1. Volcanic Eruptions

2. Mafic Lava  Dark colored  Rich in magnesium and iron  Formed from oceanic crust  Cools rapidly

3. Felsic Lava  Light colored  Rich in silica  Formed from continental crust

4. Eruptions  Composition of lava determines the force of the eruption

5. Oceanic Eruptions  Erupt on the ocean floor and oceanic islands  Mafic lava  Very hot  Very thin (watery)  Flows easily

6. Continental Eruptions  Erupt on the land  Felsic lava  Cooler  Thicker  Contains large amounts of gases  Carbon dioxide and water vapor  Explosive

7. Mafic Lava  Pyroclastic material (tephra)-rock fragments ejected from volcanoes  Volcanic ash- less than 2 mm  Volcanic dust- less than.25 mm  Both can travel around the Earth in the atmosphere

8. Volcanic Cones  Piles of volcanic material around the vent

9. Volcanic cones  Shield cones  Cover wide areas  Broad at the base  Gentle slope  Quiet eruptions  Example Hawaiian Islands

10. Shield cones

11. Volcanic cones  Cinder cones  Explosive eruptions  Very steep slopes  Rarely more than a few hundred meters high

12. Cinder cones

13. Volcanic cones  Composite cones  Develop into high volcanic mountains  Alternating types of eruptions  Examples: Mount Fuji, Mount Hood, Mount St. Helens

14. Composite cones

15. Crater  Funnel shaped pit at the top of a volcanic vent

16. Caldera  Large basin shaped depression caused by an explosive eruption  Magma chamber below a vent, causing the volcanic cone to collapse

17. Predicting Volcanoes  Earthquakes  Temperature changes in rock around vent  Bulging of the surface of the volcano  Change in gases given off