Muriwai, 17 million years before Gannets flew in from Australia.

17 million years ago these layered volcanic sandstones were forming on the ocean floor. Gannets hadn’t been invented yet.

These rocks were raised from the depths as the Australian and Pacific plates slowly collided and ground past each other. Erosion by wind and waves sculpted the layered volcanic sandstones producing Otakamiro Point on Auckland’s west coast. Seventeen million years in the making, it’s a perfect holiday resort for Australian Gannets looking for a mate. Normally they have booked a return flight by May but a few overstayers are living on the edge up there.

During the early Miocene two large lava feeder tubes flowed from fissures around a volcanic island 17 Kilometres west of Muriwai.

Squeezed like toothpaste from a tube, lava oozed into the ocean from the main feeder. Chilled margins formed around the flow as lava at 1000 degrees Celsius hit cold sea water.

At the top of the picture a thin horizontal lave sheet has flowed over pillow shaped lava tubes. Pale coloured, chilled margins surround the pillows top right. Radial joints form inside as the lava cools and contracts.

Lava in the giant feeder cooled slowly. It contracted and a distinctive pattern of radial joints formed.

Cooling with contraction leads to a hexagonal pattern parallel to the cooling surfaces. Jointing runs perpendicular to the cooling surfaces. A set of hexagonal shaped pipes lies on the beach, a chunk from an ancient lava flow.