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

ERUPTION STYLES AND VENT FORMS ERUPTION STYLES AND VENT FORMS

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

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

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

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

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

Crude layering in a typical high-fountaining deposit Crude layering in a typical high-fountaining deposit

Pele’s hair - produced in high fountains and skylight Pele’s hair - produced in high fountains and skylight

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

Crude bedding and large bombs in a quarried scoria c ~2 m Crude bedding and large bombs in a quarried scoria c ~2 m

Cow dung bomb, Kilauea Iki (1959) pyroclastic depos Cow dung bomb, Kilauea Iki (1959) pyroclastic depos

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

low fountaining, spatter cones, and spatter rampart (from Volcanoes in the Sea) low fountaining, spatter cones, and spatter rampart (from Volcanoes in the Sea)

Spatter is fluid when it lands ~20 cm Spatter is fluid when it lands ~20 cm

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

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

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

Mauna Iki satellitic shield, Kilauea SW rift zone Mauna Iki satellitic shield, Kilauea SW rift zone

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

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

HYDROMAGMATIC ERUPTIONS (Kapoho, 1960) HYDROMAGMATIC ERUPTIONS (Kapoho, 1960)

May 1924 phreatic eruption, Halema‘u view from Volcano House hotel, photo by Tai Sin May 1924 phreatic eruption, Halema‘u view from Volcano House hotel, photo by Tai Sin

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

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

Koko Rift rejuvenation-stag volcanism, Ko‘olau volcano O‘ahu: -most of these eruptions occurred off the Koko Rift rejuvenation-stag 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

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

“surge” deposits, from lateral, turbulent depositio “surge” deposits, from lateral, turbulent depositio

Accretionary lapilli: liquid water in the eruption clou Accretionary lapilli: liquid water in the eruption clou

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

Keanakako‘i hydromagmatic ash, SW of Kilauea calde 1971 lava Keanakako‘i hydromagmatic ash, SW of Kilauea calde 1971 lava

Keanakako‘i hydromagmatic ash, SW of Kilauea calde Keanakako‘i hydromagmatic ash, SW of Kilauea calde

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

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

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