Hole view into volcano's past

Scientists will drill a deep hole in the Auckland Domain today to find out more about the eruptive history of the city's volcanoes.

The domain covers a volcano which, at about 150,000 years old, is thought to be one of the oldest of the 48 in the Auckland field.

The 30m-deep hole drilled in a sports field will yield a core sample of volcanic ash layers from prehistoric eruptions.

Information from the drill-core will help to reduce uncertainty about the size and timing of prehistoric eruptions, said project co-ordinator Graham Leonard, of GNS Science.

"An important part of understanding the volcanic hazard facing Auckland is to improve our knowledge of past eruptions," said Dr Leonard.

Scientists believe the Auckland volcanic field was formed about 240,000 years ago and has a probable life span of about a million years.

The last volcanic eruption was about 600 years ago and scientists say the next one is likely to come from a new volcano rather than a known one.

Drill-core samples have been taken from other parts of the volcanic field, including Onepoto Domain, on the North Shore and Glover Park, St Heliers.

The 85mm-wide cores are carefully stored at the University of Auckland for analysis.

Dr Leonard said buried sediments beneath the domain would contain layers of ash from other volcanic eruptions further away, such as Mt Taranaki and those in the Central North Island.