In this orogeny the Southern alps are being formed because the Pacific Plate is being pushed up over the Australian Plate. As the Pacific Plate rises over the Australian Plate it gains altitude, having the effect of giving birth to the Southern Alps.
From 25 to 15 million years ago most of New Zealand was still covered by ocean. Almost all the land that broke the surface of the sea was Torlesse Greywacke. Then the plates started to collide, the crust of New Zealand came under pressure and the Alpine Fault was formed.
Then from 15 million to 5 million years ago the Pacific Plate was rammed up over the Australian Plate along the newly created Alpine Fault. The pressure applied from 25 to 15 million years ago had simply been too much and the crust thickened. This gave birth to the first of the Southern Alps. Also during this period of time, chlorite-grade schist was brought to the surface.
In total about 20 kilometres of uplift has taken place during the Kaikoura Orogeny but most of this has been eroded away.
- The Rise and Fall of the Southern Alps, G. Coates published 2002
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