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Chapter 18 - Volcanoes

Chapter 18 - Volcanoes. 18.1 Volcanism. Volcanism. Describes all processes associated with the discharge of magma, hot fluids, and gases.

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Chapter 18 - Volcanoes

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  1. Chapter 18 - Volcanoes 18.1 Volcanism

  2. Volcanism • Describes all processes associated with the discharge of magma, hot fluids, and gases http://images.google.com/imgres?imgurl=http://www.kidsgeo.com/images/volcanicim.jpg&imgrefurl=http://www.kidsgeo.com/geology-for-kids/0049-volcanism.php&h=200&w=300&sz=10&hl=en&start=5&tbnid=2qhJLJRLrxKp3M:&tbnh=77&tbnw=116&prev=/images%3Fq%3Dvolcanism%26gbv%3D2%26hl%3Den

  3. Magma • Slushy mixture of molten rock, mineral crystals, and gases • Lava = magma that reaches the surface http://www.stmarys.ca/conted/webcourses/GEO/GEO99/pubigneous/liquidlava.jpg

  4. Volcanoes • Distribution of volcanoes is not random • Most from at Plate Boundaries • Majority are at convergent and divergent boundaries

  5. Convergent Volcanism • Occur at subduction zones • Oceanic plate descends into mantle • Magma moves upward • Mixes with rocks, minerals, and sediment • Form explosive volcanoes

  6. Subduction Zone

  7. Two Major Belts of Convergent Volcanoes • Circum-Pacific Belt • Mediterranean Belt http://survivoralert.com/images/platesAndVolcanoes.gif

  8. Divergent Volcanism • Occurs where plates are moving away from each other • New floor forms as magma rises • Non-explosive, Large amounts of lava • Mostly underwater volcanoes

  9. Hot Spots • Unusually hot regions of mantle where high-temperature plumes of magma rise to the surface • Ex: Hawaiian islands • Rate of plate movement can be calculated from position of volcanoes

  10. Hot Spot Formation • Hot spot remained stationary but Pacific plate slowly moved northwest • Left trail of islands

  11. Flood Basalts • Non-viscous lava that flows through surface of Earth out of cracks called fissures http://www.fas.org/irp/imint/docs/rst/Sect17/lipmap2.gif

  12. Notes 18.1 B Continue “Volcanoes”

  13. Anatomy of Volcano • Conduit = tubelike structures through which lava flows • Vent = opening where lava reaches surfae • Lava cools and solidifies • Over time it accumulates to form a volcano

  14. Anatomy of Volcano • Crater = bowl-shaped depression at top of volcano • Calderas = large depressions formed when magma chamber is emptied http://www.cpluhna.nau.edu/images/wupatk1.jpg

  15. Caldera http://volcanoes.usgs.gov/Imgs/Jpg/Aniakchak/dds40-039_large.jpg

  16. Types of Volcanoes • Shield • Cinder cone • Composite/Stratovolcano

  17. Shield Volcanoes • Broad, gently sloping sides • Circular base • Formed as layers of lava accumulate from non-explosive eruptions

  18. Shield Volcano http://vulcan.wr.usgs.gov/Imgs/Jpg/Hawaii/Images/MaunaLoa79_mauna_loa_shield_volcano_05-79_med.jpg http://www.dkimages.com/discover/previews/793/5103249.JPG

  19. Mauna Loa, Hawaii Shield Volcano

  20. Cinder Cone Volcanoes • Steep slopes, generally small • Form as small pieces of magma are ejected into the air • Pieces = tephra – pile around vent

  21. Cinder Cone http://192.107.108.56/portfolios/m/muscara_j/toolsvis/images/colorcindercone2.jpg http://images.google.com/imgres?imgurl=http://www.cotf.edu/ete/images/modules/volcanoes/typesa.GIF&imgrefurl=http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html&h=236&w=265&sz=13&hl=en&start=4&tbnid=1cbnv3DoRKQHNM:&tbnh=100&tbnw=112&prev=/images%3Fq%3Dcinder%2Bcone%2Bvolcano%26gbv%3D2%26hl%3Den

  22. Composite Volcanoes • Cone-shaped with concave sides, much bigger than Cinder Cone • Formed of layers of hardened chucks from violent erupts alternative with layers of lava oozing down slope

  23. Composite Volcanoes http://www1.moe.edu.sg/learn@/Quest/winners/primary/yu_neng_pri_volcano_nc/versuvius.htm http://www1.moe.edu.sg/learn@/Quest/winners/primary/yu_neng_pri_volcano_nc/xplopix9.gif

  24. Mount Vesuvius http://www.assessrisk.com/italy2006/d9_14.jpg

  25. In-Class Assignment • Volcano Cube

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