Age, distance, and geochemical evolution within a monogenetic volcanic field: Analyzing patterns in the Auckland Volcanic Field eruption sequence

Abstract

[1] The Auckland Volcanic Field (AVF) is a young active monogenetic basaltic field, which contains $50 volcanoes scattered across the Auckland metropolitan area. Understanding the temporal, spatial, and chemical evolution of the AVF during the last c.a. 250 ka is crucial in order to forecast a future eruption. Recent studies have provided new age constraints and potential temporal sequences of the past eruptions within the AVF. We use this information to study how the spatial distribution of the volcanic centers evolves with time, and how the chemical composition of the erupted magmas evolves with time and space. We seek to develop a methodology which compares successive eruptions to describe the link between geochemical and spatiotemporal evolution of volcanic centers within a monogenetic volcanic field. This methodology is tested with the present day data of the AVF. The Poisson nearest neighbor analysis shows that the spatial behavior of the field has been constant overtime, with the spatial distribution of the volcanic centers fitting the Poisson model within the significance levels. The results of the meta-analysis show the existence of correlations between the chemical composition of the erupted magmas and distance, volume, and time. The apparent randomness of the spatiotemporal evolution of the volcanic centers observed at the surface is probably influenced by the activity of the source. The methodology developed in this study can be used to identify possible relationships between composition trends and volume, time and/or distance to the behavior of the source, for successive eruptions of the AVF.

A combined field and numerical approach to understanding dilute pyroclastic density current dynamics and hazard potential: Auckland Volcanic Field, New Zealand

“…Volcanic products, which range in age from 250 to 0.6 ka (Shane and Sandiford, 2003;Brothers and Golson, 1959;Lindsay et al, 2010), cover an area of 360 km 2 and consist of ~50 eruptive centers, 39 of which produced explosive phreatomagmatic eruptions (Searle, 1964;Kermode, 1992). Allan and Smith (1994) estimated that ~71% of past AVF eruptions have had a base surge-producing phreatomagmatic phase.…”

“…The relatively high sea level and abundant aquifers in the Miocene sediments beneath the AVF indicate a high probability that the initial phase of future AVF eruptions will be phreatomagmatic in nature (Lindsay et al, 2010;Sandri et al, 2012). The probability of a future phreatomagmatic eruption, combined with the uncertainty of vent location and size of a future eruption(s), has motivated focused research on past and possible future phreatomagmatic eruptions and base surges in the AVF (e.g., Searle, 1964;Kermode, 1992;Smith and Allen, 1993;Allen and Smith, 1994;Magill and Blong, 2005;Lindsay et al, 2010;Sandri et al, 2012;Bebbington and Cronin, 2011).…”

Evaluating the impacts of volcanic eruptions using RiskScape

“…For crosshazard comparative purposes, the recurrence rate is between 500 and 20,000 years (Molloy et al, 2009). A further challenge is that there are no definitive spatial or volumetric trend for the location or size of AVF eruptions (e.g., Bebbington and Cronin, 2011;Le Corvec et al, 2013;Bebbington, 2015).…”

Sensitivity to volcanic field boundary

“…This approach was expanded by Bebbington (2013) to include an outer ellipse with an exponentially decaying intensity. Rectangular bounds were employed by Lindsay et al (2010), and a convex hull with a~1 km buffer zone was employed for exploratory analyses by Le Corvec et al (2013a).…”

“…This value comes from Runge et al (2014) and represents the > 95 % upper limit of dyke length from posterior distributions adapted to Harrat Rahat, with initial prior distributions taken from an eroded analogue volcanic field (San Rafael, Utah, Delaney and Gartner 1997), and expert elicitation. Although adapted specifically for Harrat Rahat, the same distance was applied to the Auckland Volcanic Field, while Le Corvec et al (2013a) used~1 km. In this work, Harrat Rahat was used to illustrate the sensitivity of spatial intensity results to the inclusion of a buffer.…”