L07_18_Sept_Petrology

the co2 comes from the atmosphere so chemical

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Unformatted text preview: does not subduct into the mantle because it is too buoyant (it is less dense than the mantle) early Earth later Earth primiAve rocks evolved rocks dense (‘heavy’) less dense (‘light’) (chemical weathering, long- term carbon cycle) high CO2 consumpAon high Note: these are general pa[erns that are not necessarily true in every situaAon low CO2 consumpAon (rate of chemical weathering) low (phys & chem weathering produces) ferAle soils ocean crust “ultra- mafic” “mafic” rocks rocks less ferAle soils conAnental crust “felsic” rocks The three basic rock types: Igneous All rock material starts out as igneous rock, that is, rock that solidifies directly from the liquid phase (magma, lava). Extrusive igneous rocks form by cooling of magma that reaches the Earth’s surface (lava). Typically fine- grained (small crystals). Intrusive igneous rocks form by cooling of magma within the earth. Typically coarse- grained (large crystals). Sedimentary Comprised of weathered fragments (ground- up bits)...
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This document was uploaded on 03/26/2014 for the course GEC AS.270.103 at Johns Hopkins.

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