Kawiti maar: Phreatomagmatic activity in the Kaikohe-Bay of Islands volcanic field, New Zealand

Abstract

Geological and geophysical evidence indicates the existence of at least one maar in the Kaikohe-Bay of Islands volcanic field. The depression at the settlement of Kawiti has a central magnetic anomaly resulting from the vent hidden beneath alluvial sediments. The size and shape of the depression resemble maars from the type locality, Westeifel; in addition, cauliflower bombs and spherical lapilli are present in the ejecta, and these are typical products of phreatomagmatic eruptions. Observations at two other eruption centres suggest that phreatomagmatic eruptions may have occurred elsewhere in this volcanic field.