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Unformatted text preview: REVIEW LEC 4 ROCK CYCLE The Rock Cycle has 5 interrelated parts 1. MAGMA molten rock that contains mobile ions, suspended crystals and dissolved gasses. Crystallization = the process by which ions arrange into orderly crystalline structures = minerals Mineral grains precipitate from the magma Magma originates : Primarily from upwelling from the mantle along divergent plate boundaries between oceanic plates Also due to subduction of oceanic plates under continental crust so that the old cold plate melts due to increased temperature and pressure as it descends into the asthenosphere. Know the significance of the intersection of the geothermal gradient and the melting point curve (slide 6) Decompression Melting = As mantle rock rises toward the surface there is a decrease in pressure, this causes the rock to form magma (become liquid) Volatiles (water and gasses) in and with the rock as an oceanic plate subducts below a continental plate - decreases the temperature at which the rock melts to form magma. The Sources of heat are: o Friction in the subduction zone o Subduction carries cooler rock to higher temperature at depth o Heat moves up within the mantle via convection cells 2. IGNEOUS ROCK Lec 4 Page 1 There are 2 habitats of crystallization for igneous rocks: Intrusive or Extrusive A. Int rusive rock forms when magma solidifies at depth Pluton a large rock body resulting from intrusion of igneous magma at depth Batholith = a pluton with a surface exposure of >100 km 2 Example: Sierra Nevada batholith in eastern California Dike a tabular, discordant ( vertically oriented) igneous body Sill a tabular, concordant ( horizontally oriented) igneous body B. Extrusive Rock forms when magma comes to the surface as lava or ash and solidifies at the surface....
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This note was uploaded on 09/26/2011 for the course GEOL 3413 taught by Professor Hileman during the Spring '11 term at Oklahoma State.
- Spring '11