1. Volcanoes

2. Volcanic Hazards Smith Ch 7 Another tectonic hazard Occurrence controlled by plate tectonics

4. Types of Volcano Subduction (edge of continent) Rift (oceanic) Hot-Spot (oceanic)

5. Subduction Volcanoes Silica-rich magma, viscous –steep slopes –gassy, explosive, intermittent –ash/lava layered volcanoes

7. Mt St Helens Explosive eruptionExplosive eruption

10. Pompeii

11. Rift Volcanoes Mg & Fe-rich magma, basaltic, less viscous –Lava flows important –eruptions more continuous –gently-sloping volcanoes

12. Hot-Spot Volcanoes Like Rift volcanoes Found on oceanic “hot spots” like Hawaiian islands

13. Primary Volcanic Hazards Pyroclastic flows Airfall tephra Lava Gases

14. Pyroclastic Flows Dense clouds of hot, glowing solid lava fragments ejected from volcano –“nuee ardente” or glowing cloud flows fast downhill –30m/sec for 30-40 km especially dangerous if blast is lateral –responsible for 70% of C20th volcano deaths

15. Mt Pelee, Martinique, 1902 Eruption of Mt Pelee Nuee ardente –travelled 6 km at 33m/sec (approx. 120 km/h) –temperature: 700 degrees C –Destroyed town of St Pierre –Killed 29,000 people in 3 minutes –2 survivors in St Pierre

31. Air-fall Tephra Tephra: volcanic dusts and solids –A feature of explosive eruptions especially Dust-fall can cover 100s of Kms Dust can rise into upper atmosphere –affect climate globally

32. Mt St Helens 1980 Ash-fall over 400 km Night-like darkness in Yakima & Spokane Traffic disrupted Vehicle engines clogged Breathing problems

35. Mt Pinatubo 1991 Ash-fall disrupted 500,000 farming people Ash-fall thick for 30km radius 1 million affected by ash-fall significantly reduced global temperatures 1991-2

37. Pintaubo: crater

38. From Clark AFB

39. Clark AFB

42. After ash fall and lahar

43. Karakatoa 1883 Explosive eruption audible at 5000 km Global dustcloud created golden sunsets in 1880s

44. Tambora 1815 Killed 12,000 directly blew 1400m off the top 80,000 die in famine and disease locally global cooling caused global crop failure –riots and famine in Europe

45. Tambora 519 CE Eruption caused global cooling for a decade Global crop failures, famine, social breakdown

46. Lava Can kill, usually doesn’t –silica-rich lavas solidify too quickly –basaltic lavas move faster 15 m/s (54 km/h)

47. Nyirangongo Zaire 1977 Volcano sides crack draining lava lake –kills 72

48. Goma volcano 2002

54. Lava Ruins agricultural land –1783 eruption in Iceland causes death of 10,521 in famine

55. Mauna Kea

59. Kilauea

62. Gases Potentially fatal Carbon Dioxide the most likely to kill

63. 1979 Java eruption 142 people being evacuated from eruption asphyxiated by carbon dioxide

64. Cameroon tragedies 1984 Lake Monoun –Carbon dioxide released by eruption kills 37 1986 Lake Nyos –Carbon dioxide released by eruption kills 1746

65. 1986 Lake Nyos disaster International effort shipped inappropriate relief supplies: –22000 blankets supplied (5 each!) –1430 tents, 5000 gas masks –5000 kg of jam –11000 frozen chickens

66. Secondary Volcanic Hazards Ground deformation –Lahars –Flooding –Tsunamis

67. Ground Deformation Pre-eruption buildup of magma distorts ground –triggers avalanches, debris flows

68. Mt St Helens 1980 Triggers debris avalanche 20km down North Fork of Toutle R fills valley to 40m depth

71. Lahars Mudflows triggered by volcanoes –saturation of old and new ash-falls –melting snowpack

72. 1919 Kelut Volcano, Java 5500 killed by Lahar

73. Nevado del Ruiz 1985 Lahar brings largest loss of life in C20th since Mt Pelee, 1902 1985 Eruption generates lahar Overwhelms town of Armero, 50km downstream –3-8 m depth of mud –5000 buildings damaged –22,000 killed in minutes

74. Nevado del Ruiz 1985

79. Tsunamis Volcanic-origin tsunamis can do significant damage Karakatoa eruption 1883 –Tsunamis kill 36,000

80. Volcanic Hazards Normally have their worst effects nearby Intermittent Can have global impact –serious with large populations depending on finite global farmland