Why Is Auckland Built on Volcanoes?
Auckland is built on volcanoes because the city sits directly over a volcanic field fed by molten rock rising from deep in the Earth's mantle. People settled on it because that same volcanic activity created rich soils, sheltered harbours and defensible hills.
Why is Auckland built on volcanoes?
Auckland sits on top of the Auckland Volcanic Field, a patch of around 53 small volcanoes spread across the city. The field is fed by a source of magma deep in the mantle, well below the crust. When molten rock finds a path to the surface it erupts and builds a new cone, crater or lake. Over roughly the last 200,000 years this has happened again and again across the isthmus, leaving the scatter of hills the city is now built around.
What kind of volcanic field is it?
It is a monogenetic field, which is the key thing to understand. Monogenetic means each volcano erupts only once. Instead of one big mountain erupting over and over like Ruapehu, Auckland gets many small volcanoes, each from a fresh batch of magma taking a new path up. That is why you see dozens of modest cones rather than a single peak.
Why did people settle on a volcanic field?
Because the volcanoes made the land good. The eruptions left deep, fertile soils that were excellent for gardening, which mattered enormously to Māori who terraced and cultivated many of the cones. The hills themselves were natural fortresses, and many maunga became major pā sites with terraces and defensive ditches still visible today. Add two harbours on a narrow isthmus and you have one of the most desirable pieces of land in the country.
Is it safe to live there?
Generally yes, and millions do. The individual cones will not erupt again, since each one is a single-use volcano. The field as a whole is still active, so a future eruption is possible somewhere new, but these are infrequent on a human timescale and closely monitored by GeoNet and Auckland's emergency planners. The risk is real but low, and well understood.
Stand on the field, cone by cone
Volcanic AKL is a field guide to every volcano in the Auckland Volcanic Field, with the geology, history and walking routes for each. Works offline on the maunga.
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