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Volcanoes and Plate Tectonics

Volcanoes and Plate Tectonics. Volcano: a weak spot in the crust where molten material or magma comes to the surface Magma: a molten mixture of rock-forming substances, gases, and water from the mantle Lava: what magma is called when it reaches the surface. Volcanoes at Plate Boundaries.

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Volcanoes and Plate Tectonics

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  1. Volcanoes and Plate Tectonics Volcano:a weak spot in the crust where molten material or magma comes to the surface Magma:a molten mixture of rock-forming substances, gases, and water from the mantle Lava:what magma is called when it reaches the surface

  2. Volcanoes at Plate Boundaries • 600 active volcanoes on land • Volcanic belts form along the plate boundaries • One famous volcanic belt is the RING OF FIRE

  3. Volcanoes occur at: • Divergent boundaries • Convergent boundaries Island arc: string of islands created by erupting volcanoes Hot spot: area where material from deep within the mantle rises and then melts • Volcanoes form above hot spots

  4. Mapping Earthquakes and Volcanoes • Google Earth and Catastrophic Events World map • Latitude & Longitude locations given

  5. Properties of Magma Element: a substance that cannot be broken down into other substances - examples: Carbon (C), Hydrogen (H), Oxygen (O) Compound: a substance made of two or more elements that have been chemically combined – examples: water (H2O), carbon dioxide (CO2)

  6. Physical property: any characteristic of a substance that can be observed or measured without changing the composition of the substance. Examples: density, hardness, melting point, smell, freezing point Chemical property: any property that produces a change in the composition of matter. - ability to combine or react with other substances Examples: when burned: changes color, produces a gas, forms new substance

  7. Properties of Magma Viscosity: the resistance of a liquid to flow • High viscosity = slow moving = thick magma • Low viscosity = fast moving = thin magma • The viscosity of magma depends upon its silica content and temperature Silica: compound made of oxygen and silicon • Silica content of magma = 50-70% • more silica = higher viscosity, forms rhyolite rock (similar to granite) • less silica = lower viscosity, forms basalt rock

  8. Types of lava Pahoehoe: fast moving, hot lava that has a low viscosity • Looks like a whole bunch of wrinkles Aa: slow moving, high viscosity lava • Looks like large lava chunks puffed up • Which type am I?

  9. Parts of a Volcano Magma chamber: located underneath the volcano where the magma collects Pipe: a long tube in the ground that connects the magma chamber to the earth’s surface Vent: the opening in the volcano where molten gas and rock are expelled Lava flow: area covered by lava as it pours out of the vent Crater: bowl-shaped area that forms on top of the volcano located around the central vent *Tell students volcano diagram page #, quiz to follow on Tuesday

  10. http://egsc.usgs.gov/isb/pubs/teachers-packets/volcanoes/poster/poster.htmlhttp://egsc.usgs.gov/isb/pubs/teachers-packets/volcanoes/poster/poster.html • http://www.brainpop.com/science/earthsystem/volcanoes/

  11. Types of Eruptions Quiet Eruption: eruption where magma is low in silica and has a low viscosity • Lava flows quietly from the vent and can flow for many kilometers Shhhhh… the volcano is erupting!

  12. Explosive Eruption: eruption where magma has a high silica content and viscosity • Magma can flow out of the crater or build up in the volcano’s pipe until it explodes (think of cork getting stuck in a bottle) • Produces bombs and cinders Pyroclasic flow: mixture of hot gases, ash, cinders, and bombs

  13. Life Cycle of a Volcano • Active: volcano that is erupting or has shown signs that it may erupt in the near future • Dormant:volcano that is expected to awaken in the future and become active • Extinct: volcano considered to be dead and is unlikely to erupt again Aerial view of volcano

  14. Volcanic Landforms Shield Volcanoes: quiet eruptions that gradually build up a gently sloping mountain Cinder Cone Volcanoes: explosive eruptions that creates a cone-shaped hill from ashes, cinders and bombs building up around the vent Composite Volcanoes: cone shaped mountains formed from layers of lava and ash from quiet and explosive eruptions

  15. Lava Plateaus: made up of many layers of thin runny lava that erupt from long cracks in the ground Calderas: massive hole left by the collapse of a volcano. • Read page 102 to see how they form

  16. Landforms from Magma Volcanic Necks: forms when magma hardens in a volcanoes neck – looks like a giant tooth Batholiths: rock formed when a large body of magma cools inside the crust • Read pages 103 - 104

  17. Geothermal Activity Hot Springs: forms when groundwater is heated by a nearby body of magma or by hot rock deep underground Geyers: fountain water and steam that erupts from the ground Geothermal Energy: using water heated by magma to provide energy (pipes, turbine  generator)

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