Australia: The Land Where Time Began

A biography of the Australian continent 

Olgas (Kata Tjuta) see Flared Slopes

Kata Tjuta is 32 km from Uluru, a cluster of more than 30 dome-shaped monoliths with deep ravines separating the individuals from each other. They cover an area of 35 km2 and their sheer walls rise abruptly from the flat surface of the surrounding desert. The highest (546 m) is at the western end of the group, much higher than Uluru. Their heights decrease from west to east. The visible part of Kata Tjuta is only the top of a massive block of conglomerate that extends for about 6 km beneath them, and for 10s of kilometres around the visible inselbergs

Sometimes strong winds blow through the group and one area at the north-east end is known as the Valley of the Winds. They have no permanent waterholes but the protected nature of the inner parts of the group allow water to remain for a long time after rain. As a result a variety of animals and plants survive here. A number of plant species not normally found in deserts are large river red gums (Eucalyptus camaldulensis) and species of mosses and ferns. A number of rare plant species occur here, among them a prickly type of grass that grows in clumps (Eriachne scleranthoides), the only other known occurrence being 40 km west at  Mt Currie.

It was previously thought that, like Uluru, Kata Tjuta formed from the same erosion material from the Petermann Ranges, and in the same process, that consolidated then uplifted Uluru. But the slope of the bedding here is only 20o, compared to the 85o of Uluru. The difference in the rock type between Uluru and Kata Tjuta was accounted for by the fact that Kata Tjuta is closer to the Petermann Ranges and so the pebbles and rocks deposited here formed a conglomerate, whereas the finer sand that was deposited further from the source formed the sandstone of Uluru. New evidence has been found that changes this scenario with relation to Kata Tjuta. The rocks forming the Olgas are still called the Mt Currie Conglomerate. The new information that caused the name change is that it is now known that the sediments that formed Uluru were carried by palaeochannels from the south. Those of the Mt Currie Conglomerates were from the west and southwest. 

Like Uluru, Katatjuta was originally one block, but unlike Uluru, it had 2 sets of joints at right angles to one another. By working on these joints erosion was able to carve up the block into the group of blocks that were then rounded, probably mostly by the sand-laden desert winds. The rock of Katatjuta, though a conglomerate, its constituent rocks are just as hard as the Uluru rock, so very erosion-resistant, the main agent of erosion of the blocks being the process of unloading, where buried rocks are uncovered by erosion of the surrounding material allowing the rock to expands as the pressure is released.  Large vertical slabs of rock then flake off leaving sheer vertical faces as is seen in the rocks of Katatjuta.

Aboriginal mythology of Katajtuta

Sources & Further reading 
  1. Penny Van Oosterzee, 1993, The Centre - The Natural history of Australia's Desert Regions, Reed Australia. 
  2. Mary E White, After the Greening, The Browning of Australia, Kangaroo Press, 1994
  3. Mary E White, Running Down, Water in a Changing Land, Kangaroo Press, 2000
Author: M. H. Monroe
Last updated:  04/01/2015


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