeiitic andesite, dacite and rhyolite.
Magma exists in three main forms that vary in composition. [3] When magma crystallizes within the crust, it forms an extrusive igneous rock. Dependent on the composition of the magma, it may form either rhyolite, andesite, or basalt. [3] Volatiles, particularly water and carbon dioxide, significantly impact the behavior of each form of magma ...
When the magma finally reaches the surface as lava and cools, the rock solidifies around the gas bubbles and traps them inside, preserving them as holes filled with gas called vesicles. [ 2 ] A related texture is amygdaloidal in which the volcanic rock, usually basalt or andesite , has cavities, or vesicles, that are filled with secondary ...