Rangitata Orogeny
Encyclopedia
The Rangitata Orogeny was a long period of uplift and collision in New Zealand
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200 million years ago, sedimentary strata was being pushed along the sea floor as the result of seafloor spreading
. The moving rocks were being pushed towards a gap in the crust or subduction zone. However, when the rocks reached this zone, the wet sediments were too buoyant to follow the heavier ones through the subduction zone. Instead of this the strata was scraped off the crust and squeezed against sediments in the volcanic sea to the west. This collision lasted for 50 million years.
However, the wet sediments could not just keep piling up. After 50 million years, there was simply to much rock and a 'log jam' in the process was formed. The rocks were squeezed together as they broke and crumpled up. As the compression intensified, the strata was slowly pushed up, creating new land.
The collision was also causing a great thickening of the crust, pushing the rocks down into the top of the mantle. The high pressures and temperatures of this occurrence metamorphosed the lower rocks into the Haast Schists
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New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
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200 million years ago, sedimentary strata was being pushed along the sea floor as the result of seafloor spreading
Seafloor spreading
Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics....
. The moving rocks were being pushed towards a gap in the crust or subduction zone. However, when the rocks reached this zone, the wet sediments were too buoyant to follow the heavier ones through the subduction zone. Instead of this the strata was scraped off the crust and squeezed against sediments in the volcanic sea to the west. This collision lasted for 50 million years.
However, the wet sediments could not just keep piling up. After 50 million years, there was simply to much rock and a 'log jam' in the process was formed. The rocks were squeezed together as they broke and crumpled up. As the compression intensified, the strata was slowly pushed up, creating new land.
The collision was also causing a great thickening of the crust, pushing the rocks down into the top of the mantle. The high pressures and temperatures of this occurrence metamorphosed the lower rocks into the Haast Schists
Haast Schist
The Haast Schist is a New Zealand schist that is found on the eastern side of the Alpine Fault. Metamorphic grade progresses from greenschist through biotite schist to garnet schist. Myrmekitic textures occur within oligoclase within the garnet zone....
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