volcanoes

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 • http://hvo.wr.usgs.gov/kilauea/update/archive/2011/Mar/Overflight_20110808b.mov

9. Volcanic materials • Lava Flows • Pahoehoe – very fluid, basaltic, looks rope-like when it cools http://hvo.wr.usgs.gov/kilauea/update/archive/2011/Mar/20110923_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 • http://hvo.wr.usgs.gov/kilauea/update/archive/2011/Mar/SpatterVents_04Aug2011.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, maunaloahawaii

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 (mtsthelens) • 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 (mtsthelens, krakatoa, mtranier) • Ring of Fire – string of volcanoes around the rim of the Pacific Plate

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

36. Composite cones (mtsthelens, krakatoa, mtranier) • 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 http://geology.com/articles/volcanic-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. 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