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PYROCLASTIC ACTIVITY AND VENT STRUCTURES ON HAWAIIAN VOLCANOES

-. Scott K. Rowland, University of Hawai‘i at Manoa. PYROCLASTIC ACTIVITY AND VENT STRUCTURES ON HAWAIIAN VOLCANOES. ERUPTION STYLES AND VENT FORMS. The intersection of a dike with the Earth’s surface: a curtain of “fire” (actually lava).

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PYROCLASTIC ACTIVITY AND VENT STRUCTURES ON HAWAIIAN VOLCANOES

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  1. - Scott K. Rowland, University of Hawai‘i at Manoa PYROCLASTIC ACTIVITY AND VENT STRUCTURES ON HAWAIIAN VOLCANOES

  2. ERUPTION STYLES AND VENT FORMS

  3. The intersection of a dike with the Earth’s surface: a curtain of “fire” (actually lava) 1971 eruption viewed from the Hawaiian Volcano Observatory, photo by Hawai‘i Volcanoes National Park staff

  4. Expanding gas drives a lava fountain. The highest fountains in Hawai‘i are >500 m Technically, the base of the fountain is where the gas becomes 75% by volume, and this is usually 10s to 100s of meters below the vent rim.

  5. - - Pu‘u ‘O‘o scoria cone (in the early 1990s)

  6. Scoria cones on the lower south flank of Mauna Kea

  7. Typical high-fountaining pyroclasts: reticulite, scoria, Pele’s tears, and Pele’s hair ~2 cm

  8. Crude layering in a typical high-fountaining deposit

  9. Pele’s hair - produced in high fountains and skylights

  10. - - Blanket of scoria downwind from Pu‘u ‘O‘o

  11. Crude bedding and large bombs in a quarried scoria cone ~2 m

  12. - Cow dung bomb, Kilauea Iki (1959) pyroclastic deposit

  13. Large spindle bomb, East Maui Volcano, SW rift zone

  14. low fountaining, spatter cones, and spatter ramparts (from Volcanoes in the Sea)

  15. Spatter is fluid when it lands ~20 cm

  16. - - ~2 m-wide spatter cone, flank of Pu‘u ‘O‘o scoria cone behind

  17. A line of spatter cones forms a spatter rampart photo by P. Mouginis-Mark

  18. Satellitic shields, from eruptions with ~no pyroclastic activity photo by P. Mouginis-Mark

  19. - Mauna Iki satellitic shield, Kilauea SW rift zone

  20. - - - Kupaianaha lava pond and shield, with Pu‘u ‘O‘o scoria cone in the background

  21. - - Kupaianaha lava pond, Kilauea (1986-1992) ~20 m

  22. HYDROMAGMATIC ERUPTIONS (Kapoho, 1960)

  23. May 1924 phreatic eruption, Halema‘uma‘u view from Volcano House hotel, photo by Tai Sing Loo

  24. Eruption of Capelinhos, Azores, 1957. Note the “base surges” spreading laterally from the base of the column. http://volcanology.geol.ucsb.edu/surgecap.gif

  25. Eruption of Taal, Philippines, 1966. Note the “base surges” spreading laterally from the base of the column. http://assets.nydailynews.com/img/2009/02/03/gal_volcano_1965_taal.jpg

  26. Koko Rift rejuvenation-stage volcanism, Ko‘olau volcano, O‘ahu: -most of these eruptions occurred off the shoreline at the time -tuff cones, many nested and/or coalesced, resulted

  27. Molokini Islet, post-shield alkalic series, E. Maui Volcano from Volcanoes in the Sea (Macdonald et al. 1983)

  28. “surge” deposits, from lateral, turbulent deposition

  29. Accretionary lapilli: liquid water in the eruption cloud

  30. If you find footprints, do not do this ! They are fragile.

  31. - - Keanakako‘i hydromagmatic ash, SW of Kilauea caldera 1971 lava

  32. - - Keanakako‘i hydromagmatic ash, SW of Kilauea caldera

  33. - Keanakako‘i tephra exposed in upper SW rift zone fractures photo by P. Mouginis-Mark

  34. ~1790 AD ~1700 AD Age dates by Don Swanson, USGS HVO - Painting of Keoua’s warriors, killed by an explosive eruption. ~1500 AD Did all this happen in a few hundred years? A few years? Diagram from McPhie et al. (1990)

  35. PAU

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