1. Volcanoes and Volcanic Hazards

2. View From Space - Klyuchevskaya, Russia

3. Cleveland Volcano, Alaska

4. Mount Etna From Space

7. Mount Etna

8. Shiveluch, Russia

9. Magma – molten rock beneath the surface Lava – molten rock on the surface

10. Where Does Magma Come From? Earth’s interior is hot (25 C/km near surface = 1000 C at 40 km) Pressure inhibits melting –Mantle is solid –Never far below melting point Volcanoes fed by small pockets 0-100 km deep –Rising hot material may melt –Water can lower melting point

11. Why Igneous Rock Classification Matters Silica Content = Viscosity Silica Content Governs Violence of Eruptions –Silica Poor (Basalt): Fluid lavas, generally little explosive activity –Intermediate Lavas (Andesite): Pasty lavas, explosive eruptions common –Silica-Rich Lavas (Rhyolite): Extremely viscous lava and explosive eruptions

12. Basalt (45-52% SiO 2 ) Slightly modified planetary raw material Derived directly from mantle –Oceanic crust –Hot Spots and Flood Basalts –Oceanic volcanic arcs –Early stage of continental volcanic arcs –Rift zones with rapid spreading Fluid lava with little explosive activity Shield volcanoes, Cinder Cones

13. Plate Tectonics and Volcanoes

14. A Cinder Cone: Wizard Island, Crater Lake, Oregon

15. Paricutin, Mexico 1943-1952

16. Shield Volcano: Haleakala, Hawaii

17. Andesite (52-66% SiO 2 ) Mixture of mantle material and continental crust Continental volcanic chains Pasty lava with significant explosive activity Stratovolcanoes

18. Plate Tectonics and Volcanoes

19. Stratovolcano: Mount Shasta, California

20. Stromboli

21. Rhyolite (>66% SiO 2 ) Mostly remelted continental crust Settings where magma has a long time to react with continental crust –Late stage of continental volcanic arcs –Slow-spreading Continental Rifts –Continental Hot Spots (Yellowstone) Catasrtophic explosive activity common Obsidian domes, magma chamber collapses

22. Lava Dome, California

23. Some Igneous Rocks Are Named on Textural Criteria Pumice - Porous Obsidian - Glass Tuff - Cemented Ash Breccia - Cemented Fragments

24. Classes of Eruption Effusive Icelandic Hawaiian Explosive Strombolian Vulcanian Plinian Caldera-Forming (Ultra-Plinian) Phreatic:

25. Classes of Eruption TypeLavaVolcanoEffects IcelandicBasaltNone or ShieldFissure Flows HawaiianBasaltShield StrombolianBasalt- Andesite Small Stratovolcano Mild, Continuous VulcanianAndesiteStratovolcanoLarge eruption cloud PlinianAndesite – Rhyolite StratovolcanoPyroclastic Flows Caldera-FormingRhyoliteStratovolcano or None Large Pyroclastic Flows PhreaticAny Steam Blast

26. Products of Eruptions Lava Flows Pyroclastic Debris Bombs Lapilli Ash Mudflows Landslides Gases Steam Carbon Dioxide H 2 S SO 2 HCl HF

27. Environmental Hazards of Volcanoes Pollution SO2, HCl in Water Lava Flows Falling Ejecta Ash Falls Building Collapse Crop Destruction Mudflows Direct Damage (Colombia, 1985) Floods (Several Types) Blast (Mt. St. Helens, 1980) Pyroclastic Flow (St. Pierre, 1902) Gas (Lake Nyos, Cameroon, 1986)

28. Volcanic Hazards, Congo

29. Nyiragongo, Congo At least 34 eruptions since 1982 Semi-permanent lava lake Area accounts for 40% of Africa’s historic eruptions Steep-sided but unusually fluid lava: unique 1977: Lava lake drains at night, killing 70- hundreds 2002: Lava invades city of Goma: 400,000 evacuated, 45 killed, 4500 buildings destroyed, 120,000 homeless

30. Pyroclastic Flow or Nuee Ardente (French: Fiery Cloud)

31. Welded Tuff, California

32. How Calderas Form

33. Crater Lake, Oregon

34. Mount Mazama: After

35. Mount Mazama: Before

36. Jemez Caldera, New Mexico

37. Valles Caldera, New Mexico

38. Tuff, Valles Caldera, New Mexico

39. Santorini (Thera), Greece

41. Santorini, Greece

43. Ash Layer, Santorini

44. Ash Layers, Santorini

45. What Really Destroyed the Minoan Civilization

47. Volcanic Explosivity Index VEIClassificationDescriptionPlume Ejecta volume FrequencyExample 0Hawaiiannon-explosive< 100 m< 10 4 m³dailyMauna Loa 1 Hawaiian Strombolian gentle100-1000 m> 10 4 m³dailyStromboli 2 Strombolian Vulcanian explosive1-5 km> 10 6 m³weeklyGaleras 1993 3Vulcanian /Peleansevere3-15 km> 10 7 m³yearlyLassen 1915 4Pelean/Pliniancataclysmic10-25 km> 0.1 km³≥ 10 yrs Soufrière Hills 1995 5Plinianparoxysmal> 25 km> 1 km³≥ 50 yrsSt. Helens 1980 6Plinian/Ultra-Pliniancolossal> 25 km> 10 km³≥ 100 yrsPinatubo 1991 7Plinian/Ultra-Pliniansuper-colossal> 25 km> 100 km³≥ 1000 yrsTambora 1815 8Ultra-Plinianmega-colossal> 25 km> 1,000 km³≥ 10,000 yrs Toba (73,000 BP)

48. Collapsing Volcanoes – Mount Rainier

49. Shastina and Landslide Deposit

50. Mount Shasta and Landslide Deposit

51. Collapsing Volcanoes - Hawaii

52. Volcanoes and Climate Stratospheric Ash Sulfuric Acid Aerosols –Colorful sunset effects –Large amounts can block sunlight Carbon Dioxide

53. Dating Large Remote Eruptions Historical Records of Unusual Cold Optical Effects Persistent “Dry Fog” Frost Rings in Trees

54. Frost Ring, 536 AD, Mongolia

55. Recorded Large Distant Eruptions 1627 BC: Thera? 536 AD: Krakatoa? 626: Unknown 934: Eldgja, Iceland 1258: Unknown 1783: Laki, Iceland 1815: Tambora, Indonesia

56. Tambora 1815 1816: “Year Without A Summer” 100 cubic km of ash erupted Global sunset color effects for months New England –Snow in June and August, Frost in July –Exodus to Midwest Europe: High prices, food riots

57. Tambora

58. Flood Basalts Siberian Traps and Permian Mass Extinction? High Sulfur Content –Aerosols may block significant sunlight –Surface crust may trap sulfur

59. Supervolcanoes? Magma Chamber Collapse (Yellowstone?) –Destruction of crops –Destruction of high technology –Economic Disruption –Climatic Effects Flood Basalts –Climatic Effects –Toxicity

60. Long Valley Caldera

62. Bishop Tuff

63. Compaction of Bishop Tuff

64. Toba, Sumatra