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  • Created by: Sharon
  • Created on: 18-12-15 10:41
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  • vulcanicity
    • Most explosive
      • convergent boundaries
        • one plate subducted and a release in fluids starts partial melting
      • more silicon dioxide = more viscous = more acidic = explosive.
      • occasional eruptions
      • lava bombs, ash, dust
      • composite dome shaped
    • Least explosive
      • less silicon dioxide = less viscous = basic = little violence
      • mainly lava
      • plateau shield shaped
      • regular and can be monitored
    • pathway
      • magma rise through strata to surface through conduits
      • eruptions at the top due to central vent or side flanks due to diverging conduits
    • FISSURE - elongated crack , tension pulls crust apart laval flows out  (Rifts/early constructive)
    • Extrusive
      • BOILING MUD POOLS -  acidic, limited water, gas to sulphuric acid , = rock into clay, gas escape = bubble.
      • HOT SPRINGS - superheated water in convection current, cools.. no water at eruption temperature.
      • FUMAROLES (steam vents) -  little water all flashes as steam
      • GEYERS - hot springs constrictions in their plumbing. prevent water circulating freely where water would escape. pressure = no boiling. rises = steam, expands water overflows = less pressure and boils, eruption water.
    • Rupture in earth's crust whereby magma gas and fluid reach surface.
    • SHIELD - basaltic rock, gently sloping cones, less viscous, layers of lava (Hotspots)
    • COMPOSITE - most common, layers of ash and lava.  (Destructive)
    • ACID/DOME - steep sides, viscous, cant travel = build up as cone (continental)
    • CALDERAS - blocked gases beneath vent explode = crater, later = small cones (destructive)
    • Classification - eruption
      • magma deep rise as less dense than rock, gas separates (bubbles) grow, high viscous cant expand =pressure = explosive
    • Intrusive
      • PLUTONS -  cooling and hardening of magma. only evident after uplift.
      • SILLS & LACCOLITHS - plutons near the surface. sills magma alongside bedding surface...laccoliths same but viscous pushes rock up.
      • DIKES -  some plutons when magma in fractures cutting across rock layers (cm thick)
      • BATHOLITHS - many individual plutons thick, douzen km into crust.


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