Qwerty

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  • Topic: Plate tectonics, Convergent boundary, Subduction
  • Pages : 7 (2618 words )
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  • Published : February 23, 2013
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Geology internal
Surface feature: Kiwi point quarry rock face
Johnsonville
Shops
Reference:
http://maps.google.co.nz/
Ngauranga gorge

Kiwi point quarry

Reference: http://maps.google.co.nz/
Exposed quarry rock face from the road in Ngauranga gorge (picture 1). Take note that most of the other photos after this are taken of the rocks behind the trees and below it.

Outline of kiwi point quarry

Roughly
4m
The picture to the left is a picture of the bottom of the rock face in the quarry and as you can see the rocks are quite grey in color. They have lots of cracks and jagged edges due to rocks breaking away caused by human mining and weathering. The rock face has also got black lines running through it. In picture one of the entire rock face you can see that the entire rock face is about 30m tall and is slopped backwards. The rock face also faces to the south. (Picture 2) looking straight on at a lower part of the rock face. –-–

In picture 3 of the rock face you can see that as you look higher up the rocks get browner. This is evidence of weathering and oxidization in the rocks making them weaker at the top. In kiwi point quarry 350 000 tones of greywacke are shipped out every year which means that the rocks in the pictures are mainly greywacke, which is a hard sedimentary sandstone and is grey in color and as you can see all the rocks are grey, apart from the brown weathered ones, which are just weathered greywacke.

A picture looking up the rock face.
(Picture 3)

At the bottom of the rock face there were also piles of brown colored rocks, this is evidence of weathering and erosion. Some parts of the rock face are flat as you can see in picture 2, but a majority is all jagged from broken of rocks. The black lines running through the rocks in picture 2 also resemble layering in the greywacke and as they are not straight they also show folding in the rocks. The black lines in between the greywacke I have identified as shale which is a soft rock made of clay and mud. Shale is a sedimentary rock that is weak and brittle. Shale can be a variety of colors but is black in Kiwi Point Quarry which means it is made of more than one percent carbon from organic matter. I also thought the black lines could have been argillite as it makes up some of the basement rock in Wellington and is very similar to shale. However argillite is not fissile like shale, fissile meaning the rocks break easily. The black rocks in the quarry did in fact break apart easily making me very confident it is shale. The rock face also has 4 or 5 ledges going all the way up but they are most likely man made due to the fact that it is a quarry.

Internal processes

1. Sediments forming new rock millions of years ago
2. Lifting up of the rocks due to tectonic plate movement and faulting

The greywacke in kiwi point quarry would have started out somewhere. That somewhere is millions of years ago on a large continent called Gondwanaland. In Gondwanaland there would have been rocks already formed, this could have been done by lava cooling and turning into solid rock called igneous rock, or movement of tectonic plates pushing up sedimentary rock. Sedimentary rock is rock that is formed from the sediments of weathered down and eroded rocks from other bigger rocks. The bigger rocks these sediments come from are called parent rocks. Some examples of sediments and parent rocks are quartz making sand and feldspar making clay. As greywacke is sandstone it is made of sand and would have been formed from the sediments of quartz. Greywacke is also a little bit of a metamorphic rock. A metamorphic rock is a sedimentary or igneous rock that gets heated up under the Earth’s crust. This can make the rock melt and change into another form or make the crystals inside them change. Greywacke is a little bit metamorphic because it goes through a little bit of heat and pressure but not enough to completely change the greywacke....
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