Riverton-Aparima Geology EarthCache
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Riverton-Aparima Geology
The human history of the Riverton-Aparima area goes back several hundred years, but its geological origins go back more than 250 million years to when the supercontinent of Gondwanaland dominated Earth's southern hemisphere. The rocky coast of Western Southland is a great place to look back into deep time and appreciate New Zealand's hidden history.
The topographic map above shows a 40 x 30 km area west of Invercargill. The main towns are Riverton-Aparima (lower right) and Tuatapere (upper left). State Highway 99 is the "Gondwana Trail" between them. The aerial photograph image reveals the forest of the Longwood Range (high point 804 m) surrounded by farmland.
A digital terrain model allows the towns, farms and trees to be "stripped away" and the shape of the solid ground to stand out. Unlike the actively rising, youthful mountains of Fiordland, the Longwoods are a rounded, worn-down range. Geologically young terraces surround the Longwoods on all sides and are especially prominent north of Riverton-Aparima and around the coast. The DTM is a canvas on which geology can be "painted". The four colours on the simple geology map show the type and age of rock that lies under a particular spot:
YELLOW = Holocene-Pleistocene (0-2 million year old) gravels and sand of modern and old beaches and rivers, including Ice Age deposits.
ORANGE = Pliocene-Eocene (2-40 million year old) Waiau Group: soft sandstone, mudstone and limestone. Some fossil wood and shells.
PURPLE = Jurassic-Triassic (150-250 million year old) Median Batholith: hard crystalline granite, diorite and gabbro.
GREEN = Permian (250-280 million year old) Brook Street Terrane: hard green pillow lava, basalt dikes, volcanic breccia, sandstone and mudstone.
Each of these five stones have a local geological history:
To log this Earthcache please do the following:
1. Give the Stones the right name ( 1 - 5 ) ?
2. Why stone No.3 have this form ?
3. Which stone (1 - 5 ) belongs to which geological era?
4. Optional: Take a photo with you or your GPSr together with the Jacobs River Estuary at the background
**You can log this cache right away, you do not need consent from owner of earthcache.
**If the answer is wrong I will email you..
Map images from GNS Science and Land Information New Zealand. Crown Copyright reserved.
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