Volcanic eruptions and other igneous activity

1. Volcanic eruptions and other igneous activity • Viscosity – mobility of magma (resistance to flow) • Factors affecting viscosity: • temperature • composition • silica content • dissolved gases

2. Factors affecting viscosity Low gas content High viscosity (low mobility) Low temp High SiO2 High gas content Low viscosity (high mobility) High temp Low SiO2 Volcanic eruptions and other igneous activity

3. Importance of dissolved gases High violence eruption Low gas content High pressure High viscosity (low mobility) Low violence eruption High gas content Low pressure Low viscosity (high mobility) Volcanic eruptions and other igneous activity

4. Materials extruded during an eruption • Lava flows • pahoehoe flows • aa flows • block lavas • pillow lavas • Gases • Pyroclastic materials accdg to size • ash and dust (welded tuff) • pea to walnut sized (lapilli, cinders) • blocks • bombs • Pyroclastics accdg to texture • scoria (from basaltic magma) • pumice (from felsic magma) Volcanic eruptions and other igneous activity

5. Materials extruded during an eruption Lava flows – pahoehoe vs aa flows Pahoehoe flows Volcanic eruptions and other igneous activity

6. Materials extruded during an eruption Lava flows – pahoehoe vs aa flows aa flows Volcanic eruptions and other igneous activity

7. Materials extruded during an eruption Hardened pahoehoe flows = lava tubes Volcanic eruptions and other igneous activity

8. Materials extruded during an eruption Block lavas Volcanic eruptions and other igneous activity

9. Materials extruded during an eruption Pillow lavas Volcanic eruptions and other igneous activity

10. Materials extruded during an eruption Pillow lavas The study of pillow lavas is important in reconstructing Earth’s geologic history. Can you tell why? Volcanic eruptions and other igneous activity

11. Materials extruded during an eruption Gases Water vapor 70% CO2 15 Nitrogen 5 Sulfur dioxide 5 (low amounts of) Chlorine Hydrogen Argon Why is the study of volcanic gases very important? Volcanic eruptions and other igneous activity

12. Materials extruded during an eruption Gases Volcanic eruptions and other igneous activity

13. Materials extruded during an eruption Gases Volcanic eruptions and other igneous activity

14. Materials extruded during an eruption Pyroclastic materials – welded tuff Volcanic eruptions and other igneous activity

15. Materials extruded during an eruption Pyroclastic materials – welded tuff Volcanic eruptions and other igneous activity

16. Materials extruded during an eruption Pyroclastic materials – welded tuff Volcanic eruptions and other igneous activity

17. Materials extruded during an eruption Pyroclastic materials – welded tuff Volcanic eruptions and other igneous activity

18. Materials extruded during an eruption Pyroclastic materials – lapilli or cinders From Vesuvius Volcanic eruptions and other igneous activity

19. Materials extruded during an eruption Pyroclastic materials – blocks Volcanic eruptions and other igneous activity

20. Materials extruded during an eruption Pyroclastic materials - bombs Volcanic eruptions and other igneous activity

21. Materials extruded during an eruption Pyroclastic materials (accdg to texture) - scoria • Basaltic magma • Darker • Denser Volcanic eruptions and other igneous activity

22. Materials extruded during an eruption Pyroclastic materials (accdg to texture) - pumice • Silica-rich magma • Lighter color • Less dense Volcanic eruptions and other igneous activity

23. Anatomy of a volcano Volcanic eruptions and other igneous activity

24. Anatomy of a volcano - caldera Volcanic eruptions and other igneous activity

25. Anatomy of a volcano - caldera Volcanic eruptions and other igneous activity

26. Anatomy of a volcano - caldera Volcanic eruptions and other igneous activity

27. Anatomy of a volcano – parasitic cones Volcanic eruptions and other igneous activity

28. Anatomy of a volcano – fumaroles Volcanic eruptions and other igneous activity

29. Volcano types – shield volcano • fluid basaltic lavas, often a few meters thick • broad, slightly domed structure • very few pyroclastic ejecta • lava tends to be more viscous as volcano matures Volcanic eruptions and other igneous activity

30. Volcano types – shield volcano Mauna Loa and Mauna Kea (upper white smudge) are 2 (of 5) overlapping shield volcanoes that make up Hawaii’s Big Island. Volcanic eruptions and other igneous activity

31. Volcano types – shield volcano Mauna Loa is over 9 km high (more than Everest’s 8.7km) Volcanic eruptions and other igneous activity

32. Volcano types – cinder cones • built from ejected lava fragments known as cinders or scoria • ash to walnut-sized ejecta Volcanic eruptions and other igneous activity

33. Volcano types – cinder cones • single eruptive episode = small cones • lava pipe is often immediately sealed with congealed lava • lava flows seldom happen; only at base, away from summit crater Volcanic eruptions and other igneous activity

34. Volcano types – composite cones • large, nearly symmetric structure of both lava and pyroclastic deposits • silica-rich magma travels only a short distance • gas-rich magma often produces violent eruptions Volcanic eruptions and other igneous activity

35. Volcano types – composite cones • steep summit with gently sloping flanks are due to lava flows • when young, lava tends to be more viscous, hence traveling farther to make a bigger base • mature volcanoes produce more viscous lava with increase the summit’s angle Volcanic eruptions and other igneous activity

36. Volcano types – hazards of composite cones sudden, often unexpected eruptions Volcanic eruptions and other igneous activity

37. Volcano types – hazards of composite cones Nuee ardente (glowing avalanches) Volcanic eruptions and other igneous activity

38. Volcano types – hazards of composite cones Lahar (mudflows of pyroclastic material) Volcanic eruptions and other igneous activity

39. Other volcanic landforms - Calderas Crater lake-type caldera Volcanic eruptions and other igneous activity

40. Other volcanic landforms - Calderas Hawaiian-type caldera Volcanic eruptions and other igneous activity

41. Other volcanic landforms - Calderas Yellowstone-type caldera Volcanic eruptions and other igneous activity

42. Other volcanic landforms – Fissure eruptions and basalt plateaus Fissure eruptions Volcanic eruptions and other igneous activity

43. Other volcanic landforms – Fissure eruptions and basalt plateaus Basalt plateaus Volcanic eruptions and other igneous activity

44. Other volcanic landforms – Lava dome Volcanic eruptions and other igneous activity

45. Other volcanic landforms – Volcanic pipes Kimberlite diamond mines are volcanic pipes Volcanic eruptions and other igneous activity

46. Other volcanic landforms – Volcanic necks Volcanic necks are exposed pipes (erosion has long since removed the surrounding volcanic structure) Volcanic eruptions and other igneous activity

47. Intrusive igneous activity – plutons • According to shape • Tabular • Massive • According to orientation • Discordant • Concordant • Dikes – tabular, discordant • Sills – tabular, concordant • Laccoliths – tabular, concordant • Batholiths Volcanic eruptions and other igneous activity

48. Other volcanic landforms – Dikes Volcanic eruptions and other igneous activity

49. Other volcanic landforms – Sills Volcanic eruptions and other igneous activity

50. Other volcanic landforms – Sills Volcanic eruptions and other igneous activity