GEOL 306 Lecture Notes - Lecture 6: Rhyolite, Basalt, Viscosity
9 Feb 2020
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Document Summary
Know that basalt is low-silica, that andesite and dacite are intermediate-silica, and that rhyolite is high-silica. Silica atoms in magma actually form tetrahedra with oxygen atoms. The higher the silica content of a magma, the more opportunity for tetrahedra to bump into each other and potentially form these links. Magma evolve-more likely to erupt (higher silia, higher viscosity magma, higher gas content magma) Crystallization fractional crystallization is the removal of early formed crystals from an originally homogeneous magma (for example, by gravity settling) so that these crystals are prevented from further reaction with the residual melt. Melting or incorporating the surrounding wall rock. Injections of new magma into a static magma chamber, mixing two magma types. Stoping: blocks of country rock, falling into magma. Continental crust: high silica 75% (granitic & rhyolitic) Subductions zones contain more gas than others. Sierra nevada batholith-erosions makes mountains such as el capitan & half. The falloonlith plate subducted under north american plate.
