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Volcanoes

Volcanoes. There are 3 types of volcanoes: Shield – VERY large Composite – medium Cinder - small. Vocabulary List – Quiz Chapter 10 Write these out after the power point. caldera cinder cone composite cone crater intraplate volcanism/hot spot. pluton pyroclastic material

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Volcanoes

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  1. Volcanoes There are 3 types of volcanoes: Shield – VERY large Composite – medium Cinder - small

  2. Vocabulary List – Quiz Chapter 10Write these out after the power point • caldera • cinder cone • composite cone • crater • intraplate volcanism/hot spot • pluton • pyroclastic material • shield volcano • viscosity • Volcano • Vent • Sill • Lacolith • Batholith • dike

  3. Differences between volcanoes Origin Content What magma is made of? Silica content – Shield – low silica content- basaltic – “runny” Composite – high silica content – granitic/rhyolitic – viscous (thick) Cinder – high silica content – granitic/rhyolitic – viscous (thick) • Where does magma come from? • Shield – Basaltic magma forms deep down • Composite – andesitic and granitic magma forms from subduction zone • Cinder – granitic and andesitic magma formed at subduction zone.

  4. Differences continued • Gas Content • Gas is held in rock because of high pressure underground (like CO2 in soda). When pressure is reduced the gas tries to escape. • Shield – low gas content because it cools so quickly – volcano therefore doesn’t have the explosive “power”. • Composite – high gas content kept underground therefore has much explosive power since gas escapes all at once. • Cinder – high gas content kept underground therefore has much explosive power since gas escapes all at once.

  5. Explosive Power • Shield – called “quiet” volcano due to its lack of explosiveness ( low silica and gas content) sputters out not viscous • Composite – explosive – very viscous so pressure builds up inside when gas is released the volcano explodes releasing pressure immediately. • Cinder - explosive – very viscous so pressure builds up inside when gas is released the volcano explodes releasing pressure immediately.

  6. Pyroclastic materials • Definition – particles produced in volcanic eruptions • Basaltic lava – viscous rhyolitic magma is charged with gases as the gas expands it blows fragments from the vent.

  7. Factors determining an eruption • Composition – • Temperature of magma – • Dissolved gases -

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