Lecture 12 Notes 9.28 - GS1004 Spotila 28 September 2016 Lecture 12 Consequences of Tectonics The Rock Cycle II volcanoes Relevant reading Chp 5 p

Lecture 12 Notes 9.28 - GS1004 Spotila 28 September 2016...

This preview shows page 1 - 2 out of 6 pages.

GS1004 Spotila 28 September 2016 Lecture 12: Consequences of Tectonics: The Rock Cycle II - volcanoes Relevant reading: Chp. 5, p. 136-167. Motivating questions: What controls style of eruption in volcanoes? What controls hazards of volcanoes? Volcanic eruption: extrusive magma erupts from fissures or conduits, flowing downhill or erupting into the air and settling back down into layers. The style of volcanic eruption depends on viscosity (resistance to flow) of the magma. Low viscosity = runny, easily flows High viscosity = stiff, resists flow; explosive What controls magma viscosity? Viscosity is mainly controlled by presence of silica tetrahedra. (Also temperature, gas content.) Felsic = more viscous (has a lot of silica) Mafic = less viscous Mafic magma (basalt); not explosive, flows easily. Shield volcano = mafic, low viscosity lava, flows downhill; minimal explosions, gently sloping layers and sides of the volcano; form at hotspots and mid-ocean ridges (rift zones) Are shield volcanoes dangerous?
Image of page 1

Want to read all 6 pages?

Image of page 2

Want to read all 6 pages?

You've reached the end of your free preview.

Want to read all 6 pages?

  • Spring '08
  • AKSinha
  • Volcano, volcanic eruption, Shield Volcanoes, LOOK-UP ITEMS, low viscosity lava

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture