vulcanicity
- 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
- convergent boundaries
- 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.
- Most explosive
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