1. Volcanoes Objective: Understanding what causes volcanoes and the different types they form.

2. Volcanoes Volcanic Explosion Volume Determined by The amount of gases trapped in the magma The composition of the magma

3. Volcanoes Granitic Magma = Loud/Explosive Eruption Contains more silica Higher water content More viscous (sticky) Hawaiian Islands Basaltic Magma = Quiet Eruption Contains less silica Less viscous (sticky) Mount St. Helens

4. Volcanoes Andesitic Magma = Explosive Medium silica content Medium viscosity (stickiness)

5. Volcano Types Composite (Stratovolcano) Alternating layers of silica lava and tephra (cinder) eruptions Cinder Cone Tephra (cinder) piles up in steep sided cone Shield Volcano Broad volcano with gently sloping sides; quiet basaltic eruptions

6. Volcano Vocabulary Batholith Largest intrusive rock bodies Form when a large plume of magma cools underground

7. Volcano Vocabulary Dike Magma squeezes into a vertical crack Sill Magma squeezes between horizontal rock layers

8. Volcano Vocabulary batholith laccolith sill dike

9. Volcano Vocabulary Volcanic Neck Weathering and erosion remove the sides of the volcano leaving the solidified vent behind

10. Volcano Vocabulary Caldera When the top of the volcano collapses after a large eruption