New Zealand Journal of Geology & Geophysics abstracts
A review of break-out floods from volcanogenic lakes in New Zealand
V. Manville1,*
K. A. Hodgson2
I. A. Nairn3,1
1GNS Science
Wairakei Research Centre
Private Bag 2000
Taupo, New Zealand
2Western Heights High School
Old Quarry Road
Rotorua, New Zealand
345 Summit Road
RD5, Rotorua, New Zealand
*Corresponding author: v.manville@gns.cri.nz
Abstract New Zealand hosts numerous lakes in its
active volcanic areas. These water bodies are developed in calderas,
volcano-tectonic collapse structures, explosion craters, and valleys
dammed by lava, pyroclastic, or laharic flows. They range in scale and
elevation from small shallow ponds a few metres above sea level in
Auckland, through volcano-tectonic collapse structures such as the
Rotorua and Taupo calderas that hold many cubic kilometres of water at
a height of a few hundred metres, to the summit Crater Lake of Mt
Ruapehu, which contains c. 9 × 106 m3
of hot acidic water at an altitude of 2530 m. The combination of active
volcanism and New Zealand's temperate climate means that new lakes can
form or old ones overfill rapidly following activity at any volcanic
centre.
Lakes in volcanic environments are often relatively
short-lived features compared with those in tectonic settings, being
prone to rapid formation and/or modification/destruction by both
primary volcanic processes and the secondary effects of post-eruptive
landscape re-adjustment. In addition to primary eruption-related
volcano-hydrologic hazards, significant delayed hazards can also result
from partial to total failure of impounding barriers of volcanic
material. For example, New Zealand's worst volcanic disaster, the 1953
Tangiwai lahar, which resulted in 151 deaths, was caused by partial
failure of the rim of Mt Ruapehu's Crater Lake 8 yr after the 1945
eruption had ended. Most recently, post-1996 refilling of the lake
behind a barrier of unconsolidated tephra laid down during the 1995/96
eruption sequence culminated in breaching and failure of the dam on 18
March 2007, resulting in the release of 1.3 × 106 m3
of water and generation of the largest historic lahar at the volcano.
Historical reports and
geomorphic/sedimentologic studies demonstrate that many of New
Zealand's volcanogenic lakes have been the source of large-magnitude
floods, some of which have caused major re-organisation of regional
drainage networks. Post-eruption failures of the topographic rim of the
Taupo caldera have produced catastrophic releases of up to 60 km3
of water, whereas intracaldera lakes hosted within the Okataina and
Rotorua Volcanic Centres have also been the source of repeated floods.
At least four events have been identified from Lake Tarawera (Okataina
Volcanic Centre) in response to volcanogenic modification of the lake
basin and catchment, most recently following the AD 1886 Tarawera
eruption. Paleohydraulic reconstructions of dam-breach hydrographs and
downstream flood discharge rank some New Zealand caldera lake
break-outs as amongst the largest known Holocene floods on Earth.
Keywords volcano-hydrologic hazards; caldera and
crater lakes; paleohydrology; floods; lahars; natural hazards
G06017; Online publication date 14 May 2007; Received 26 June 2006;
accepted 2 May 2007
New Zealand Journal of Geology & Geophysics, 2007, Vol. 50:
131—150
0028—8306/07/5002—0131 © The Royal Society of New Zealand 2007
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