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Lake layers clear waters on Rangitoto volcanic longevity

Microscopic tephra layers (crypto-tephra) in lake sediments have revealed the longevity of Auckland’s largest and youngest volcano – Rangitoto.

Normally, the life-span of small volcanoes in basaltic fields – commonly considered “monogenetic” – can be difficult to assess because of a lack of datable materials.

Previous studies have suggested construction of Rangitoto over a relatively short period.

However, the tephra record indicates intermittent activity at Rangitoto for a much longer period.

Rangitoto represents about half the magma erupted in the Auckland Volcanic Field (AVF) history.

This shows that the AVF has undergone a huge move to prolonged and voluminous central-vent volcanism in its recent history, demonstrating the difficulty in determining time-erupted volume relationships. AVF hazard-risk modelling needs to be revisited in light of the new Rangitoto chronology.

Attachments

Longevity of a small shield volcano revealed by crypto-tephra studies (Rangitoto volcano, New Zealand): Change in eruptive behaviour of a basaltic field. Cover
Longevity of a small shield volcano revealed by crypto-tephra studies (Rangitoto volcano, New Zealand): Change in eruptive behaviour of a basaltic field.

Journal of Volcanology and Geothermal Research

Publication Date: 01/05/2013