1. Volcano Explosions and Types

2. What causes different types of explosions? Trapped gases: Trapped gases: – Water vapor and carbon dioxide can be trapped in the magma – Results in an explosive eruption Composition Composition – Silica poor – Silica rich

3. Silica Poor Low in silica- basaltic magma Low in silica- basaltic magma – Results in a quiet, non-explosive eruption – Kilauea http://www.youtube.com/watch?v=tcRz_EIZsRk

4. Silica Rich High in silica- granitic High in silica- granitic – Magma being forced upward by denser surrounding rock comes in contact with the crust which is rich in silica – Soufriere Hills http://www.youtube.com/watch?v=8sPyyHY57H4

5. Neither Rich or Poor in Silica Between basaltic and granitic- Andesitic Between basaltic and granitic- Andesitic – Often forms at convergent plate boundaries when one plate slides under the other – Violent eruption – Krakatau http://www.youtube.com/watch?v=JmPuy- pqIQE&feature=related http://www.youtube.com/watch?v=JmPuy- pqIQE&feature=related

6. Forms of Volcanoes Three main types: Three main types: – Shield – Cinder cone – Composite

7. Shield Volcanoes Typically has sloping sides Typically has sloping sides – Caused by basaltic lava spreading out in flat layers Hawaii Hawaii

8. Cinder Cone Steep, loosely packed sides Steep, loosely packed sides – Usually from materials of explosive volcanoes falling back to earth and settling on the mountain sides Paricutin Paricutin

9. Composite Tepha- composed of rock and/or solidified lava Tepha- composed of rock and/or solidified lava Composite volcano is the result of layering Composite volcano is the result of layering – Tephra-lava-tephra-etc. – Often occurs where plates come together and one slides beneath the other Soufriere Hills Soufriere Hills