Orogeny Orogen" resulted from these events and various others that are part of its peculiar orogenic cycle. In summary, an orogeny is an episode of deformation, metamorphism and magmatism at convergent plate margins, during which many geological processes play a role at convergent plate margins. Every orogeny has its own orogenic cycle, but composite orogenesis is common at convergent plate margins. Erosion represents a subsequent phase of the orogenic cycle. Erosion inevitably removes much of the mountains, exposing the core or "mountain roots" (metamorphic rocks brought to the surface from a depth of several kilometres). Isostatic movements may help such exhumation
Kaikoura Orogeny Kaikoura Orogeny The Kaikoura Orogeny is a New Zealand orogeny that has given birth to the Southern Alps. It began 25 million years ago along the Alpine Fault. In this orogeny, the Southern Alps are being formed because the Pacific Plate is colliding with the Australian Plate, with a predominant oblique dextral motion, but a minor component of thrust faulting. As the plates collide, the crust thickens, with deformation and associated uplift due to isostacy occurring primarily within the Pacific Plate. From 25 to 15 million years ago most of New Zealand was still covered by ocean. Almost all the