Tectonic Uplift

Mountains throughout New Zealand, tell of the continuing tectonic uplift and movement along faults, and through folding.

Faults
Looking north along the Alpine Fault near Franz Josef, with the Southern Alps to the right (east). Image: GNS Science.

Looking north along the Alpine Fault near Franz Josef, with the Southern Alps to the right (east). Image: GNS Science.

Fault lines in New Zealand extend the length of the country and through the sea floor to north, south and east. Over millions of years, displacements (earthquakes) along these faults have drastically changed the appearance of New Zealand, causing its emergence from the sea and creating extensive mountain ranges.

Just two million years ago the sea covered the area now occupied by most of the North Island ranges. Hundreds of earthquakes will have occurred in the intervening time, gradually pushing the mountains up to their present day altitude.

The Alpine Fault is responsible for the uplift of the Southern Alps along its eastern side. It moves at an average rate of up to a centimetre vertically and about three centimetres horizontally per year. (This is an average slip rate - the actual movement happens suddenly during earthquakes every few hundred years.)

Looking east along the Hokunui Hills. The lines of rock beds form the northern limb of the Southland Syncline, with older layers on the left (North) and younger to the right (South). In the foreground these beds are actually overturned slightly. Image: GNS Science.

Looking east along the Hokunui Hills. The lines of rock beds form the northern limb of the Southland Syncline, with older layers on the left (North) and younger to the right (South). In the foreground these beds are actually overturned slightly. Image: GNS Science.

Erosion of the mountain front by glaciers and rivers, and deposition of sediments in other areas, have complicated the topography along the straight line of the fault.

Learn more about how uplift and fault lines affect rivers and how marine terraces provide evidence of uplift around our coastlines.

Folding

When plates and the continents riding on them collide, the accumulated layers of rock can crumple and fold like a tablecloth that is pushed across a table.

Permanent deformation causes the rock layers to bend and curve.