1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Exploring Geology Chapter 6 Volcanoes and Volcanic Hazards

2. 06.00.a Before 1980 eruption Mount St. Helens After 1980 eruption During eruption

3. Crater Vent where magma erupted Commonly a hill or mountain Can be erupted from fissure or depression, so not a hill Observe some characteristics of a volcano 06.01.a Can erupt lava or ash

4. 06.01.b Erosion of flow Fissure feeds a lava flow Hill was not over a vent (so not a volcano) Example of such a hill that is not a volcano Observe how a hill capped by volcanic rocks can form. Is it a volcano?

5. 06.01.c Shield Volcano Scoria Cone Types of Volcanoes: Part 1

6. 06.01.c Volcanic Dome Composite Volcano Types of Volcanoes II

7. 06.02.a Observe these types of eruptions Dome Lava flow Lava fountain Eruption column

8. 06.02.b2 Dissolved gas held in magma by pressure What happens when you open a soda? Under less pressure, gas forms bubbles Released gas propels eruption and forms ash How Do Gases Affect Magma? Opening top releases dissolved gas held in by pressure

9. 06.02.c How Does Viscosity Affect Eruptions? More viscous: difficult to flow and traps gas Less viscous: flows easier and gas can escape

10. 06.03.a Scoria Cones and Basalt Flows: Rock Types Nonvesicular basalt Vesicular basalt Scoria

11. 06.03.a Features of Lava Flows AA lava Lava tubes Pahoehoe lava