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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

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 volcanoes1
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

contd
Contd.
  • Fissures – a crack! The beginning of volcanic activity as magma moves up through the crack towards the surface
shield volcanoes2
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
cinder volcanoes

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

eruptions
Eruptions
  • Very high silica content
  • Very little to no lava flow – why?
eruption characteristics
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
pyroclastic materials
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.