Kata Tjuta tells an astonishing story

From Yulara tourist resort in the middle of Australia the mysterious silhouette of Kata Tjuta, once called The Olgas, looms in the west, rising 546 metres above the flat, sandy horizon. These domed shaped rock outcrops, just 40 km west of Ayers Rock, were once known as the Olgas, but now they have the indigenous name of 'many heads', or Kata Tjuta.

Circle south around the outcrops and see the tilted layers of sediment. These were deposited when water once flowed across the area. We are told that a depression formed in the earth's crust about 900 million years ago, a length of time we cannot imagine. But was it really so long ago? We need to remind ourselves that these dates are not measured facts but based on beliefs about the past. And what we see at Kata Tjuta shows us that these rocks did not form over millions and millions of years.

Surprise. When we arrive at Kata Tjuta and walk between the massive domes, we discover it is a huge heap of boulders. Here I'm sitting by an outcrop pointing to an oblong rock lying almost flat. These boulders indicate the way the water was flowing when they were so rapidly deposited.

All the tourists I met expressed amazement at these rocks. During my visit I spoke to many people and often asked this question: 'How do you think these rocks were deposited? Was it by a little bit of water over a long time, or a huge flow of water over a short time?' Everyone I asked would chuckle and say 'A lot of water, of course!'

Pointing to a medium sized boulder.

Part of the base of one of the domes of Kata Tjuta. Crammed full of rounded rocks, the wall extends for hundreds of metres overhead. The bouldery deposit also extends hundreds of metres under the ground.

In the middle of the picture one unusual boulder stands out. This one is not rounded but angular. And it is huge, about 2 m long and 0.5 m wide. Such massive chunks of rock are by no means rare, and illustrate the power of the water that carried them along and deposited them in place.

Although the Olgas stand so tall above the plain much of the original deposit has been eroded away. Only the spectacular domes are left. We are told that erosion happened slowly over millions of years, but did it really take that long?

If erosion did happen so slowly, where has all the material gone? Those boulders would hardly be carried away by the wind. This is all we find around the base of the rocks.

If erosion had been happening over millions of years we would expect to find the eroded rock material all around. Near the wall we would find it very thick, virtually the same height as the domes. Further away the debris would taper away to nothing in the distance.

But when we inspect the area, all we find is a thin apron of debris around the base. Notice the large boulders scattered on the apron.

I would not want to be around when one of these massive boulders tumbled down, but there are only a few of them on the apron. Close up they are massive, and give a good indication of how well the rock is cemented together. When they fell, they did not smash into pieces but stayed in one lump. Clearly it would take a long time for these to weaken and disintegrate in the weather.