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Volcanoes

Volcanoes. volcanism : any activity that includes the movement of magma toward the surface of the Earth volcano : place where magma reaches the surface. magma : liquid, molten rock underground lava : magma that reaches the surface lost gas, gained rock. Major Volcanic Zones.

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Volcanoes

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  1. Volcanoes

  2. volcanism:any activity that includes the movement of magma toward the surface of the Earth volcano: place where magma reaches the surface

  3. magma: liquid, molten rock underground • lava: magma that reaches the surface • lost gas, gained rock

  4. Major Volcanic Zones • MID-OCEAN RIDGE: occurs where plates are moving apart • lava flows out smoothly and fluidly from cracks

  5. SUBDUCTION ZONE: occurs at subduction boundaries • usually explosive and erupted material is mostly lava

  6. HOT SPOTS: areas of volcanic activity in the middle of a lithospheric plates

  7. Hawaiian Islands are an example

  8. two types of lava: • felsic: much silica (Rhyolitic), light-colored, slow moving (viscous), continental crust

  9. mafic: low silica (basaltic), dark-colored, fast moving (least viscous), oceanic crust

  10. Pahoehoe (puh-HOEEE-hoeee): thin mafic lava. • usually hardens with wrinkled surface • means “ropey” in Hawaiian Pahoehoe Lava

  11. Aa Lava • Aa (AH-ah): sharp block shapes of hardened mafic lava. • caused by rapid cooling on surface of lava • breaks into jagged chunks

  12. Aa Lava Pahoehoe Lava

  13. Pahoehoe

  14. Aa

  15. Pillow lava from Hawaii

  16. many magmas contain dissolved gases that are given off • water vapor, carbon dioxide (CO2), sulfur (S) • magmas with more gases have more explosive eruptions

  17. tephra:solid fragments ejected from a volcano ash (<2mm) bombs lapilli (<64mm) blocks Sometimes called pyroclastic material

  18. lapilli

  19. bombs

  20. bombs

  21. blocks

  22. Vent: opening from which lava flows • Crater: funnel-shaped pit or depression at top of volcano • Caldera:craters whose walls have collapsed

  23. Shield Volcano • composed of quiet lava flows • form gently sloping, dome- shaped mountain • basaltic (mafic) magma

  24. largest = Mauna Loa in Hawaii

  25. Cinder Cone Volcano • Made mostly of tephra and other rock particles • Formed from explosive eruptions • Not very high, narrow base, steep sides • Rhyolitic (felsic) magma

  26. Composite Volcano • built up of alternating layers of rock & lava • explosive eruptions at first with tephra, then quiet with lava • forms large, cone-shaped mountains • made of rhyolitic & basaltic magma

  27. Mount Fuji

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