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Shield Volcanoes

Shield Volcanoes. Basaltic Lava – low silica content, low viscosity, low gas content Hot spots – magma moves up from lower mantle and plates move over it Ex. Hawaii (note: see video on favorites). Shield Volcanoes.

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Shield Volcanoes

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  1. Shield Volcanoes Basaltic Lava – low silica content, low viscosity, low gas content Hot spots – magma moves up from lower mantle and plates move over it Ex. Hawaii (note: see video on favorites)

  2. Shield Volcanoes • Mid Ocean Ridges - volcanoes grow out of mid ocean ridges (constructive margin) • Ex: Iceland – only MOR with an actual volcano Divergent boundary – forming islands from accumulation of basaltic lava

  3. Contd. • Fissures – a crack! The beginning of volcanic activity as magma moves up through the crack towards the surface

  4. Anatomy of a volcano

  5. Shield Volcanoes • Broad shape, gentle slopes - Why??? • Quiet eruptions – Why?? • Lava flows - • Basaltic lava – Why?? • From vents and craters – why?? • 70% of all gases produces from volcanoes is water vapor

  6. Cinder Volcanoes Cinder Cones – smallest volcanoes usually products of a single volcanic eruption lasting only a few weeks (rarely more than 1 year) Forms on continents tall with steep slopes Extremely violent eruptions

  7. Eruptions • Very high silica content • Very little to no lava flow – why?

  8. Eruption characteristics • Once cinder cone volcanoes erupt the pipe that connects the vent to the chamber solidifies and volcano never erupts again • Fragments that come from eruption range from ash to bombs but consists mostly of lapilli (cinders) 2-64 mm in size

  9. Pyroclastic materials • Lapilli – cinders ranging from 2-64 mm in size • Bombs- semimolten material upon ejection and become streamlined after ejection • Blocks – particles that are larger than 64mm in size.

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