EXTRUSIVE IGNEOUSROCKSVolcanoes and Volcanic RocksIgneous Rock Namesand Compositions• IntrusiveRock Name• Peridotite•Gabbro• Diorite•Granite• Compositions• Ultramafic•Mafic• Intermediate• Silicic (felsic)• VolcanicRock Name• (Komatiite)• Basalt•Andesite• RhyoliteMAGMA and LAVA•Magma is the term for any molten silicatematerial, whether below the surface or on top.•Volcanic rocks are erupted on the surface.– Volcanic rocks are fine-grained (<1 mm)•Lava is the term for a magma on the surface.• Low Viscosity• High Temperature (1000 - 1200ºC)• Normally Quiescent Lava Flows–AaAaAaAa - early, low temperature, blocky flow–Pahoehoe - later high temperature ropy flow–Pillow Lavas - underwater flow•Edifice– Shields–Cinder cones• Higher viscosity (higher polymerization)• Lower temperature•Flows– Viscous lava flows– Pyroclastic flows•Edifice– Composite ConesRhyolite Eruptions• Very high viscosity• Low temperature (600 - 800ºC)• Massive Pyroclastic eruptions– Air fall (pumice)– Ash Flow (Nuée Ardente) Tuff•Edifice– Caldera (5 - 25 km)– Resurgent
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