Vulcanicity
- Created by: Labake
- Created on: 02-11-14 17:55
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- Vulcanicity
- Forms of Intrusive Activity
- Dykes
- Forms when magma solidifies in a vertical crack/fissure
- Rock cools and crystallises slowly= large grained rock like granite/dolerite (horizonal cooling cracks)
- Dyke cuts across bedding planes on country rock at a right angle
- E.g. Isle of Skye
- Sills
- Horizontal intrusion along horizontal bedding planes e.g. sedimentary sandstone
- Isle of Skye- Kilt Rock and Whin Sill
- Rock cools and crystallises slowly= large grained rock (granite) with vertical cooling cracks
- Batholiths
- Deep below surface where large masses of magma cool, crystallise and solidify
- Rock cools slowly= course grained igneous rock e.g. granite
- Dome shaped and up to 100's of km diameter
- Largeness, extreme heat and pressure alter surrounding rock
- Called Metamorphism- rock affected called metamorphic aureole e.g. marble
- Largeness, extreme heat and pressure alter surrounding rock
- Can be exposed on surface from erosion e.g. Isle of Arran
- Batholiths feeds dyke/sill an forms smaller dome= laccolith
- Magma moves into lithosphere by exploiting faults
- Magma then cools, crystallises and solidifies= igneous rock
- Forms intrusive features- surounding rock can be worn to expose feature on surface
- Magma then cools, crystallises and solidifies= igneous rock
- Happens at plate margins and above hot spots
- Dykes
- Minor forms of Extrusive Activity
- Geysers
- Explosive plumes of water and steam erupting from the ground
- E.g Great Geyser in Iceland
- Shortlived as groundwater conditions change, vents collapse and new geysers form
- Surface water seeps down through fissures
- Collects as conduits in underground caverns
- Water boils from hot magma intrusions= bubbles
- Bubbles rise with water to surface and expand closer to surface
- Bubbles pop, pressure reduced and massive volumes of steam released quickly= explosion
- Geysers
- Explosive plumes of water and steam erupting from the ground
- E.g Great Geyser in Iceland
- Shortlived as groundwater conditions change, vents collapse and new geysers form
- Surface water seeps down through fissures
- Collects as conduits in underground caverns
- Water boils from hot magma intrusions= bubbles
- Bubbles rise with water to surface and expand closer to surface
- Bubbles pop, pressure reduced and massive volumes of steam released quickly= explosion
- Bubbles pop, pressure reduced and massive volumes of steam released quickly= explosion
- Bubbles rise with water to surface and expand closer to surface
- Water boils from hot magma intrusions= bubbles
- E.g. Yellowstone
- Collects as conduits in underground caverns
- Geysers
- Bubbles pop, pressure reduced and massive volumes of steam released quickly= explosion
- Bubbles rise with water to surface and expand closer to surface
- Water boils from hot magma intrusions= bubbles
- E.g. Yellowstone
- Collects as conduits in underground caverns
- Hot Springs and Boiling Mud
- Hot spring is a release of hot water from underground to the surface- NOT under pressure
- Forms pools (acidic to alkali)- near volcanic areas and near boiling point
- E.g. Blue Lagoon Spa
- Due to minerals dissolving in the water that seeps out of ground
- Hot Springs- groundwater heated from hot rock/magma
- Forms pools (acidic to alkali)- near volcanic areas and near boiling point
- Hot Springs- groundwater heated from hot rock/magma
- Boiling mid pools= hot springs mix with surface sediment in steamy areas
- H2S +O2= H2SO4- dissolves rock into clay and silica- mixes with water
- Hot spring is a release of hot water from underground to the surface- NOT under pressure
- Fumaroles
- Patches of escaping steam from small vents in volcanic areas
- Sometimes with sulphur around edges or a small cone of mineral deposit
- Steam/CO2/H2S- (H2S = solfatara with sulphur deposits
- Steam heated from water seeping in from pecipitation
- Formed when water boils below surface to release steam/ magma degasses with SO2 etc
- Often formed on volcano fissure when main vent is blocked
- Patches of escaping steam from small vents in volcanic areas
- Geysers
- Major forms of Extrusive Activity
- Types of Volcanoes
- See Types of Volcano mindmap
- Types of Volcanoes
- Volcanic activity is the escape of magma from the mantle into the lithosphere (intrusive)/ earth's surface (extrusive)
- Decompression Melting (forming magma)
- Convection currents draw rock into asthenosphere from lower mantle
- Pressure drops allowing the rock to melt
- Happens at constrictive boundaries and Hotspots
- Pressure drops allowing the rock to melt
- Convection currents draw rock into asthenosphere from lower mantle
- Hydration Melting (forming magma)
- In subducting zones where water and other volatiles escape from subducting plate
- Lowers melting temperature of overlying rock in the lithosphere above
- In subducting zones where water and other volatiles escape from subducting plate
- Forms of Intrusive Activity
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