1. Volcanic Landforms Processes and Hazards

2. Volcanic Landforms 1.Intrusive Igneous Forms 2.Extrusive – Basalt Landforms 3.Extrusive – Composite volcanoes 4.Extrusive – Rhyolite landforms

3. 1. Intrusive Igneous Forms Magma solidified at great depth (so mineral sizes are large) Plutons (individual magma chambers) Batholiths (merged magma chambers)

5. Pluton seen because of glacial erosion, Chile

6. Brandberg, Western Namibia Intrusive igneous rocks are often more resistant to erosion, so they are topographic highs

7. Plutons (individual magma chambers) Batholiths (merged magma chambers) Laccolith (bubble up strata) Dikes – vertical magma cutting through Sill – horizontal magma inserted between Large Small

9. Dike, Spanish Peaks, Colorado more resistant than surrounding sediment, so stand out

10. Dike, Picture Gorge

11. Shiprock (Tse bi Dahi, Rock With Wings), New Mexico is the classic example of a volcanic neck (base of composite volcano, so deep that is intrusive rock) Over time, the less resistant rock (i.e., pyroclasts and less consolidated lava flows) comprising the flank of the volcano is eroded away leaving the resistant neck exposed in relief. Volcanic Neck. Dike

12. Classroom Resource Tse bi Dahi Rock With Wings Shiprock Volcanic Neck

13. Viscosity Organization Extrusive – Basalt Landforms Extrusive – Composite volcanoes Extrusive – Rhyolite landforms

14. More Viscous = More Explosive Classroom Resource

15. 2. Extrusive – Basalt Landforms Basalt Flow Flood Basalts Cinder Cone Shield Volcano Shield & Cinder Cone – from basalt eruptions Later: Composite volcano

16. Basalt flows will travel great distances and slope angles will reflect low viscosity.

17. Classroom Resources Recent Hawaii Eruptions (NPS) A year of pahoehoe Spatter Cone

18. Low viscosity releases trapped gases easily, so not explosive.

19. Classroom Resources Etna Tourist Office No Lives Lost

20. Different Textures, Same Basalt Rock Pahoehoe a’a

21. Lava Tubes – so fluid that inside keeps moving & creates caves Classroom Resource Lava tube breakout

22. Lava Tube, Hawaii near Flagstaff, AZ Mt St. Helens, OR

24. Buries old topography

26. Cinder Cones SP Crater, AZ

27. Cinder drops out (like hour glass)

28. Cinder Cone Developing

29. Largest drop out first

30. Largest Clasts: Volcanic Bombs Classroom Resource Cinder Cone Bombs

31. Crater: depression at top formed by force of eruption

32. Owens Valley, Calif

33. Very common in Arizona: especially S.F. Volcanic Field

34. Sunset Crater, AZ

35. Shield Volcanoes Isabela Island, Galapagos

36. Hawaii built from Shield Volcanoes

37. Weight of new lava has depressed the crust around Hawai’i Moat ~ 5000 m Below Sea Level

39. Mauna Loa: note gentle profile from fluid basalt flows

40. Mauna Kea

41. Often have Summit Caldera – from collapse as lava flows away

42. 3. Extrusive – Composite Volcanoes Mt Ararat, Armenia

44. Sit above Subduction Zones Fuji Egmont

45. Extraordinarily Dangerous from Nova

48. Future Disaster: Popocatepetl, next to Mexico City & Puebla

49. Composite Volcano

50. Online Animations Volcanic Hazards http://serc.carleton.edu/NAGTWorkshops/vis ualization/collections/volcano.html

51. Classroom Resources Nuee Ardente (also called glowing avalanche, pyroclastic flow) Set to music (www.mvo.ms) Soufriere, Montserrat

52. Nuee Ardente (Glowing Avalanche or pyroclastic flow)

53. Pompeii, Italy Mt. Vesuvius

56. Volcanic Ash

57. Debris Avalanche

59. Mt St. Helens Before Eruption

65. Classroom Resource Lahaar, Mt St. Helens Fly Over

70. Mt Mazama (could be Rainier)

71. Caldera – from collapse after lava has “evacuated” from magma chamber Crater Lake

72. Mt Hood (my bet to go next)

73. Mount Pinatubo

75. Classroom Resources

76. Arizona has San Francisco Peaks & Mt Baldy

77. Classroom Resource San Francisco Peaks (made by Simpkin, ASU)

78. 4. Extrusive – Rhyolite Landforms Small Eruptions: Rhyolite Domes, Mt Elden Rhyolite so viscous has trouble flowing, so piles up in dome shape

79. Many Rhyolite Domes near Mono Lake, Calif

80. Mammoth Lakes, still active evidence: carbon dioxide

81. Classroom Resources After major eruption of composite volcano, will often start to rebuild with rhyolite domes

85. Arizona has many rhyolite caldera super eruptions (17-27 myr ago) Superstition Mtns Chiricahua Mtns

86. Toba – almost did us in

88. Imagery seen in this presentation is courtesy of Ron Dorn and other ASU colleagues, students and colleagues in other academic departments, individual illustrations in scholarly journals such as Science and Nature, scholarly societies such as the Association of American Geographers, city, state governments, other countries government websites and U.S. government agencies such as NASA, USGS, NRCS, Library of Congress, U.S. Fish and Wildlife Service USAID and NOAA.c