Cotterill, Adam; (2024) Understanding volcanic processes using satellite remote sensing and multihazard modelling at Manam volcano, Papua New Guinea. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Manam is a frequently active open-vent volcano in Papua New Guinea capable of both explosive and effusive eruptions. Ground-based monitoring is challenging due to steep topography, tropical island conditions and frequent eruptions. Remote sensing observations and probabilistic hazard simulations therefore present valuable resources for monitoring and risk reduction at Manam. This thesis aims to: (a) improve understanding of the volcanological processes governing the observed activity at Manam and open-vent systems generally, and (b) quantify the potential spatial distribution of lava flows and tephra deposition and their impact on human activity. Using satellite remote sensing of thermal and sulphur dioxide emissions and observations of activity, this thesis quantifies Manam’s magma budget and variations in excess degassing through time. From these time series, four distinct phases of volcanic activity are identified between 2018 and 2021. This thesis proposes that eruptive activity at Manam during the study period was driven by the injection and eruption of a volatile-rich recharge magma. In this conceptual model, initial eruptions in August 2018 removed previously degassed magma to re-open the conduit and promote efficient fluxing of volatiles through the shallow magmatic system, accounting for the elevated SO2 fluxes (4.72 kt day-1 ) observed in May-June 2019. The subsequent eruptions may have been triggered by the formation and eventual failure of conduit plugs formed by degassing-driven dehydration crystallization. Probabilistic hazard modelling of tephra deposition and lava flow emplacement have been undertaken using TephraProb and Q-LavHA respectively to constrain the potential exposure of people and assets to these hazards for a range of observed eruption scenarios. Combining simulation results with mapped infrastructure and population data provides insight into the possible impacts of future eruptions at local and regional levels. Consequently, this thesis examines the implications of these results for developing emergency protocols and strategies to improve resilience to Manam’s eruptions.

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