New Zealand's largest city, sits atop a vast network of lava caves

 

Auckland, New Zealand's largest city, sits atop a vast network of lava caves, with new ones still being discovered. A mapping project is underway to pinpoint their exact locations, providing a blueprint for other volcanic areas globally and potentially averting future disasters.

The caves, formed 70,000 years ago, are a result of Auckland's unique status as a city built on an active volcanic field. With a previously unknown cave being discovered each month, the mapping project aims to earmark and protect these natural wonders, which are not only geologically significant but also hold cultural and practical importance.

Lava caves are empty lava tubes that develop during the transport of fluid molten lava. They can be found in most lava flows but are most common where the lavas are fluid and flow rapidly, making Auckland, Hawaii, and Iceland ideal locations. The longest cave in Auckland stretches up to 290m, while the US boasts a 4km-long cave in Washington's Gifford National Park.

These caves have come to have both practical and cultural significance over the millennia. Native Americans used them as fridges to preserve food, while the Māori, Auckland's indigenous people, consider some caves sacred and use them as burial sites. However, the caves have also been repurposed for clandestine activities, such as a Communist printing press and a mushroom farm.

As development projects spread across the city, the phone rings each time a digger hits a cave. The mapping project aims to manage these discoveries, assessing the size and features of each cave and working with contractors and landowners to preserve them while continuing building projects.

Discovering a cave can be dangerous, with instances of diggers crashing into holes. Increased development and construction across Auckland may lead to more caves being found, potentially affecting construction workers and placing the caves at risk of destruction.

Geologists also worry about the potential for an eruption at any time, with Auckland's volcanic contingency plan designed to prevent a future disaster. Creating a database of Auckland's lava caves will help arm the city against future hazards and potentially provide a blueprint for other similarly volcanic areas around the world.

The mapping project is a collaborative effort between Auckland Council, the University of Auckland, and local Māori heritage practitioners. By working together, they hope to protect these natural wonders, respect their cultural significance, and ensure the city's development is sustainable and safe.