Intrusive and Extrusive Activity

Intrusive
1. Batholith
  1. large chambers of magma cool underground and form domes of igneous rock
2. Dykes and sills
  1. magma flows into gaps in the surrounding rock, cools and forms vertical dykes and horizontal sills
3. Cooling Cracks
  1. cracks may form as the magma cools
Extrusive
1. Lava Eruptions
  1. Basaltic lava - Constructive
    1. temperature of eruption over 950
    2. flows easily and gas can escape easily. eruptions aren't violent, usually frequently and long periods
  2. Andesitic and Rhyolitic - Destructive
    1. 750-950 degrees eruption. rhyolitic is less than 750
    2. flow less easily and often have blockages. gases can't escape so pressure build and the blockage is cleared by a violent eruption. short lived and intermittent
2. Volcanos
  1. Dome- Destructive. lava is rhyolitic or andesitic. thick lava causes steep sides as it flows shorter distances
  2. Caldera- Destructive. andesitic and rhyolitic. central part collapses as the magma chamber below empties
  3. Shiled- Constructive. Basaltic lava. long linear vent can be several km long
3. Hot Springs
  1. places where groundwater emerges at the surface. if the source is close to an area of recent intrusive activity the water is heated and becomes a hot spring
  2. temperature varies from 20-90 degrees. tourist attractions
4. Geysurs
  1. type of hot spring here hot water and steam are ejected from the surface in a fountain.
  2. groundwater is heated above boiling point by magma in the crust
  3. hot water becomes pressurised and forces its way to the surface
5. Boiling mud pool
  1. another hot spring, form in areas with fine grained soil, water mixes with the soil to make a hot muddy pool

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Intrusive and Extrusive Activity

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