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vicked.vicky
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Joined: 03 May 2008
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 Posted: Oct 29, 2008 Topic Views : 1054 Post subject: Karlu Karlu: The Devils Marbles of Granite Australia |
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Karlu Karlu also known as the Devils Marbles Conservation Reserve is located south of Tennant Creek area of Northern Territory in Australia. The area is located near Wauchope, 114km south of Tennant Creek, in the Northern Territory. It contains formations of naturally rounded and oval boulders called Karlu Karlu by the local Aborigines. The boulders are located in a traditional Aboriginal sacred site and are important to the local Aboriginal people.
The Kaytetye people believe that the boulders are the eggs of the rainbow serpent. Over time, the ceremonies and stories related to the Devils Marbles have largely been lost, but the site is still very important to the tribe and may be considered to be among the oldest religious sites in the world. The Reserve is accessible (by short pathways) all year round and has a network of pathways with information boards and a basic camping area.
The Devil's Marbles are made of granite, which surfaces like a little geological island in the desert, surrounded by incredible amounts of sandstone. The granite is thought to be formed about 1.7 billion years ago as a result of the hardening of magma within the earth's crust. Thick layers of sandstone on top of it put a lot of pressure on this granite. After the folding of the earth's crust, which lead to the lifting of the granite, and the erosion of the sandstone the granite came to surface. The pressure was gone which caused the granite to be able to expand; cracks formed, and it fell apart in big, square blocks.
The second phase of the formation of the Marbles started when these blocks got exposed to water. The surface of the blocks began to decay under the influence of the water, and a layer of loose material surrounded the individual blocks. When they came to the surface completely, this layer was flushed away by water and blown away by wind. The next phase of decay had started now.
The roundening of the granite blocks is a result of both chemical and mechanical weathering. Firstly, exfoliation plays a part. Chemical processes cause the surface of the blocks to expand and/or shrink. Thin layers of rock come off the boulder. This rounds the granite block, because the chemical processes have more effect on areas with edges. These processes cause the rock to look like it is made of layers like an onion. In effect, only the outer few centimeters are affected by chemical weathering. This process is called spheroidal weathering. Secondly, the boulders are suffering from solarisation. Because the temperature differences between day and night are so great, the rocks expand and shrink a little bit every 24 hours. This causes some rocks to crack, sometimes even splitting them in half.
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