1. Chapter 18 Earth science Alex Newell 3/1/10

2. Volcanic activity Magma Types of magma Viscosity Intrusive activity Plutons and tectonics Volcanoes Volcanic material

3. Magma All volcanoes are fueled by magma deep beneath Earth’s surface

4. Types of magma Basaltic magma- Basaltic magma- has the same composition as basalt

5. Andesitic magma Has the same composition as andesic

6. Viscosity The viscosity of magma and of its surface counterpart, lava, depends on both temperature and composition

7. Plutons Intrusive igneous rock bodies

8. Laccoliths A mushroom- shaped pluton with a round top and flat bottom

9. Volcanoes Lava erupts through an opening in the crust called a vent

10. Volcanoes At the top of a volcano, around the vent, is a bowl shaped depression called a crater

11. Types of volcanoes Shield volcano- a mountain with a broad, gently sloping sides and a nearly circular base Shield

12. Cinder-cone volcanoes Forms when material ejected high into the air falls back to Earth and piles up around the vent

13. Composite volcanoes Form when layers of volcanic fragments alternate with lava

14. Volcanic material Rock fragments thrown into the air during a volcanic eruption are called tephratephra

15. Pyroclastic flow Rapidly moving volcanic material