Journal Articles

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Start date: 2021Subject: search.filters.subject.andesite stratovolcano

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    Stratigraphy and lithosedimentological properties of subplinian eruptions from Mt. Taranaki, New Zealand, encompassed by the Ngaere and Pungarehu edifice collapses
    (Taylor and Francis Group, 2025-01-29) Mills S; Procter J; Zernack A; Mead S
    The sudden removal of large portions of a volcanic edifice through collapse can cause depressurisation in the subvolcanic magmatic system, influencing the nature of subsequent eruptions. At Mt. Taranaki, edifice failure has occurred frequently and at different timescales throughout the volcanic history, forming a broad pattern of cyclic collapse and regrowth. About 20–30,000 years ago, Mt. Taranaki experienced two such cycles in short succession, emplacing the 27.3 ka Ngaere and the 24.8 ka Pungarehu debris-avalanche deposits, which were preceded and followed by a sequence of twenty-eight closely spaced tephra deposits known as the Poto and Paetahi Formations. Here, we reconstruct the tephrastratigraphic framework of the Poto and Paetahi Formations, revealing a minimum total eruptive volume of 3 km3. While eruptions directly following edifice failure were larger compared to those prior to collapse, this 4,000-year long eruptive period was characterised by consistently large subplinian eruptions. In contrast, large explosive events within the Holocene sequence are less frequent, with more multi-phase periods of effusive and explosive activity recorded. Our new data highlights the need to include longer-term eruptive records in volcanic hazard modelling since the most recent volcanic history might not cover the full nature of volcanic processes occurring at long-lived stratovolcanoes.
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    The geological history and hazards of a long-lived stratovolcano, Mt. Taranaki, New Zealand
    (Taylor and Francis Group on behalf of the Royal Society of New Zealand, 2021-03-17) Cronin SJ; Zernack AV; Ukstins IA; Turner MB; Torres-Orozco R; Stewart RB; Smith IEM; Procter JN; Price R; Platz T; Petterson M; Neall VE; McDonald GS; Lerner GA; Damaschcke M; Bebbington MS
    Mt. Taranaki is an andesitic stratovolcano in the western North Island of New Zealand. Its magmas show slab-dehydration signatures and over the last 200 kyr they show gradually increasing incompatible element concentrations. Source basaltic melts from the upper mantle lithosphere pond at the base of the crust (∼25 km), interacting with other stalled melts rich in amphibole. Evolved hydrous magmas rise and pause in the mid crust (14–6 km), before taking separate pathways to eruption. Over 228 tephras erupted over the last 30 kyr display a 1000–1500 yr-periodic cycle with a five-fold variation in eruption frequency. Magmatic supply and/or tectonic regime could control this rate-variability. The volcano has collapsed and re-grown 16 times, producing large (2 to >7.5 km3) debris avalanches. Magma intrusion along N-S striking faults below the edifice are the most likely trigger for its failure. The largest Mt. Taranaki Plinian eruption columns reach ∼27 km high, dispersing 0.1 to 0.6 km3 falls throughout the North Island. Smaller explosive eruptions, or dome-growth and collapse episodes were more frequent. Block-and-ash flows reached up to 13 km from the vent, while the largest pumice pyroclastic density currents travelled >23 km. Mt. Taranaki last erupted in AD1790 and the present annual probability of eruption is 1–1.3%.