Hawaiian tephra


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Hawaiian tephra

  1. 1. Hawaiian Islands Teprha
  2. 2. Source for photos and explantions on the web <ul><li>http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html </li></ul>
  3. 3. Plinian Eruption Column
  4. 4. <ul><li>TEPHRA: Any volcanic product ejected into the air. </li></ul><ul><li>Includes pumice, ash, spatter and more! </li></ul>
  5. 5. Volcanic Ash
  6. 6. PUMICE
  7. 7. <ul><li>Tephra may either be shot into the air ballistically or carried upwards by the convecting column and blown downwind </li></ul>
  8. 8. Eruption Column and Cloud
  9. 9. <ul><li>Ballistically ejected particles like blocks, bombs, and spatter tend to land near the vent and build cones. </li></ul>
  10. 10. Ballistic Spatter Explosion at Night. Notice the Parabolic Path of the Spatter.
  11. 11. <ul><li>Convectively carried material like ash, pele’s hair, light pumice blocks, and reticulite are carried far from the vent by the ash cloud. Deposits from ash clouds get finer away from the vent. </li></ul>
  12. 12. VOLCANIC ASH
  13. 13. Tephra is blown by Winds
  14. 14. <ul><li>The explosivity of a volcano is related to gas expansion and the viscosity of the magma. </li></ul><ul><li>Abundant gas that expands rapidly provides the force </li></ul><ul><li>Viscosity of magma is the container. If the bubbles escape easily there is little fragmentation. Trapped bubbles explode causing fragmentation. </li></ul>
  15. 15. Explosivity Index
  16. 16. TEPHRA: PYROCLASTIC PRODUCTS Pyroclastic Products are Called Tephra Tephra are named first for size, then for texture. >64 millimeters: Bombs and Blocks (Ballistic) (includes ribbon bombs, teardrop bombs, spatter bombs, pumice bombs–blocks, lava blocks, and lithic blocks) 2 to 64 millimeters: Lapilli (includes pumice, cinder, scoria, reticulite, pele’s tears, pele’s hair, limu o Pele, accretionary lapilli, and lithic lapilli) < 2 millimeters: Ash (includes ash, pele’s hair, limu o Pele,)
  17. 17. <ul><li>Most of the gas that drives eruptions is water that turns to steam bubbles. The water may either be inside the magma or groundwater mixed into the magma as it rises to the surface. </li></ul>
  18. 18. Hawaiian style eruptions <ul><li>Generally fairly gentle as the magma is very fluid and allows the bubbles to pass through without causing violent explosions. </li></ul>
  19. 19. Hawaiian Fire Fountain
  20. 20. Reticulite
  21. 21. Reticulite––lapilli
  22. 22. Reticulite Bomb
  23. 23. Pele’s Hair
  24. 24. Cinders
  25. 25. Cinder lapilli at Pu‘u Puai
  26. 26. Pele’s Tears––Lava droplets
  27. 27. Low Fountain and Tephra Cone––Pu‘u ‘Ō‘ō
  28. 28. Dome Fountain
  29. 30. Spatter Bombs in Flight
  30. 31. Spatter Deposits
  31. 33. Pele’s Hair From Skylight
  32. 34. Strombolian style eruptions <ul><li>These eruptions are marked by bursts of gas that are more explosive than Hawaiian eruptions due to the greater viscosity of the magmas that keeps gas from escaping easily. </li></ul><ul><li>Builds cinder cones like those seen on Mauna Kea, Hualālai, Haleakala, etc. </li></ul>
  33. 39. Cinder Cone Kohala Mountains Cinders and Bombs
  34. 40. Volcanic Bomb––Mauna Kea
  35. 41. Small Volcanic Bombs––really lapilli!!
  36. 42. Pumice Bomb at Pu‘u Waa Waa
  37. 43. <ul><li>Explosive Hawaiian eruptions that make ash are all driven by groundwater or seawater mixing with the magma. </li></ul>
  38. 44. Ballistic Spatter at Ocean Entry
  39. 46. Large Lithc Block in Spatter Field at Ocean Entry––Related to Collapse of Bench and Large Steam Explosion
  40. 47. Spatter and Steam Cloud
  41. 48. Ballistic Spatter and Steam Cloud
  42. 49. Limu o Pele bubble bursting
  43. 50. Limu o Pele
  44. 51. Limu O Pele
  45. 52. Coarse Littoral Ash from Steam Plume
  46. 54. Footprints in Ash
  47. 57. Accretionary Lapilli
  48. 58. Accretionary Lapilli in Keanakako`i Ash near Footprints
  49. 59. Diamond Head is made of ash and accretionary lapilli.
  50. 60. Koko Head
  51. 79. Pumice
  52. 80. Volcanic Ash––Electron Microscope Photo