Volcanoes Silica (SiO2) and water content controls viscosity of magma



Download 9.1 Kb.
Date conversion03.03.2018
Size9.1 Kb.

Volcanoes

  • Silica (SiO2) and water content controls viscosity of magma.

  • In order of decreasing silica:

  • Rhyolite (most viscous)- lava domes

  • Andesite

  • Basalt (most fluid)- lava flows




Volcanoes




Magma composition

  • Felsic composition – rich in Silica – high viscosity – explosive.

  • Trapped gases (steam 80%, CO2 10%, nitrogen) in magma



Volcano types




  • Shield volcanoes- low angle slopes e.g Hawaii

  • Strato volcanoes- high angle slopes – Mt. St. Helens

  • Caldera – collapsed crater

  • Lava dome – high viscosity dome

  • Cinder cone – small volcano of pyroclastic material (volcanic fragments)




Continental flood basalts

  • India: Deccan Traps: ½ million sq. miles

  • Same age as dinosaur extinction (any connection?)

Pyroclastic material




end


The database is protected by copyright ©ininet.org 2016
send message

    Main page