New Zealand Journal of Geology and Geophysics abstracts
Distribution, stratigraphy, and history of proximal deposits from the c. AD
1305 Kaharoa eruptive episode at Tarawera Volcano, New Zealand
I. A. NAIRN1
S. SELF2
J. W. COLE3
G. S. LEONARD3
C. SCUTTER2
1RD 5, Rotorua
New Zealand
2Department of Geology and Geophysics
University of Hawaii at Manoa
2525 Correa Road
Honolulu, Hawaii 6822, USA
3Department of Geological Sciences
University of Canterbury
Private Bag 4800
Christchurch, New Zealand
Abstract The c. AD 1305 Kaharoa eruptive episode consisted of
a complex sequence of basalt-triggered high-silica rhyolite eruptions from at
least seven vents along an 8 km linear zone across Tarawera Volcano.
Initial plinian eruptions from a summit vent spread Kaharoa Tephra southeast
across the North Island, accompanied by phreatomagmatic explosions and
pyroclastic density currents from vents opened on the northern flanks of the
volcano. The early plinian phase was ended by extrusion of Crater Dome in the
summit vent, with explosive activity migrating to two adjacent vents (Tarawera
and Ruawahia) to the southwest and northeast. Renewed plinian eruptions,
apparently from the northern vents, produced tephra falls dispersed
northeast-northwest from the volcano. Extrusion of the three summit lava domes
was accompanied by voluminous block-and-ash flows generated by collapse of the
growing Ruawahia and Wahanga Domes, forming large fans to north, southeast, and
northwest of the volcano.
Calculation of Kaharoa lava volumes and comparisons with the extrusion rates
of observed dome-building eruptions suggest a duration of c. 4 yr for the c. 4
km3 Kaharoa eruptive episode. This estimate, of years rather than
days or weeks, is significant for planning an effective response to a future
similar rhyolite episode in New Zealand.
Keywords stratigraphy; Tarawera Volcano; high-silica
rhyolite; multiple vents; plinian eruptions; lava extrusion; domes;
block-and-ash flows; duration
New Zealand Journal of Geology & Geophysics, 2001, Vol 44: 467-484
0028-8306/01/4403-0467 $7.00/0 (c) The Royal Society of New Zealand
2001
PDF file of entire paper: medium quality (6607K); (scanned from paper original: notes about this process)
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