INVESTIGATING VOLCANIC RECONSTRUCTION USING AKAROA LAVA BENCHES

Volcanic geomorphic signatures and erosional landscape features are key parameters in the reconstruction of volcanic edifices. The highly eroded edifice of the Akaroa Volcanic Complex (AVC), Canterbury, New Zealand provides a unique opportunity to develop volcanic reconstruction methodology. This study looks to topographic surfaces in the AVC, called lava benches, as a potential tool for volcanic reconstruction.

Lava Benches are planar surfaces that represent periods of inactivity and erosion at the end of a phase of effusive volcanism. Lava benches and planezes (sections of preserved volcanic flank bound by drainage pathways), have great potential for marking paleo-topography in reconstruction. Volcanic reconstruction is particularly valuable with highly eroded edifices such as the AVC, as it provides insight into the structural, volcanic, and erosional evolution of the volcano. While lava benches are primarily recognized in Banks Peninsula at this time, the presence of similar features in the Canary Islands (Karátson et al., 2016) suggests these features may be found on eroded volcanic edifices elsewhere, making them ever more relevant.

This study refines previous methodologies, building off of existing understandings of lava benches to gain further insight into the significance of these features. Using DEM data, accompanied by field and GIS assisted recognition and analysis, this study extracts and correlates topographic features for volcanic benches in distinct volcanic sectors of the AVC. Correlated bench surfaces are then transformed into elevation profiles, from which projections toward a vent region are modeled assuming a conical shape for each volcanic sector. Summit estimations using exponential projections range from 2450 to 2900 meters for the upper younger bench surfaces of each volcanic sector. This inconsistency of summit estimations between volcanic sectors supports a multiple eruptive center model for the AVC, suggested by Hampton (2009) and Hobbs (2012), rather than a conical model, as summit estimations would be more consistent with a conical edifice. Variable heights in correlated benches and summit estimations may provide further insight into the relative ages of eruptive stages and age relationships between volcanic sectors, and therefore the constructive history of the AVC.