Uluṟu-Kata Tjuṯa National Park
15 December 2005
The origins of Uluru (and Kata Tjuta) date back about 500 million years, to around the same time the Australian continent was formed.
Large crustal blocks were merging together to create the island of Australia — a process similar to the way India is ramming into the Eurasian continent today. As a result, Himalayan-sized mountain ranges were being built.
The rocky material that ultimately became Uluru and Kata Tjuta was in one of the mountain ranges formed — the Petermann Ranges.
The newly-formed Petermann Ranges were similar in size to the French Alps or the Himalayas. But without any plant cover they eroded rapidly.
The sediments that make up Kata Tjuta were moved by a river system into an alluvial fan.
However, the sand that became the arkose sandstone of Uluru was dumped at the bottom of the mountain range.
After this long period of rapid mountain building and erosion the centre of Australia turned into an inland sea and a phase of deposition began in what is now known as the Amadeus Basin.
Around 400 million years ago the sands and gravels of Uluru and Kata Tjuta were so far down, and under so much pressure, they changed from sediment into rock.
Another mountain-building event, known as the Alice Springs Orogeny, began around this time. Over millions of years, this event created the great big folds visible when you fly over Central Australia today. The rocks making up Uluru and Kata Tjuta were also involved.
After a long phase of erosion that lasted hundreds of million of years, Uluru and Kata Tjuta eventually emerged from the softer rocks.
The deformation flipped the sediments on their side so the originally horizontal layers of sand and gravel, known as the ‘bedding planes’, are now vertical.
And the rock is incredibly hard.
The red colour of Uluru is due to the oxidation or the rusting of the iron-bearing minerals within the rock as it has sat there in the desert air for hundreds of thousands of years