GEOL 212 Study Guide - Quiz Guide: Orthoclase, Feldspar, Plagioclase
26 Dec 2017
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When melting first occurs, it happens at the peripheries of individual crystal grains (b - right), yielding minute pockets of magma. When these pockets grow to the point that they interconnect (a - right) the magma is able to move. Being liquid, magma tends to be lighter than surrounding material from which it has melted. Thus, it tends to percolate upward by any available means. As this happens, droplets coalesce, eventually forming large magma chambers that can be relatively small (enchanted rock, tx) to very large (sierra nevada batholith). Rocks formed from the solidification of magma are termed igneous. Igneous rocks differ widely depending on: composition: magmas with different chemistries will solidify into different minerals at different temperatures, emplacement process: magma chambers may solidify slowly underground or rapidly upon reaching the surface. Resulting igneous rocks will be radically different in texture, even if their composition is similar.
