Forms of INtrusive activity

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  • Created by: Lilly
  • Created on: 28-02-14 12:14

Dykes

  • Magma flows into gaps in surounding rocks
  • Magma solidifies in vertical fissured (across layers of rock)= form thin vertical veins of igneous rock that form when magma enters and cools
  • Cut across bedding planes of rock into which they have been intruded.
  • Material of dyke usually more resistant- other rocks worn away and dyke is exposed by later erosion.
  • Can be many kilometres in length
  • Form groups- 'Dyke swarm'

Dyke Swarm

  • A major group of parralell/ linear dykes introduced into continental crust
  • Example- Fraser Dyke Swarm
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Sills

  • Horizontal sheet of igneous rock intruded between older rock beds
  • Magma flows into gaps in rock and cools horzontally- between laters of rock.
  • Example- Great Whin Sill, Northumberland
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Batholiths

  • Large chambers of igneous rock- mass of igneous rock, typically diamond shaped, has been intruded between rock strata causing uplift in shape of a dome
  • Form deep below the surface
  • Several hundred Km long
  • Exposed by later erosion
  • Batholiths change the rock that they touch- the heat turns it into a different type of rock= metamorphic auerole
  • Example- Hambledown Tor, Dartmoor
  • Sierra Nevada Batholith USA.
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Lacolith

  • Smaller injections of lava
  • Lense shaped, between layers of rock- very viscous magma, forces overlying rock to DOME
  • Example- Small range of hills 'Eildon Hills' Scottish border
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