Physical Science 3/11-3/12

1. Physical Science 3/11-3/12 Volcanoes

2. New homework • Read pages 714-717 • Try problems 2,3 and 7 on pg 717

4. Volcanoes • Definition • An opening on the earth’s surface through which molten rock flows and the material that builds up around • Location Are all volcanoes equally dangerous?

6. Types of Volcanoes • Shield Volcanoes • Composite Volcanoes • Cinder Volcanoes

7. Hazards of volcanoes Ash Fall Pyroclastic Flows (Nuee Ardentes) Mud Flows (Lahars)

8. Pyroclastic flow

9. Lahars

10. Note the mud on trees

11. Hazards • Volcanic Bombs Any sizeable fragment of rock thrown from an active volcano gravel size up to boulders the size of buses

12. Volcanic Bombs

13. Hazards from the volcanic gases The expansion of gases as it is heated Produces most of the eruptive force of a ash volcano Water Vapor is the most common gas released Carbon Dioxide and Sulfur Dioxide are next

14. Lake Nyos, Cameroon, Africa 1986 Release of Carbon dioxide Since CO2 is heavier than air it hugs the ground This cloud was 100 m high Gas hazards related to volcanoes

15. Trees died by CO2 suffocation Constant release of gases

16. Tsunami

17. Volcanic Hazards • Tsunamis Means “Great Wave” Not related to tides Generated mainly by underwater earthquakes or landslides that displace a lot of water or volcanic eruption in or under the water

18. Tsunamis • Generally more than one wave • Wave is much wider than typical ocean wave (wall of water) • Travels around 500 mph in open water, slows down as it nears shore • Height increases as waves nears shore • Some waves from Krakatoa reached over 100 ft tall

19. Final Hazard • The unpredictability of some volcanoes lead some people to ignore warnings

20. Long-term volcanic benefits • Fertile soil • Volcanic products • Pumice • Sulfur • Diamonds • Metamorphic ore

21. Parts of a volcano • Vent – opening where molten rock is pushed out to the surface of earth • Magma Chamber - Chamber below volcano, holds the molten rock used in eruption • Cone – mound created from solid material released from previous eruption • Crater – hole (depression) at the top of volcano created by volcanic explosion • Caldera – depression left on top of the volcano created by the collapse of the magma chamber

23. What are the differences and similarities between: • Fumaroles • Geysers • Hot Springs • Mud-pots

24. Fumaroles

25. Fumarole An opening in the earth that emit gases May be found some distance from the from the main vent Gases are heated by the volcanic sources, travel through cracks and fractures to surface

26. Hot Springs

27. Hot Springs • Openings that are filled with water that is heated by nearby volcanic activity • The water may range from mild to scalding, and include both helpful and toxic minerals

28. Geyser

29. Geysers A hot spring with specific ideal physical arrangement that allows it to periodically erupt No convection, cold water cap over volcanically heated water

30. Mud Pots

31. Mud Pots • Similar to a hot spring • Form in places where water is scarce • Mixture of a little water and volcanic ash

32. Where are volcanoes found in the world? Convergent Divergent Other

33. One other place of volcano formation • Hot Spots • Created because a narrow stream of hot mantle raises up from the core-mantle boundary • Long lasting point of heat, stationary with respect to the plates • If formed under ocean crust, creates an island arc

35. Places where there might be a hot spot • Hawaii • Yellowstone • Iceland • Tahiti • Up to 50 places in the world

36. Types of lava Aa- Pahoehoe- Pillow lava- Difference is based location and composition

38. Homework • New Handout (Section 7.1-7.2) • Section 7.1 • All Questions except 4 Section 7.2 questions 1-6 and 10