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

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

5. 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.

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

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

9. ~2 cm Typical high-fountaining pyroclasts: reticulite, scoria, Pele’s tears, and Pele’s hair

10. Crude layering in a typical high-fountaining deposit

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

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

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

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

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

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

17. Spatter is fluid when it lands ~20 cm

18. ~2 m-wide spatter cone, flank of Pu‘u ‘O‘o scoria cone behind - -

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

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

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

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

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

25. (Kapoho, 1960) HYDROMAGMATIC ERUPTIONS

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

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

28. 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

30. 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

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

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

33. Accretionary lapilli: liquid water in the eruption cloud

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

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

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

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

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

39. PAU