Academic literature on the topic 'Mount Egmont'

Thick iron oxide pans are a distinctive feature of some soils in Taranaki, New Zealand, which occur on the ringplain, or on terraces of valleys draining the ringplain of Mount Egmont. The pans tend to form in the boundary area between layers of differing texture within the zone of water table fluctuations. The pans are indurated, brittle, and vesicular, and have a black or reddish brown appearance with a shiny black fracture. They are up to 50 cm thick and form lenticular deposits sometimes several metres across at depths ranging from a few centimetres to about 1 m. Analysis of seven samples of pan gave 34-45% elemental Fe, 3-5% A1 and 4-10% Si, consistent with about 55-70% iron oxides, together with entrapped and adhering soil particles. V and Mo are enriched in the pan samples and probably occur as anionic species strongly adsorbed on the iron oxide surfaces. X-ray powder diffraction, Moessbauer spectroscopy and acid-oxalate dissolution indicate that the dominant iron oxides present are goethite and ferrihydrite. The relative proportion of these two minerals varies widely without any noticeable change in the nature of the pan materials. Microstructures in one sample were examined by scanning electron microscopy. The pans are considered to have formed from the aeration of groundwaters (rich in ferrous ions) moving laterally through the soils. Such groundwaters are formed on Mount Egmont from the reaction of meteoric water, sometimes containing dissolved volcanic carbon dioxide, with ferromagnesian minerals. Positive tests for ferrous ions (using �,�'-dipyridyl as indicator) were obtained from groundwaters presently associated with the pans.

The microprobe-determined glass shard major element chemistry of tephras derived from five North Island, New Zealand volcanoes (Mayor Island, Okataina, Taupo, Tongariro, and Mount Egmont) and younger than ca. 20,000 yr B.P. was subjected to discriminant function analysis. Four separate approaches were adopted to test the match of the tephras with their known sources: (1) an analysis of raw microprobe data; (2) an analysis of normalized data; (3) an analysis of the data transformed by calculating the log10 of oxide scores divided (arbitrarily) by the chlorine content; and (4) a repeat of (3) with multivariate outlier scores, as determined by principal components analysis, deleted. All yielded excellent classification functions (efficiencies of 91–100%), with the eruptives associated with each of the five volcanoes being chemically distinct from one another. In each approach, the first two canonical discriminant functions accounted for >90% of the variation between groups. The removal of multivariate outliers from the data set had only minor effects on the performance of the discriminant function procedures. Separate discriminant function analysis of the relatively alike Taupo and Okataina eruptives gave a greater degree of multivariate separation. The numerical classifications generated should enable unidentified tephras erupted since ca. 20,000 yr B.P. from the five volcanoes to be provisionally matched with their sources.

The aim of this thesis is to examine the resilience and vulnerability of Taranaki communities to volcanic hazards, and to propose a strategy to ensure the safety and longevity of Taranaki residents in the event of an eruption. Mt Taranaki is a dormant volcano that is surrounded by a ring plain populated by over 100,000 people. The volcano has had an average eruptive cycle of 330 years, with the last eruption dated at ~1755 AD. Hazards include ash fall, lahars, debris avalanches and pyroclastic density currents. Inglewood, Stratford and Opunake are the largest population centres located in moderate to high hazard zones, and for this reason were chosen as the study communities. Resilience is defined as the capacity to respond to a hazard event by physically and psychologically recovering, adapting to, or changing to similar or better conditions than those experienced before the event. Vulnerability is defined to be people�s incapacity to cope with a hazardous event as a result of their personal characteristics. A person�s vulnerability and resilience is influenced by demographic variables, socio-cognitive variables and preparedness. Inglewood, Stratford and Opunake adults have good self-efficacy and action-coping use, fair risk perceptions, outcome expectancy and response efficacy, but poor understanding of event timing relative to eruption probability, critical awareness, preparedness and information-seeking intentions and preparedness levels. Preparedness is found to be influenced by residents� intentions to prepare, which in turn are influenced by critical awareness, action-coping and outcome expectancy. Taranaki students have a fair awareness of hazard and knowledge of correct response behaviours to various hazards. Preparedness, in terms of preparedness measures undertaken, emergency plans made and emergency practices in place, is low. Students who have participated in hazard-education programmes have a better knowledge of response behaviours, lower levels of hazard-related fear, and reported higher level of preparedness. Spatial analyses, carried out to determine the geographic distribution of at-risk groups within the study communities, showed that the areas most at-risk tend to be those with the highest population densities. The spatial analysis was not as beneficial as expected, due to small data sets, but did provide some results to be considered as a basis for further research. Effective public education can be achieved when delivered to a set of guidelines, such as providing information regularly through multiple media and sources, ensuring consistent messages, targeting information to at-risk groups and monitoring programme effectiveness. Community capacity building projects decrease aspects of vulnerability and build resilience by working at a local scale and targeting at-risk groups. Psychological preparedness education helps citizens to mentally prepare for an event and should be a component of all projects. The proposed strategy calls for (a) forming partnerships with relevant stakeholders to assist with public education, research, and funding, (b) further research into the characteristics of Taranaki communities and effective public education campaigns, (c) the development and implementation of a public education schedule and projects that build community capacity, and d) long-term planning, periodic revision of programmes and consistent public engagement.

The long-term behaviour of andesitic stratovolcanoes is characterised by a repetition of edifice growth and collapse phases. This cyclic pattern may represent a natural frequency at varying timescales in the growth dynamics of stratovolcanoes, but is often difficult to identify because of long cycle-timescales, coupled with incomplete stratigraphic records. The volcaniclastic ring-plain succession surrounding the 2 518 m Mt. Taranaki, New Zealand, comprises a wide variety of distinctive volcanic mass-flow lithofacies with sedimentary and lithology characteristics that can be related to recurring volcanic cycles over >190 ka. Debrisflow and monolithologic hyperconcentrated-flow deposits record edifice growth phases while polylithologic debris-avalanche and associated cohesive debris-flow units were emplaced by collapse. Major edifice failures at Mt. Taranaki occurred on-average every 10 ka, with five events recognised over the last 30 ka, a time interval for which stratigraphic records are more complete. The unstable nature of Mt. Taranaki mainly results from its weak internal composite structure including abundant saturated pyroclastic deposits and breccia layers, along with its growth on a weakly indurated and tectonically fractured basement of Tertiary mudstones and sandstones. As the edifice repeatedly grew beyond a critical stable height or profile, large-scale collapses were triggered by intrusions preceding magmatic activity, major eruptions, or significant regional tectonic fault movements. Clasts within debris-avalanche deposits were used as a series of windows into the composition of previous successive proto-Mt Taranaki edifices in order to examine magmatic controls on their failure. The diversity of lithologies and their geochemical characteristics are similar throughout the history of the volcano, with the oldest sample suites displaying a slightly broader range of compositions including more primitive rock types. The evolution to a narrower range and higher-silica compositions was accompanied by an increase in K2O. This shows that later melts progressively interacted with underplated amphibolitic material at the base of the crust. These gradual changes imply a long-term stability of the magmatic system. The preservation of similar internal conditions during the volcano’s evolution, hence suggests that external processes were the main driving force behind its cyclic growth and collapse behaviour and resulting sedimentation pattern.