Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

Cronin, Shane J.; Neall, Vincent E.

doi:10.1080/00288306.2001.9514948

Cited by 22 publications

(12 citation statements)

References 29 publications

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“…These implications are important for studies where the morphology of cones is used to establish patterns of relative age relationships in monogenetic volcanic fields (e.g. Hasenaka and Carmichael, 1985;Cronin and Neall, 2001). Our findings suggest that it is the immediate posteruption erosion that is important, and longer-term processes are likely to only exert a very minor influence on the morphology of phreatomagmatic cones and tuff rings.…”

Section: Erosion Styles and Implications For Geomorphic Datingmentioning

confidence: 67%

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Syn- and post-eruptive erosion, gully formation, and morphological evolution of a tephra ring in tropical climate erupted in 1913 in West Ambrym, Vanuatu

Németh

Cronin

2007

Geomorphology

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Syn-and post-eruptive erosion of volcanic cones plays an important role in mass redistribution of tephra over short periods. Descriptions of the early stages of erosion of tephra from monogenetic volcanic cones are rare, particularly those with a wellconstrained timing of events. In spite of this lack of data, cone morphologies and erosion features are commonly used for long-term erosion-rate calculations and relative age determinations in volcanic fields. This paper offers new observations which suggest differing constraints on the timing of erosion of a tephra ring may be operating than those conventionally cited. In 1913 a tephra ring was formed as part of an eruption in west Ambrym Island, Vanuatu and is now exposed along a continuous 2.5 km long coastal section. The ring surrounds an oval shaped depression filled by water. It is composed of a succession of a phreatomagmatic fall and base-surge beds, interbedded with thin scoriaceous lapilli units. Toward the outer edges of the ring, base-surge beds are gradually replaced in the succession by fine ash-dominated debris flows and hyperconcentrated flow deposits. The inter-fingering of phreatomagmatic deposits with syn-volcanic reworked volcaniclastic sediments indicates that an ongoing remobilisation of freshly deposited tephra was already occurring during the eruption. Gullies cut into the un-weathered tephra are up to 4 m deep and commonly have c. 1 m of debris flow deposit fill in their bases. There is no indication of weathering, vegetation fragments or soil development between the gully bases and the basal debris flow fills. Gully walls are steep and superficial fans of collapsed sediment are common. Most gullies are heavily vegetated although some active (ephemeral) channels occur. These observations suggest that the majority of the erosion of such tephra rings in tropical climates takes place directly during eruption and possibly for only a period of days to weeks afterward. After establishment of the gully network, tephra remobilisation is concentrated only within them. Therefore the shape of the erosion-modified volcanic landform is predominantly developed shortly after the eruption ceases. This observation indicates that gully erosion morphology may not necessarily relate to age of such a landform. Different intensities of erosion during eruption (related to water supply or rainfall) are probably the major influence on gully spacing, modal depth and form. Longer-term post-eruption processes that could be indicators of relative age may include internal gully deepening (below basal debris flow fill sediments) and possibly widening and side-slope lowering due to undercutting and side-collapse.

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Section: Erosion Styles and Implications For Geomorphic Datingmentioning

confidence: 67%

“…In spite of the lack of data on the syn-eruptive erosion or initial state of tephra cones or rings, their erosional morphologies are commonly used for relative age dating in volcanic fields (e.g. Cronin and Neall, 2001) and also long-term erosion-rate calculations (Németh and Martin, 1999).…”

Section: Introductionmentioning

confidence: 99%

Syn- and post-eruptive erosion, gully formation, and morphological evolution of a tephra ring in tropical climate erupted in 1913 in West Ambrym, Vanuatu

Németh

Cronin

2007

Geomorphology

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“…Taveuni (437 km 2 ) is a basaltic volcanic island with a northeast-southwest lineament of over 150 Quaternary vents along its 40 km length. At least 2.7 km 2 of magma has been erupted from over 100 events on Taveuni during the Holocene (Cronin & Neall 2001).…”

Section: Exemplars Of Archipelago Geologymentioning

confidence: 99%

The age and origin of the Pacific islands: a geological overview

Neall

Trewick

2008

Phil. Trans. R. Soc. B

295

237

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The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were initially one plate, produced to the east of the original spreading centre before becoming split into three. The islands of the Pacific have originated as: linear chains of volcanic islands on the above plates either by mantle plume or propagating fracture origin, atolls, uplifted coralline reefs, fragments of continental crust, obducted portions of adjoining lithospheric plates and islands resulting from subduction along convergent plate margins. Out of the 11 linear volcanic chains identified, each is briefly described and its history summarized. The geology of 10 exemplar archipelagos ( Japan, Izu-Bonin, Palau, Solomons, Fiji, New Caledonia, New Zealand, Society, Galápagos and Hawaii) is then discussed in detail.

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“…Voluminous lava flows and thick tephra deposits around Ambae suggest that magmatic events have been more intense in the past and have contributed to some extend to flank destabilization. A similarly structured island of the same size, Taveuni, in Fiji has experienced also several flank failure, probably also related to tectonic activity and dyke intrusion along the central rift axis (Cronin and Neall, 2001). Eruptions with higher magnitude that generate large enough surges to induce volume changes and trigger large seiche-like waves in the neighbouring Manaro Lakua, rainfall-remobilization and masse failure in relation to numerous structural lineaments of Ambae are other potentials for lahars.…”

Section: Other Potential Source For Lahar Eventsmentioning

confidence: 99%

Characteristics of the summit lakes of Ambae volcano and their potential for generating lahars

Bani

Join

Cronin

et al. 2009

Nat. Hazards Earth Syst. Sci.

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Abstract. Volcanic eruptions through crater lakes often generate lahars, causing loss of life and property. On Ambae volcano, recent eruptive activities have rather tended to reduce the water volume in the crater lake (Lake Voui), in turn, reducing the chances for outburst floods. Lake Voui occupies a central position in the summit caldera and is well enclosed by the caldera relief. Eruptions with significantly higher magnitude than that of 1995 and 2005 are required for an outburst. A more probable scenario for lahar events is the overflow from Lake Manaro Lakua bounded on the eastern side by the caldera wall. Morphology and bathymetry analysis have been used to identify the weakest point of the caldera rim from which water from Lake Manaro Lakua may overflow to initiate lahars. The 1916 disaster described on south-east Ambae was possibly triggered by such an outburst from Lake Manaro Lakua. Taking into account the current level of Lake Manaro Lakua well below a critical overflow point, and the apparently low potential of Lake Voui eruptions to trigger lahars, the Ambae summit lakes may not be directly responsible for numerous lahar deposits identified around the Island.

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Holocene volcanic geology, volcanic hazard, and risk on Taveuni, Fiji

Abstract: The Holocene volcanic geology of Taveuni has been mapped in order to produce a volcanic hazard and risk assessment for the island.

Cited by 22 publications

References 29 publications

Syn- and post-eruptive erosion, gully formation, and morphological evolution of a tephra ring in tropical climate erupted in 1913 in West Ambrym, Vanuatu

Syn- and post-eruptive erosion, gully formation, and morphological evolution of a tephra ring in tropical climate erupted in 1913 in West Ambrym, Vanuatu

The age and origin of the Pacific islands: a geological overview

Characteristics of the summit lakes of Ambae volcano and their potential for generating lahars

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