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  • Extrusive, volcanismIntrusivePlutonic activity
  • Volcanoes

    1. 1. VolcanoesKatelyn Kilgore
    2. 2. What volcanoes are…• An opening in the planet’s crust• Causes volcanic ashes and gases to escape• Found where plates are diverging or converging
    3. 3. Vulcanism • Magma is expelled onto the surface (still molten) • Magma solidifies on the surface • Magma solidifies far below the surface
    4. 4. Volcanism• Lava- magma that has departed and has contacted with the surface• Rock fragments• Solidified lava blobs• Ashes• Dust• Gas• steam
    5. 5. Distribution • About 550 active volcanoes • Surface and underwater eruptions • Associated with plate boundaries
    6. 6. Factors of an eruption• Surface crust strength• Pressure• Chemicals – Silica (SiO2) is believed to be the main source of very explosive eruptions – Low silica content usually produces more of a fluid explosion
    7. 7. Classifications • Broad • Sloping gently • Layers of lava flow • “quiet” eruptions • Examples: Hawaiian Islands and Tahiti
    8. 8. Classifications• Large and steep• Lava flows, pyroclastics, hardened mud flow deposits• Both “quiet” and explosive eruptions• Examples: Mt. Fuji, Mt. Rainier, Mt. Shasta, Mt. Vesuvius, Mt. St. Helens
    9. 9. Classifications • Small and sometimes an irregular shape • Plug of lava that is covered by pyroclastics (frequently occurs in the crater of Composite Volcano) • Examples: Lassen Peak, Mono Craters
    10. 10. Classifications• Small and steep sided• May be composed of ash or cinder-sized pieces• Produces “quiet” and explosive eruptions• Examples: Paricutin, Sunset Crater
    11. 11. Other Classifications • Caldera- produced when volcano explodes and/or collapses • Volcanic Neck- small, sharp spire that rises abruptly above the surrounding land
    12. 12. Hazards• Lava Flows – Rarely cause loss of life – Does damage to the area around it – Either moves fast or slow – Flow on predictable paths
    13. 13. Hazards • Eruption Column and Clouds – Consists of pyroclastic material and gases – Volcanic ash and dust form a cloud – Volcanic bombs – Can damage crops and collapse buildings
    14. 14. Hazards• Pyroclastic Flows – Avalanche of hot gases, ash, and rock fragments – Also called nuée ardente – Burns and buries anything in its path
    15. 15. Hazards • Volcanic Mudflows – Caused by heavy rain or melting of snow and glaciers – Water combined with ash and pyroclastic flow – Fast-moving slurry of mud and boulders – Buries the valley floor – Also known as Lahars
    16. 16. Can it be prevented?• Unfortunately no, because it is a natural occurrence all we can do is be prepared for when a volcano blows its top.
    17. 17. Works CitedFisher, Richard V. "The Volcano Information Center." Volcano Information Center (VIC). Web. 07 Dec. 2011. <http://volcanology.geol.ucsb.edu/>.McKnight, Tom L., and Darrel Hess. "Chapter 14 The Internal Processes.“ Physical Geography: a Landscape Appreciation. Eighth ed. Upper Saddle River, NJ: Prentice Hall, 2005. Print.Topinka, Lyn. "CVO Menu - Volcanic Hazards, Features, and Phenomena.“ USGS Cascades Volcano Observatory (CVO). 30 Jan. 2003. Web. 07 Dec. 2011. <http://vulcan.wr.usgs.gov/Glossary/framework.html>."Volcano - Credo Reference Topic." Credo Reference Home. Web. 07 Dec. 2011. <http://www.credoreference.com/topic/volcano>."Volcano | Define Volcano at Dictionary.com." Dictionary.com | Find the Meanings and Definitions of Words at Dictionary.com. Web. 07 Dec. 2011. <http://dictionary.reference.com/browse/volcano>."Volcano." Wikipedia, the Free Encyclopedia. Web. 07 Dec. 2011. <http://en.wikipedia.org/wiki/Volcano>.