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Rhyolite magmas can be produced by igneous differentiation of a more mafic (silica-poor) magma, through fractional crystallization or by assimilation of melted crustal rock . Associations of andesites , dacites , and rhyolites in similar tectonic settings and with similar chemistry suggests that the rhyolite members were formed by ...
Rhyolitic magma is felsic and the most abundant in silica, potassium, and sodium but the lowest in iron, magnesium, and calcium. [1] [3] The silica composition of rhyolitic magma ranges from 65-75 wt.%. [1] It forms in the lowest temperature range, from about 1200 °F to 1470 °F. [1], [3] Rhyolitic magma has the highest viscosity and gas ...
Neither extreme is common in nature, but basalt magmas typically have NBO/T between 0.6 and 0.9, andesitic magmas have NBO/T of 0.3 to 0.5, and rhyolitic magmas have NBO/T of 0.02 to 0.2. Water acts as a network modifier, and dissolved water drastically reduces melt viscosity.
The orange region notes subterranean chambers a type of magma known as basalt -- or, the heat source of eruptions -- is connected to rhyolitic magma, a type of magma that is closer to the surface.
Volcanoes with rhyolitic magma commonly erupt explosively, and rhyolitic lava flows are typically of limited extent and have steep margins because the magma is so viscous. [15] Felsic and intermediate magmas that erupt often do so violently, with explosions driven by the release of dissolved gases—typically water vapour, but also carbon dioxide.
Magma rich in silica and poor in dissolved water is most easily cooled rapidly enough to form volcanic glass. As a result, rhyolite magmas, which are high in silica, can produce tephra composed entirely of volcanic glass and may also form glassy lava flows. [2] Ash-flow tuffs typically consist of countless microscopic shards of volcanic glass. [3]
Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. ... Welded tuff is commonly rhyolitic in composition, but ...
The Bishop Tuff is a high-silicate rhyolitic welded tuff, made up of ash and pumice clasts. The main minerals found in the pumice clasts are biotite, plagioclase, quartz, and sanidine. The main composition is SiO 2 (73.4-77.9%), [3] followed by Al 2 O 3 (12.7%). [7] The Bishop Tuff is compositionally zoned.