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Rhyolite (/ ˈraɪ.əlaɪt / RY-ə-lyte) [1][2][3][4] is the most silica -rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase.
Magmatic water. Magmatic water, also known as juvenile water, is an aqueous phase in equilibrium with minerals that have been dissolved by magma deep within the Earth's crust and is released to the atmosphere during a volcanic eruption. It plays a key role in assessing the crystallization of igneous rocks, particularly silicates, as well as the ...
Spherulite. In petrology, spherulites (/ ˈsfɛrʊlaɪts, sfɪər -/) are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone, and rhyolite as globules about the size of millet seed or rice grain, with a duller luster than the surrounding glassy base of the rock, and ...
Magma (sometimes colloquially but incorrectly referred to as lava) is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural satellites. [3] Besides molten rock, magma may also contain suspended crystals and gas bubbles.
The amount of dissolved gases may be a further factor that controls the eruption event. The deeper the magma chamber is located, the higher is the amount of gas that can be dissolved in the magma (high pressure conditions), especially in andesitic and rhyolitic magmas. As phase separation occurs and the liquid fraction increases along with ...
Volcanic glass is the amorphous (uncrystallized) product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the closely packed, highly ordered array of a crystal and the highly disordered array of liquid. [1] Volcanic glass may refer to the interstitial material, or matrix, in an aphanitic (fine ...
Rhyolitic magmas generally produce finer grained material compared to basaltic magmas, due to the higher viscosity and therefore explosivity. The proportions of fine ash are higher for silicic explosive eruptions, probably because vesicle size in the pre-eruptive magma is smaller than those in mafic magmas. [ 1 ]
If the magma does not contain much gas, rhyolite tends to just form a lava dome, and such eruptions are more common. However, when mixed with gas or steam, rhyolitic eruptions can be extremely violent. The magma froths to form pumice and ash, which is thrown out with great force. Such eruptions tend to be earlier in any given eruption cycle.