Rock surface | LostPizzaBoy
Audio tour 12 - Geology
- Location: Car sunset viewing area | Duration: 4m05s
- Download audio tour 12 | Geology (MP3 - 9.36 MB)
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Anangu believe this land was created by their creation ancestors, who travelled the land leaving marks in the landscape and laws for people to live by. Geologists have a different belief as to how Uluru and Kata Tjuta came to be.
Uluru and Kata Tjuta are millions upon millions of years old. Geologists say their formation began about 550 million years ago.
Back then, the Peterman Ranges to the west of Kata Tjuta were much taller than they are now. Rainwater flowed down the mountains, eroding sand and rock and dropping it in big fan shapes on the plains. One fan had mainly water-smoothed rock and the other was mainly sand. Both fans became kilometres thick.
Then 500 million years ago, this whole area became covered in sea. Sand and mud fell to the bottom of the sea and covered the seabed, including the fans. The weight of this new seabed turned the fans into rock. The rocky fan became conglomerate rock while the sand fan turned into sandstone.
About 400 million years ago the sea disappeared. Rocks folded and tilted as the earth’s tectonic plates shifted. The rocky fan tilted slightly. The sand fan tilted 90 degrees so the layers of sandstone stood on end.
Over the last 300 million years, softer rocks have eroded away, leaving parts of the old fans exposed. Kata Tjuta is the hard part of the old rocky fan. Uluru is part of the sand fan, with its nearly vertical beds of sandstone.
30,000 years ago, the area around the two icons was covered in windblown sand plains and dunes. What we see at Uluru and Kata Tjuta today, are just the tips of huge rock slabs that continue below ground for up to six kilometres.
If you take the Base Walk, you’ll get up close to Uluru and see how weather-beaten it is - with its holes and gashes, ribs, valleys and caves.
Uluru is made up of a type of rock called arkose. Some arkose layers are softer and wear away more quickly. This leaves Uluru’s parallel ribs or ridges.
If you stand up close to Uluru you’ll notice the surface is actually flaky red with grey patches. These flakes are bits of rock left after water and oxygen have decayed minerals in the rock. The red is the rusting of iron found naturally in arkose and the grey is the original colour. Inside the caves you can see this original grey colour. Caves can be formed by uneven flaky weathering. Small pits become bigger dimples, then hollows, then caves.
Water has shaped the valleys, potholes and pools of Uluru. For millions of years rainstorms have sent water plummeting down the hard rock, wearing it away to form grooves, chains of potholes and pools.
Kata Tjuta’s famous domes formed from factures in the rock, when 400 million years ago it was folded and fractured. Water seeped down the cracks and over millions of years the rock eroded away - grain by grain, pebble by pebble - to form valleys and gorges that split the rock slab into blocks. Curved cracks formed on the surface of the blocks. Weathering and erosion wore away the rocks above the cracks to produce the rounded domes you can see today.