1. CHAPTERS 18 & 20 VOLCANIC ACTIVITY AND MOUNTAIN BUILDING

2. Quiz Ch 18 Friday 11/2/07 on the following plutons laccolith sill dike caldera shield volcano composite volcano tephra pyroclastic flow hot spot

3. Chapter 18: Volcanic Activity I. Magma A. How Does Magma Form? 1. Rock is melted a) 800 o C to 1200 o C 2. Heat increases with depth a) the deeper inside Earth the hotter the temperature 3. Heat is created by the decay of radioactive elements inside Earth

4. B. Pressure 1. Pressure Increases with depth 2. Higher Pressure means higher melting temperature a) the deeper in Earth you go the more heat you need to melt rock

5. C. Water 1. Water lowers the melting point a) more water makes melting easier 2. Water is found worldwide in rocks below the surface

6. D. Types of Magma 1. Rhyolitic a) high silica content (70%) b) water-rich c) high viscosity d) high amount of trapped gases e) Very explosive eruptions f) found in the interior of continents

7. 2. Andesitic a) found along the margins of continents b) associated with subduction zones c) about 60% silica d) somewhat explosive eruptions e) medium viscosity f) medium amount of trapped gases

8. 3. Basaltic a) located in oceans and continents b) only 50% silica c) least explosive eruptions d) low amount of trapped gases e) low viscosity

9. E. Viscosity 1. The hotter the magma the lower the viscosity a) What happens to viscosity as lava cools? 2. The higher the amount of silica the greater the viscosity

10. Use your notes to answer the following 1. Will heat increase or decrease with an increase in depth in the Earth? 2. Will pressure increase or decrease with an increase in depth in the Earth? 3. List three types of magma.

11. IN YOUR NOTES COMPLETE THE FOLLOWING: PAGE 475 (2,4,5)

12. II. Intrusive Activity A. Plutons: Igneous Rock Formations 1. Batholiths a) largest intrusive formation b) form when magma cools underground before reaching the surface. c) smaller batholiths are called stocks

13. BATHOLITH

14. 2. Dikes a) form when magma squeezes in the vertical cracks of rocks andhardens b) are later exposed by erosion 3. Sills a) form when magma squeezes in the horizontal cracks of rocks and hardens b) are later exposed by erosion

15. Sill and Dike

16. Dike

17. Sill

18. 4. Volcanic Neck a) are seen when the outside of a dormant volcano erodes away b) all that is left is the solid inner core of the volcano

19. VOLCANIC NECK

20. 5. Caldera a) form when the top of a volcano collapses inside the magma chamber b) when the volcano erupts it leaves behind nothing to hold the top of the volcano up so it caves in

21. Caldera

22. 6. Laccolith a) a sill that pushes up on the rock layers forming a dome shape b) often is “mushroom” shaped

23. LACCOLITH

24. B. Plutons and Tectonics 1. Many Form at Plate Boundaries 2. Plates are melted and Magma forms

25. III. Volcanoes A. Anatomy of a Volcano 1. Vent a) an opening in the crust b) allows lava to flow out onto the Earth’s surface 2. Crater a) A bowl shaped depression at the top of a volcano b) surrounds the middle vent of a volcano

27. B. Types of Volcanoes 1. Shield Volcano a) formed by quiet eruptions b) lava flows and creates a broader flatter volcano c) ex. Hawaii

28. SHIELD VOLCANO

29. 2. Cinder Cone a) form by explosive eruptions, steep sided b) lava that flies in the air lands and cools to form layers

30. CINDER CONE

31. 3. Composite Volcano a) form when a volcano sometimes erupts quietly and sometimes erupts explosively b) layers of alternating tephra and hardened lava will make up the outside of the volcano

32. C. Volcanic Material 1. tephra: different sized lava fragments a) ash = smaller than 2mm b) lapilli = 2mm to 64mm c) Blocks = greater than 64mm, erupt as solid pieces d) Bombs = greater than 64mm, erupt as liquid and harden on the way down.

33. 2. Pyroclastic flows a) cloud of gas and dust b) caused by violent eruptions c) move at 200 km/h + d) 700 o C or greater

34. D. Where do Volcanoes Occur? 1. Plate Boundaries a) 80% at convergent boundaries b) 15% at divergent boundaries c) 5% occur away from plate boundaries 2. Hot Spots a) remember the Hawaii example

35. Chapter 20: Mountain Building I. Convergent Boundary Mountains A. Orogeny 1. processes that form all mountain ranges 2. orogenic belts occur frequently at plate boundaries

36. B. Oceanic-Oceanic Convergence 1. Creates a subduction zone 2. The end of one plate melts 3. Magma from melted plate rises to form volcanic mountains

37. C. Oceanic-Continental Convergence 1. Subduction Zone a) ocean plate sinks & melts 2. Volcanic mountains form on the continent 3. Sediments from the ocean are scraped of the ocean plate a) extreme pressure b) creates severely folded rocks (metamorphic)

38. D. Continental-Continental Convergence 1. Creates the Earth’s tallest mountain Ranges a) K2 b) Mount Everest 2. Plates do not sink under each other a) crumple up to form faults b) crust is pushed up and over the faults

39. 3. Folded Mountains also form at this type of boundary. a) anticline: A fold in rock layers that bends in an upward direction b) syncline: A fold in rock layers that bends in a downward direction.

40. SYNCLINE

41. ANTICLINE

42. II. Early Appalachian Mountains (Blue Ridge) A. Read pages 532-534 B. Answer the following: 1. When did the formation of the Appalachians begin? 2. When did the plate movements reverse in forming the Appalachians? 3. According to Figure 20-11, when did the fragment that was to become the Blue Ridge Province attached to N. America? 4. According to Figure 20-11, what does the island arc that attached 400-300 m.y.b.p. eventually become? 5. According to Figure 20-11, how long ago did ancestral Africa collide with ancestral N. America?

43. III. Other Types of Mountains A. Divergent Boundary Mountains 1. Occurs at mid-ocean ridges 2. High temperature magma is less dense a) low density causes the crust to rise and form mountains b) mountains are gently sloping

44. 3. Mid-ocean ridge rocks a) igneous b) vertical dikes c) pillow basalt

45. B. Non-boundary Mountains 1. Uplifted Mountains a) less folding and faulting b) form when the crust is heated c) lower density causes the entire section to rise d) ex. Adirondack Mountains in NY

46. 2. Fault Block Mountains a) form when large pieces of crust are tilted, uplifted, or dropped downward 3. Volcanic Peaks

47. Use your notes to answer the following 1. List two examples of non- boundary mountains? 2. What type of plate boundaries produce the world’s tallest mountain ranges? 3. Where do most volcanoes occur in the world?

48. Use your notes to answer the following 1. List three types of plutons. 2. List three types of volcanoes. 3. What causes pyroclastic flows?