50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...

U-Th-Ra disequilibria data. In particular, it raises
questions about the usefulness of geochronological
interpretations of these data for andesitic volcanoes.
The 1995 – 1996 eruptions of Ruapehu were the
largest and best sampled events since the dome –
forming eruptions of 1945. Nonetheless, the
eruptions were small in global terms (< 0.02 km 3 )
and entirely pyroclastic. Collectively, samples from
the eruptions over the past 60 years display a
spectrum of chemical compositions extending from
andesite to dacite and covering much of the range
shown by the prehistoric record, extending back
150 ka. The temporal variations in isotopic and
trace element variation for andesites and dacites
erupted between 1945 and 1996 are systematic and,
in comparison with prehistoric eruptives, they
provide the basis of a model for predicting future
eruption patterns. The model we have developed
for the Ruapehu magmatic plumbing system could
also be used to design seismic experiments that
might be able to image magma storages beneath the
volcano, thereby providing a more precise basis for
predicting future eruptions.
ORAL
FORECASTING HAZARDS FROM MOUNT
TARANAKI USING TITAN2D
Jon Procter 1 , Shane Cronin 1 ,Abani Patra 2 ,
Keith Dalbey 2 , Mike Sheridan 2
&ThomasPlatz 1 ,
1 Institute of Natural Resources, Massey University,
Palmerston Nth, New Zealand
2 GMFG, State University of New York at Buffalo,
New York, USA
(j.n.procter*massey.ac.nz)
Over the last c. 800 years at Mt Taranaki at least
nine distinct eruption episodes occurred, all of
which involved lava dome production and collapse.
Each episode produced several Block-and-Ash
Flows (BAFs) that were directed north-westward
out of a breached crater wall. The latest domecollapse
in AD 1755 produced a deposit that
covered an area of approximately 2.06x10 6 m 2 and
reached up to 9.6 km from source. Future activity
of this type could have a devastating effect on the
Taranaki Region’s communities, infrastructure and
economy. For hazard planning purposes, a
Volcanic Hazard map of Taranaki was created in
1996, with relative hazard zones relating to the
frequency with which areas were inundated by
volcanic flows in the past, with little consideration
of present-day topography. If a similar sequence of
events occurred today, what effect would current
topography have on flow distribution?
Additionally, would modelled flow inundation
areas be similar to the mapped inundation zones
based on past activity? A numerical geo mass-flow
modelling approach is being used to answer these
questions and to try constructing more-dynamic
hazard maps that can take current topography into
account. The Titan2D program (developed by the
GMFG at SUNY Buffalo) is a “shallow water”,
continuum solution-based, granular-flow model.
The program is adapted by the user for various flow
mechanical properties by changing values for
internal and basal friction as well as the dimensions
of the initial pile. Before this model can be applied
to Taranaki BAFs, we must evaluate the input
parameters. For this we use the AD 1755 casescenario,
since initial collapse volume can be well
constrained to the partially preserved summit dome.
Internal and basal friction angles were evaluated
through an iterative approach by broadly comparing
modelled flow inundations with mapped AD 1755
BAF deposit boundaries (especially run-out). A
range of possible input parameters were determined
to produce a suite of potentially inundated areas
under present-day terrain. This suite of around 10
forecasts from a uniformly distributed range was
then analysed statistically to determine an overall
map displaying relative probabilities of inundation
by a future event of the same magnitude as AD
1755. Using this constrained the range of input
parameters, future hazard forecasts for this scale
and type of event can be undertaken using the
present summit configuration, and altered to
include any changes to topography in the future.
This type of approach may also be adapted to
developing appropriate models for other types and
scales of mass flows possible on Mt Taranaki.
Using this approach with outputs representing
differing probabilities for each event modelled what
methods can be applied to effectively and
efficiently display the hazard and associated risk.
ORAL
PROGRESS REPORT: PALEOMAGNETIC
ANALYSES OF KASTEN CORES FROM THE
WAIPAOA BASIN, NEW ZEALAND
A. Quinn,J.Robbins&G.Wilson
Geology Department, University of Otago, PO Box
56, Dunedin.
(quial125*student.otago.ac.nz)
U-channel samples were collected from several
kasten cores in January 2005 from a research cruise
(KM0502) as part of the Margins Source to Sink
research programme in the Waipaoa Basin, New
Zealand
(http://www.margins.wustl.edu/S2S/S2S.html).
Magnetic measurements of NRM intensity and
direction, magnetic susceptibility (�) and
treatments of AF demagnetisation, ARM and IRM
have been performed. The results from these
measurements are being used in studies to
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