Southern Alps
The Southern Alps began as sedimentary deposits between 230 and 170 million years ago. The predominantly greywacke formations were uplifted into mountain ranges between 140 and 120 million years ago. From about 26 million years ago, a second continuing period of uplift formed the present-day Southern Alps, driven by the collision of the Pacific tectonic plate with the Australian Plate. The plate boundary is represented by the Alpine Fault which runs slightly west of the main divide of the Southern Alps.