Minor Extrusive Landforms

Refers to Plate Techtonics and Assosiated Hazrads (AQA A2 Geography)

Detailed info on minor extrusive landforms. The text book and revision guide don't go into much detail on this. There is potential it might come up as an 8-marker, so might be work a look.

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  • Minor Extrusive Landforms
    • Geysers
      • Charactaristics
        • Hot water can shoot up to 60m in the air
        • Hot spring that erupts for short periods of time and periodic intervals.
      • Formation
        • Water is geysers is believed to boil through contact with hot underground rocks or volcanic gases
          • Pressure builds up until an eruption takes place.
            • The vent then refills with water, hence repeating the cycle periodically.
        • Short-lived features in geological terms as ground water conditions can change, causing vents to collapse.
      • Case Study (Old Faithful Geyser, Yellowstone National Park)
        • Near Wyoming, Yellowstone National Park, USA.
        • Each eruption occurs every 45 - 125 minutes, shooting 14,000 - 32,000 litres of water between 32-56 m in the air. Each eruption lasts 2 - 5 minutes.
    • Hot Springs and Boiling Mud
      • Characteristics
        • Natural springs which produce hot water, usually above core human body temperature.
        • Neither hot springs or boiling mud pools are not under pressure so don't explode like geysers.
      • Formation
        • Hot Springs occur when groundwater is constantly heated (but not boiled) by rocks under the surface.)
        • Boiling mud pools form where steam and gas rises to the surface under rainwater pools. Acid attacks the surface rocks, forming clay.
      • Case Study (Rotorura, North Island, New Zealand)
        • Mud pools are just one of the many landforms of geothermal activity that occur here.
        • The largest mud pool is known as 'Hell's Gate'
    • Fumaroles / Solfratara
      • characteristics
        • Fumaroles are more widespread but not as spectacular as a geyser, letting out low pressure outlets of steam.
        • Solfratara are similar to fumaroles, but with a distinctive yellow colour.
      • Fomation
        • Low pressure outlets associated with active and dormant volcanoes (often thousands of years after a volcano becomes extinct.)
        • Gases from fumaroles are mainly steam and carbon dioxide, but also carbon monoxide and hydrochloric acid.
        • If gas is sulphurous (hence yellow) than fumaroles are called Solfratara.
      • Case Study (Solfratara, Bay of Naples, Italy)
        • Shallow Volcanic Crater near Naples in Italy
        • Dormant Volcano which still emits steam and sulphurous gases, giving it it's distinct yellow colour.
        • The crater floor has many mud pools and fumaroles.


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