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Radiometric dating volcanic rock

The collision of these plates caused the Pacific plate to subduct underneath the Australian plate which carries the North Island.

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The Latah Formation sediments of Washington and Idaho are interbedded with a number of the Columbia River Basalt Group flows, and outcrop across the region.The zones in New Zealand are defined by trenches in the north and in the south and by the Alpine Fault which connects the two.This plate boundary has shaped the size of New Zealand and also defines its geology.The orogeny deformed the sediments deposited during the earlier sedimentation period differently: the western rocks in open simple folds, whereas the eastern block was much more severely deformed, commonly in a stack of folds with complex faulting. The break-up, Cretacous to Oligocene period (99 to 24 million years ago) This period is characterised by a long period of weathering and erosion of the mountains that were formed during the preceding orogeny, so much so that some places were reduced to so called , that is areas of low relief.About 85 million years ago a rift valley formed to separate the New Zealand region from the rest of Gondwana, resulting in the formation of a new ocean floor by means of and by the Oligocene period (about 35 million years ago) most of the country was submerged.It was the beginning of the area that is now known as New Zealand and was just off the coast of Gondwana.

Some volcanic islands built up after they became extinct, were covered with sands and mud, washed down from the land.

Plutonic intrusions formed granite and in some places diorite.

The exact mountain building details are not known as materials got deformed, eroded or covered by younger material, but it can be presumed that all these activities happened along the former coast of Gondwana, long before New Zealand existed. The New Zealand Geosyncline, Carboniferous to Jurassic period (about 330 to 142 million years ago) During this time enormous thicknesses of sediment accumulated, extending northwest from New Zealand to New Caledonia and south far below the South Island.

The islands forming New Zealand developed as part of a broader ): 1.

The early sedimentation depositional phase, Cambrian to Devonian period (about 545 to 370 million years) This was the period when the earliest major recorded rock formation was taking place, with the oldest rocks being found on the west coast of the South Island.

This has resulted in about 450 km of displacement along the Alpine Fault.