ERTH 2104 Study Guide - Final Guide: Brain Size, Conchoidal Fracture, Picrite Basalt
3 Nov 2016
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Zoning = plagioclase- core of zoned crystal more calcic than rim. Rhyolite: quartz, feldspar light coloured, small gas bubbles,flow lines or bands volcanic rock, rapid cooling of magma (lots of silica) granite : Deep in earth crust from cooling magma, slow cooling= large crystals. Dark gray to black, weathering turn yellow/brown, fine grained, sometimes contains gas bubbles. Plagioclase feldspars, augite, olivine volcanic rock,rich in iron and mg, poor in silica, erupted and lava cooled quickly. Magma rich in iron and mg poor in silica, forced into cracks of layers of rock near earths surface, cools much slower than basalt= slightly larger crystals. Dark green to black, large grain size. Magma rich in iron, mg, poor in silica. Pumice light in gray to medium grey, large number of gas bubbles surrounded by thin layer of glass, looks like a sponge, light in weight. Explosively blown out of volcanoes, high silica magma.
