Forecasting the consequences of the failure of the eastern rim of Crater Lake, Mount Ruapehu : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Earth Science at Massey University, Palmerston North, New Zealand
Loading...
Date
2011
DOI
Open Access Location
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Massey University
Rights
The Author
Abstract
A numerical code for simulating dry flows of granular material, Titan2D, was used to
model a range of possible collapse scenarios and resulting debris avalanches from a
possible failure of the eastern crater rim of Mount Ruapehu, New Zealand. The eastern
rim of Crater Lake, Mount Ruapehu consists of a stratigraphic sequence of intercalating
volcaniclastic diamictons, pyroclastics and lavas, some of which are highly
hydrothermally altered. This rim is under outward pressure from Crater Lake and
constitutes one of the steepest parts of the active volcano. Its sudden failure could
involve up to 50 million m³ of rock material, almost certainly generating a debris
avalanche and/or a break-out lahar up to 9 times the size of the March 2007 event. A
failure of hydrothermally altered flank materials on this side of the volcano has already
occurred (c. 4600 yrs Mangaio Fm. (Donoghue & Neall, 2001)). A quantitative hazard
and risk analysis of this scenario has never been undertaken, despite ongoing
hydrothermal alteration and considerable sapping of both the inside and outside of the
rim from explosive eruptions and base surges during the 1995/1996 and 2007
eruptions. New stratigraphic data were integrated with existing high-resolution
topographic information and aerial photography to produce a detailed map of the
eastern rim to highlight the distribution of contrasting stratigraphic sequences and the
distribution of those units with the largest degree of alteration. This information was
used as the first step towards defining the likelihood of different failure volumes and
geometries to be tested in numerical hazard simulations. A quantitative scenariobased
hazard forecast for partial or full collapse of the crater rim and subsequent
events was determined. Simulated data of flow run out, inundation, diversion, velocity
and mass transport were analysed to identify the resulting hazards for the Whangaehu
and Tongariro River catchments. The results of this research suggest that the
Mangatoetoenui, Upper Waikato, Tongariro and Whangaehu River catchments could
be greatly affected by a sudden collapse of the eastern rim and any subsequent lahar
events.
Description
The appendices are on a CD-ROM which is held with the vault copy of the thesis. Appendices include logbook, lab work, Titan2D data and simulation videos.
Keywords
Volcanic hazard analysis, Tongariro National Park, Titan2D, Computer simulation, Volcanic activity