1. Volcanoes Openings in the Earths Crust That Lets Magma Through and Often Forms a Mountain.

2. Parts of a Volcano Vent: opening through which magma reaches the surface. Crater: Steep depression around the vent. Mountain: made of lava flows or tephra (dust, ash, cinders, bombs) Magma Chamber: area of magma below volcano

3. Where Volcanoes Form Divergent Boundaries Plates spread apart and magma flows to surface Mid-ocean Ridge / East African Rift Convergent Boundaries / Subduction Zone Subduction melts one plate, melted material reaches surface. Mount St. Helens Hot Spots Area of super heated mantle that a plate moves over. Hawaii

4. Hot Spot Video

5. Types of Magma Granitic MagmaAndeseticBasaltic Magma High Silica content Intermediate Low Silica content Thick Intermediate Runny Traps lots of gases Water vapor Intermediate Little trapped gases Pressure builds Intermediate Small pressure build up Explosive Ash eruption Fairly explosive Ash and lava eruption Non-explosive Lava flow eruption

6. Three Types of Volcanoes Shield Volcanoes Cinder Cones Composite Volcanoes

7. Shield Volcano Hot Spots / divergent plate boundaries Basaltic magma: runny, little silica, little trapped gases. Built by layer upon layer of lava flows. Lava oozes and flows. Non-explosive. Broad flat gentle slopes. Usually wider than is tall.

8. Hawaiian Island Shield Volcano

9. Cinder Cone Subduction Zones / Hot spots Granitic magma: Thick, high silica, lots of trapped gases. Built by piles of tephra (dust, ash, cinders, bombs). Explosive. Steep sides and not very tall.

10. Composite Volcano Subduction Zones Has things in common with both cinder cone and shield volcano. Alternating layers of lava flows and tephra. Very tall and dormant for years Cooling lava can seal vent and build pressure. Mount Rainier Andesetic Magma

11. Composite Volcano Video