Part 6. Present plate boundary seismic, volcanic and kinematic processes: Magnetics of the Rabaul caldera

Abstract

The Rabaul caldera in East New Britain is a collapse caldera of about 10 km diameter within which some active volcanism remains. Total magnetic field measurements show large anomalies associated with volcanic centres on the East side of the caldera, but only a small one on Vulcan which is on the West side. This correlates with the contrast between the basalts and andesites erupted on the East side, and the dacite pumice and ash of Vulcan. The absence of a large anomaly field on Vulcan may also be due to its structure, being an ash cone lacking in solid lave flows. A programme of repeat measurements on two potentially active craters on the East side has been mounted in order to detect possible anomaly field changes due to thermal changes.