lecs_20&21_Volcanism

lecs_20&21_Volcanism - IGNEOUS ROCKS •...

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Unformatted text preview: IGNEOUS ROCKS • EXTRUSIVE (Volcanic) – Fine-grained • INTRUSIVE (Plutonic) – Coarse-grained MAGMA • Molten Rock – Usually with dissolved gases • Generated at depth • Eruptions if magma (lava) reaches surface • If doesn’t reach surface, solidifies underground – Intrudes country rock – Intrusive contact – Chill zone – Xenolith VOLCANISM • Lava = magma at Earth’s surface – Usually with dissolved gases – Silica content controls viscosity, explosivity • Pyroclasts – fragments of rock created by explosion • Lava flows – hot, low viscosity liquid • Pyroclastic rocks & lavas = Extrusive rocks – Extrusive rocks commonly form Volcanoes VOLCANISM • Lava = Magma at Earth’s surface – Usually with dissolved gases – Silica content controls viscosity, explosivity • Pyroclasts – fragments of rock created by explosion • Lava flows – hot, low viscosity liquid • Pyroclastic rocks & lavas = Extrusive rocks – Extrusive rocks commonly form Volcanoes VOLCANISM • Lava = Magma at Earth’s surface – Usually with dissolved gases – Silica content controls viscosity, explosivity • Pyroclasts – fragments of rock created by explosion • Lava flows – hot, low viscosity liquid • Pyroclastic rocks & lavas = Extrusive rocks – Extrusive rocks commonly form Volcanoes VOLCANISM...
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lecs_20&21_Volcanism - IGNEOUS ROCKS •...

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