1. volcanoes

2. Volcano
Definition: A mountain formed of lava or pyroclastic material.

3. Redoubt Volcano
Aleutian Islands, Alaska

4. Factors affecting eruptions
Viscosity – a substance’s resistance to flow
Thickness of lava depends on it’s chemical composition
Silica increases viscosity
Rhyolitic (contains Rhyolite) - high silica content = high viscosity
Basaltic (contains Basalt) – low silica content = low viscosity

5. Factors affecting eruptions
Viscosity – a substance’s resistance to flow
Thickness of lava depends on it’s chemical composition
Silica increases viscosity
Rhyolitic (contains Rhyolite) - high silica content = high viscosity
Basaltic (contains Basalt) – low silica content = low viscosity

6. Factors affecting eruptions
Viscosity – a substance’s resistance to flow
Thickness of lava depends on it’s chemical composition
Silica increases viscosity
Rhyolitic (contains Rhyolite) - high silica content = high viscosity
Basaltic (contains Basalt) – low silica content = low viscosity

7. Volcanic material Gases Composition 70% water vapor 15% Carbon Dioxide
5% Nitrogen
5% Sulfer
Other gases – Chlorine, Hydrogen, Argon

8. Dissolved gases Mostly water and carbon dioxide
High silica Rhyolite traps more gas
Low silica Basalt releases gas
Trapped gases create pressure that leads to more
kilauea/update/archive /2011/Mar/Overflight_ b.mov

9. Volcanic materials Lava Flows
Pahoehoe – very fluid, basaltic, looks rope-like when it cools
gov/kilauea/update /archive/2011/Mar/ _torr_2609 _trim.MOV

10. Volcanic materials
AA (ah-ah) – rough, jagged, very slow moving

11. Volcanic material Pyroclastic Materials
Particles produced by volcanic eruptions
Ejected from the vent
Includes:
Dust and Ash (less than 2mm in dia.)
Cinders (2mm – 64mm in dia.)
Blocks and Bombs
greater than 64mm
Can weigh tons
Blocks are hardened
Bombs are molten

12. Ash plume

13. Volcanic ash

14. Ash cloud

15. cinders

16. Volcanic block

17. Volcanic block

18. Volcanic bombs

19. Types of Volcanoes Anatomy of a volcano
Crater – steep walled depression at the summit

20. Types of Volcanoes Anatomy of a volcano
Fissure – crack in the Earth’s crust that magma moves through

21. Types of Volcanoes Anatomy of a volcano Pipe
tube through a volcano that magma moves through

22. Types of Volcanoes Anatomy of a volcano
Vent – opening on the surface where lava flows or is ejected
gov/kilauea/update /archive/2011/Mar/ SpatterVents_04Aug 2011.mov

23. Types of Volcanoes Anatomy of a volcano
Magma Chamber – A large reservoir of magma within the Earth’s crust

24. Cinder cone SC Volcano Arizona, Stromboli Italy
Cinder sized fragments ejected into the air, harden and collect into a steep mound
Eruptions can last from several days to several years
When eruptions stop, magma in the pipe and chamber hardens and the volcano never erupts again
Several cinder cones can form fields others can form on the sides of larger volcanoes

25. Cinder Cone

26. Cinder cone (new Guinea)

27. Stromboli, Italy

28. Shield volcano (Hawaiian islands, galapagos islands
Broad, slightly domed
Produced by the build-up of fluid, basaltic lava

29. Shield Volcano, mauna loa hawaii

30. Shield volcano (Hawaiian islands, galapagos islands
Hot Spots – locations where a volcanic plume rises to the surface, far away from plate boundaries, usually under oceans to build island chains as the plate moves

31. Hawaiian Island progression is toward Northwest as the pacific plate moves

32. Composite cones (mt st helens)
Large symmetrical structures composed of layers of lava and pyroclastic materials
Silica rich, viscous lava
Most explosive, ejects large amounts of pyroclastic materials

33. Mt. St. helens after eruption

34. Composite cones (mt st helens, krakatoa, mt ranier)
Ring of Fire – string of volcanoes around the rim of the Pacific Plate

35. Composite cones (mt st helens, krakatoa, mt ranier)
Pyroclastic flow: Very hot clouds of pyroclastic materials and gases rushing down slopes at speeds up to 200 Km/hr

36. Composite cones (mt st helens, krakatoa, mt ranier)
Lahar: Destructive mudflows created from water-saturated volcanic debris

37. Other volcanic landforms
Caldera: large depression formed by collapsing volcanoes (ie…Crater Lake Oregon, Yellowstone Park Wyoming)

38. Other volcanic landforms
Volcanic Neck: hardened magma remaining after the volcanic cone erodes away

39. Other volcanic landforms
Volcanic Pipe: remain years after a volcano becomes extinct (diamonds can form there)

40. Other volcanic landforms
Lava Plateaus: deposits of volcanic material flowing from fissures or rifts

41. Global affects of volcanic activity
Ash ash.shtml
can spread over wide areas and affect temperatures, soil composition, drainage, etc…
can be thick enough to block out the sun
Is extremely abrasive and can be destructive to machinery( small enough to pass through air filters and get into car engines)
Can smother plants interrupting photosynthesis

42. Global affects of volcanic activity
Ash (continued)
Can disrupt air traffic
Has been known to disable aircraft in flight

44. Mt st helens

46. Mt pinatubo ash blocking sunlight

47. Pompeii with mt vesuvius in background
Pompeii with mt vesuvius in background. The pyroclastic flow buried the city and its inhabitants

48. Victims of mt Vesuvius

50. Gases: Mt Pinatubo sulfer dioxide cloud nine days after eruption

51. Lahar/mudslides and erosion from mt st helens

52. Scientists measuring erosion from mt st helens lahar

53. Mt st helens lahar damage

54. Lava flow damage

55. Newberry volcano lava flow