1. V. Volcanoes and Volcanism A. Mafic Volcanism and Volcanic Rocks B. Felsic Volcanism and Volcanic Rocks A. Mafic Volcanism and Volcanic Rocks B. Felsic Volcanism and Volcanic Rocks

2. Mafic Volcanism 6. Characteristics of formations  5. Types of Rocks  4. Types of eruptions which controls  3. Type of lava which controls  2. Source of lava which controls  1. Plate tectonics 

3. 1. 2. Source of Lava 3. Types of Lava Partial melting of mantle Partial melting of dry mantle At mantle plumes or Divergent plate boundaries Types of lava Basaltic Hot (>1000 o C) Non-Viscous (runny, flows easily) “Dry” (no H 2 O or C0 2 )

4. Non-explosive Lava flows, streams, ponds, floods Fountains Spatter cones Pyroclastic eruptions 4. Types of Eruptions

6. Basalt Figs. 4.9, 4.11, 4.17, 4.18 ‘A’a Pahoehoe Vesicular Basalt Pillow Basalt Columnar Jointing Obsidian Volcanic Glass 5. Types of Rocks Composition and Texture

8. 6. Characteristic Formations Flood basalts and basalt plateaus Shield volcanoes Cinder cones Fissures Through Crust Hawaii Cinder Cone Calderas atop of Kilauea Shield

9. Devil’s Post Pile, California Columnar Jointing in basalt floods As lava floods cool and solidify The basalt contracts and Splits into hexagonal columns

10. Columnar Jointing Columnar jointing may occur in volcanic stocks (large cylindrical core of volcanoes) Devils Tower, Wyoming

11. Pillow Basalts Evidence of submarine eruptions

12. Volcanic Hazards Map out rift zones Use topography to determine flow direction

13. Rift Zones and Lava Flows Kilauea, Hawaii

14. Hawaii Hazards

16. B. Felsic Volcanism 6. Characteristics of volcanoes  5. Types of Rocks  4. Types of eruptions  3. Type of lava  2. Source of lava  1. Plate tectonics 

17. 1, 2. Plate tectonics and Sources of Lava Partial melting at Subduction Zone Partial melting of continental crust Convergent plate boundaries Fig. 3.24

18. 3. Types of Lava Felsic Cool (<800 o C) Viscous Gaseous (H 2 O, CO 2 )

19. 4. Types of Eruptions Mt. St. Helen’s Cascade Range Explosive Pyroclastic Flows and surges Lahars (saturated pyroclastics) Fig. 4.1 Fig. 4.20

20. 5. Types of Rocks Composition and Texture 1mm Andesite (and Rhyolite) Pumice (quenched glass froth) Porphyritic Texture (partial crystallization and extrusion) Welded Tuffs (welded pyroclastics) Breccias (welded, coarse, angular pyroclatics)

21. 6. Characteristics of Volcanism Lava Domes Composite Volcanoes Layers of Pyroclastics (or tephra), ash and Lava flows Pyroclastic Layers

22. 1 mile Mt. St. Helen’s Before and After

24. Vocanic Hazards Volcanic Earthquakes Directed Blast Tephra Volcanic Gases Lava Flows Pyroclastic Flows and Surges Lahars Debris Avalanches, Landslides, and Tsunamis

25. Convergent Plate Boundaries  Composite Volcanoes of Andesite Mid-Ocean Ridges  Pillow basalts forming new oceanic crust Hot spots in oceans  Forming shield volcanoes Hot spots and divergent boundaries on continents  Forming flood basalts, shield volcanoes (maybe some composite volcanoes) Locating Volcanoes and Volcanism