ERS120H5 Lecture Notes - Lecture 1: Asthenosphere, Convergent Boundary, Oceanic Crust
Document Summary
Two main information we need, to name the igneous rock. Silicic (felsic) rich in silica, looking at silicate minerals. If the rock is rich in silica, can be called silicic or felsic. Temperature decreases from (more iron and magnesium) to (more silica and oxygen) Happens because different minerals melt at different times. Discontinuous, it stops precipitating sooner or later. Last things to crystalize are the ones with high silicate. If crystals are big = intrusive rock, cooled slowly. Extrusive = cools fast, small crystals: volcanic, volcanic ash and la(cid:448)a flo(cid:449)s don"t ha(cid:448)e insulation. Intrusive = cools slowly, large crystals: plutonic, batholith and sills = insulation from earth. Iron/magnesium rocks have higher density, felsic/silicic rocks have low density. Olivine would be high density because it has high concentration of magnesium. To correctly name an igneous rock, we need to utilize composition and texture, not color, color could be definitive but not always.
