1. Volcanoes

2. Anatomy of a Volcano Conduit (pipe) in center Vent on top Crater = steep-walled depression

3. Magma Some magmas have dissolved gasses in them Gasses rise & cause pressure –Like a soda bottle

4. Viscosity –A substance’s resistance to flow Determined by –Composition – type of rock (more silica = higher viscosity) Basaltic Lava = not viscous Andesitic Lava = very viscous –Temperature – cooler temperatures = higher viscosity –The more viscous the more explosive the eruption

5. Eruptions The most viscous (cold, silica) gassy lavas have the greatest eruptions

6. Types of Volcanos 1. 1.Shield Volcanoes Are broad, slightly domed structures Produced by fluid basaltic lavas Some form islands in ocean (ex. hawaii & iceland)

7. 2.Cinder Cones Eject lava fragments the size of cinders into the air High in gas-rich basaltic magma small, usually only erupt once (maybe a few times)

8. 3. 3.Composite Cones gas rich magma with andesitic composition (lots of silica) – causes very viscous lavas have explosive eruption The Ring of Fire Found in the Pacific Ocean called “The Ring of Fire”

9. Hot Spots A rising mantle plume that melts surface rocks creating volcanoes

10. Hot spots – Evidence for Plate Tectonics The hot spot stays in one place…then the plate moves…the hot spot is still there so a new volcano forms Eventually there is a line of volcanoes – the oldest being further away from the hot spot Example is line of volcanoes from Suiko to Hawaii (Suiko is oldest, Hawaii is youngest)