# What \*is\* New Zealand? Geologically?

**URL:** <https://boards.straightdope.com/t/what-is-new-zealand-geologically/226184>\
**Category:** Factual Questions\
**Created:** [January 26, 2004, 5:29pm UTC](https://boards.straightdope.com/t/what-is-new-zealand-geologically/226184 "2004-01-26T17:29:48Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\
**Post date:** [January 26, 2004, 5:29pm UTC](https://boards.straightdope.com/t/what-is-new-zealand-geologically/226184/1 "2004-01-26T17:29:48Z")

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Mini-continent, with continental shelves and all? Volcanic upthrust? Part of Australia? Something unique?

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**Author:** ![Tapioca\_Dextrin](https://avatars.discourse-cdn.com/v4/letter/t/3d9bf3/32.png) [@Tapioca\_Dextrin](https://boards.straightdope.com/u/Tapioca_Dextrin)\
**Post date:** [January 26, 2004, 5:42pm UTC](https://boards.straightdope.com/t/what-is-new-zealand-geologically/226184/2 "2004-01-26T17:42:54Z")

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From [here](http://www.gns.cri.nz/what/earthhist/nz_origins/index.html)

> [@](#):
>
> New Zealand originated on the eastern margin of the supercontinent Gondwanaland. Through the process of plate tectonics, the New Zealand landmass separated and drifted during Cretaceous times to become an isolated, partly submerged subcontinent, located between the Tasman Sea and Pacific Ocean.

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**Author:** ![sunfish](https://avatars.discourse-cdn.com/v4/letter/s/96bed5/32.png) [@sunfish](https://boards.straightdope.com/u/sunfish)\
**Post date:** [January 26, 2004, 6:07pm UTC](https://boards.straightdope.com/t/what-is-new-zealand-geologically/226184/3 "2004-01-26T18:07:04Z")

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New Zealand is an island arc, a landmass including a string of volcanoes along the edge of the Australian plate where the Pacific plate is being subducted underneath. The volcanoes have formed because the edge of the Pacific plate that is plunging underneath is melting to form magma pools, and hot magma will eventually rise back toward the surface. The Japanese islands are also part of an island arc, as are the Aleutian islands in Alaska.

New Zealand and Australia both lie within the Australian plate, but the bits that make up the continental parts of the plate have their own distinct geologic histories. This is possible because the plates themselves have been modified repeatedly over time - tearing off pieces and welding new pieces on.

Some useful links:

[Map of the world’s tectonic plates](http://geology.er.usgs.gov/eastern/plates.html)

[Diagram illustrating some of the terms and features associated with plate tectonics](http://pubs.usgs.gov/publications/text/Vigil.html)

[This page has links to some animations of changing continental positions over the past 750 million years.](http://www.ucmp.berkeley.edu/geology/tectonics.html)