HR: 14:40h
AN: V43D-04 INVITED     [Abstracts]
TI: Complex Transient Deposition From Historical Sustained Explosive Eruptions
AU: * Houghton, B F
EM: bhought@soest.hawaii.edu
AF: Geology & Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 United States
AU: Bonadonna, C
EM: costanza@cas.usf.edu
AF: Geology, University of South Florida, 4202 Fowler Ave, Tampa, FL 33620 United States
AU: Wilson, C J
EM: cjn.wilson@auckland.ac.nz
AF: Geology, University Of Auckland, Symonds St, Auckland, 1 New Zealand
AU: Sable, J E
EM: jesable@soest.hawaii.edu
AF: Geology & Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822 United States
AU: Fierstein, J
EM: jfierstn@usgs.gov
AF: Volcano Hazards Program, USGS, Middlefield Road, Menlo Park, CA 94025 United States
AU: Hildreth, W
EM: hildreth@usgs.gov
AF: Volcano Hazards Program, USGS, Middlefield Road, Menlo Park, CA 94025 United States
AB: On plots of tephra thickness versus area1/2, steep slopes of Hawaiian and Strombolian deposits distinguish them from subplinian or Plinian pumice sheets. However, several well-described historical pyroclastic deposits have two elements: a cone and an adjacent scoria or pumice sheet or blanket. The relationship between these two architectural elements is an intriguing and unresolved question- what features of the eruptions permit growth of two such disparate elements? Here we examine the geometry for three such eruptions: the subplinian eruption of Ruapehu in 1996, and the Plinian eruptions of Tarawera in 1886 and Novarupta in 1912. Whilst the volumes of tephra apportioned to the two regimes are drastically different during these eruptions, it appears that both co-current (= tephra sheet) and concurrent (cone) transport of pyroclasts can characterize explosive eruptions over a wide range of eruptive intensity. The very proximal deposits are complex in their internal stratigraphy and sedimentation was episodic and fluctuating in intensity and linked to both a Gaussian velocity profile in the jet phase of the eruption plumes and local fluctuations in discharge rate associated with the jet margins
DE: 8428 Explosive volcanism
DE: 8434 Magma migration and fragmentation
DE: 8486 Field relationships (1090, 3690)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005