1. Bell Ringer Wednesday 12/2/09 Explain P waves, S waves, and L waves? At what plate boundaries can volcanoes occur?

2. Volcanoes

3. Volcanism Volcanism – activity that includes the movement of magma toward or onto the surface of the Earth Magma – liquid rock

4. Volcanism Lava – magma that erupts onto Earth’s surface Vent – opening through which molten rock flows onto the surface

5. Volcanism Volcano – the vent and volcanic material that builds up on the Earth’s surface around the vent

6. Convergent Volcanic Zones Subduction Zones – where oceanic crust goes beneath continental crust

7. Convergent Volcanic Zones Pacific Ring of Fire – a major zone of active volcanoes caused by subducting plates encircling the Pacific Ocean

8. Convergent Volcanic Zones Island Arc – string of volcanic islands from a deep ocean trench caused by an oceanic crust subducting under another oceanic crust

9. Divergent Volcanic Zones Mid-Ocean Ridges – where tectonic plates are moving apart under the ocean (i.e. Iceland)

10. Divergent Volcanic Zones Rifts – long, narrow cracks formed at mid- ocean ridges Fissures – cracks through which lava flows

11. Hot Spots Hot Spots – area of volcanism within a lithospheric plate

12. Hot Spots Hot spots remain stationary while the lithospheric plate moves Example: Hawaiian Islands

13. Types of Lava Mafic lava – oceanic crust lava Felsic lava – continental crust lava Pahoehoe – ropey lava

14. Types of Lava Aa – sharp, blocky lava

15. Types of Lava Pillow lava – round shape lava from ocean

16. Volcanic Rock Fragments Tephra – rock fragments from volcano Lapilli – “little stones” (large tephra)

17. Volcanic Features 3 types of Volcanic Cones (see fig. 9-p. 744)

18. Shield Cone Broad base and gentle slopes Layers of hot mafic lava Hawaiian islands

19. Cinder Cone Narrow base and steep slope Layers of tephra Sunset Crater

20. Composite Cone Both broad and steep Alternating layers of lava and tephra Mount St. Helens

21. Craters and Calderas Crater – funnel shaped pit at the top of the volcano

22. Craters and Calderas Caldera – collapse of the volcanic cone creates a large, basin-shaped depression

23. Predicting Volcanic Eruptions Clues –Seismographs monitor small earthquakes –Temperature changes within the rock –Slight bulging of volcano surface