1. VOLCANOES WRITE THE UNDERLINED WORDS INTO YOUR NOTES

2. FACTORS AFFECTING MAGMA Heat and depth Pressure Water content

3. FROM THE PREVIOUS SLIDE Think about how each factor might affect the melting point of a rock. Does the factor make it easier or harder to melt the rock?

4. ANSWERS Heat- Increasing depth increases heat which melts the rocks. Must be >1600C for most rocks. Pressure- Increasing pressure increases the melting point of a rock. Water- More water present decreases the melting point. Most rocks are molten when the reach the mantle.

5. FACTORS AFFECTING ERUPTIONS Composition of magma Dissolved gasses Viscosity

6. QUESTIONS- USE TABLE 1 PG. 287 How does magma composition relate to viscosity? How does magma composition relate to gas content? How do viscosity and dissolved gasses affect volcanic eruptions?

7. ANSWERS Silica content determines viscosity. More silica = more viscosity More silica = more dissolved gas Increasing both viscosity and dissolved gas increases the explosivity of an eruption.

8. JAPAN VOLCANO volcano clip