Nothing is boring in NZ, even the geology is extraordinary!

The mostly submerged New Zealand continent, Zealandia, sits uneasily astride two moving segments of the planet’s surface – the Pacific and Australian plates. In the North Island, the boundary between the plates lies off the East Coast along a depression, the Hikurangi Trough, at the edge of the continental shelf. In the Marlborough region, the boundary cuts diagonally across the South Island to the West Coast. It then continues south-westward along the great Alpine Fault, and runs back out to sea near Milford Sound.

The two moving plates are colliding at a glancing angle. In the process, the sunken New Zealand continent is crumpling to form the land that now projects above sea level. In the north, ocean floor at the surface of the Pacific Plate to the east plunges beneath the continental shelf off the eastern North Island. As it does so, it pushes up the overlying rocks and sediments, creating the hilly terrain of the eastern North Island. In the South Island, the two plates are directly colliding along the Alpine Fault. This causes a much greater uplift, forming the Southern Alps.

At the same time, the country is being wrenched apart. Along the Alpine Fault in the South Island, the West Coast region west of the plate boundary is moving north-east at 2–3 metres per century, relative to the Southern Alps on the eastern side. As this movement continues in the future, the South Island will become more elongated