1. Volcanoes

2. Prepare for Quiz Print Name: Bill Shields Lab Section: 12 TA: Ryan 1. 2. 3. 4. 5. Signature: #&$*&(*&)*(&

3. 1. Igneous rocks high in silica are dark in color. A. true B. false 2. Igneous rocks which cool slowly have coarse-grains, (large crystals). A. true B. false 3. Volcanic igneous rocks are fine-grained, (small crystals). A. true B. false 4. Extrusive igneous rocks are plutonic. A. true B. false 5. Mafic igneous rocks are low in iron and magnesium. A. true B. false

4. Increasing Fe and Mg Increasing silica (SiO 2 )

5. Mount Vesuvius

7. Pompeii

9. Types of Volcanoes *Based on type of eruption Nonexplosive – shield volcano Explosive – composite (strato) volcano Largely a function of- viscosity - dissolved gases

10. Types of Volcanoes

11. Shield Volcanoes produce Non-explosive eruptions

12. Shield Volcano: gentle slopes, layered lava flows

13. Shield Volcano: gentle slopes, layered lava flows

14. Fissure Flows

15. Basalt Flow

16. 14-16 million years ago 3500m thick 300 separate flows Covers 164,000 sq. Km

17. Composite Volcanoes Produce explosive eruptions

18. Composite (Stratovolcano) Alternating layers of lava, ash, and pyroclastics

20. Composite (stratovalcano) steep-sided, alternating layers of lava, ash, and pyroclastics

21. Mt. St. Helens – before eruption Mt. St. Helens – after eruption

25. Volcanism at Divergent Margins Few actual volcanoes, lava erupts from fissures. Molten results from decompression melting. Mafic in chemical composition.

26. Divergent Plate Boundaries

27. Pillow Lava

28. Submarine eruption of basaltic lava

29. Volcanism at Convergent Margins Volcanoes form in a line parallel to the subduction zone. Molten material is generated by heating "wet" rocks that are being subducted.

30. Convergent Plate

31. Convergent plates of the Northwest

34. Volcanism at Convergent Margins Stratovolcanoes - steep-sided - alternating layers of lava, ash and pyroclastics - explosive (due to high magma viscosity and gas content Silicic magma chemistry

36. Mantle Plumes (Hot Spots) Molten material rising from deep within the Earth. Mafic magma chemistry. Can form shield volcanoes – broad and gently sloping sides, non-violent eruptions, built by repeated layers of lava flows (Hawaiian Islands).

37. Hawaiian Islands

39. Tephra - A mixture of hot gas and fragments of all sizes

40. Ash

41. 2-64 mm Lappili

42. Block & Bombs

43. Pahoehoe Lavas

44. Lavas – A’a

45. Formation of craters and calderas

46. Resurgent Dome

48. Hazardous Volcanic Geologic Processes 1.Tephra Fall 2.Pyroclastic Flows 3.Pyroclactic Surges 4.Explosive Ejection of Ballistic Projectiles 5.Lateral Blasts 6.Lava Flows 7.Lahars

49. Tephra Fall Mixture of hot gas and Fragments less dense than air

51. Major Hazards of Tephra Fall 1.Impacts 2.Burial of structures 3.Suspension of abrasive aerosols

58. Pyroclastic Flows Avalanches of hot, dry, volcanic rock fragments and gases Denser than air 600 - 1500 O F Up to 200 mph Tends to channel into valleys

59. Causes of Pyroclastic Flow 1. High vertical eruption columns 2. Boil over 3. Disruption of hot dome

60. 1902 Eruption - Mt. Pelee St. Pierre, West Indies

63. Pyroclastic Surges Avalanches of hot, dry, volcanic rock fragments and gases Less dense than air 600 - 1500 O F Up to 200 mph Not confined to channels

64. Pyroclastic Surge Hazards Incineration Destruction by high-velocity ash-laden winds Impacts by rock or flying material Exposure to noxious gases (SOx) (CO2)

67. Explosive Ejection of Ballistic Projectiles Not constrained by wind direction Not dependent on eruptions Large projectiles thrown 1/2 mile

68. BOMBSRibbon Rotational Bread crustFusiform

69. BLOCKS

70. Lava Flows Flow controlled by topography Destructive, but not life threatening Speed related to slope and viscosity

71. Pahoehoe Flow

72. Aa - lava

73. Pahoehoe

74. ‘A’a Flow

75. Diversion Barriers

76. Lahars Rapid flow of sediment, rock, and water Channelized Twice as fast as water

77. Lahars

78. Predicting Eruptions Ground tilt and displacement Increases in surface temperature Monitoring earthquakes Changes in gas composition

79. Tragedy at Lake Nyos, Aug, 1986

81. Nyos Degassing