Ayers Rock, or Uluru, as it is called today, has a complex geological history. Uluru used to be considered the largest freestanding stone in the world, but it appears to be anchored in the earth to a depth of six kilometers.
About 550 million years ago there was a granite mountain range, Petermann Ranges, west of Uluru. This mountain range slowly deteriorated, and the water carried large amounts of sediment, especially sand, to the east. The sediment layer was, after all, many kilometers thick. About 500 million years ago the area was flooded by the sea. Marine deposits compressed the sand of the Petermann Ranges into a kind of sandstone called ancillary.
However, the sea disappeared again, and strong geological forces at the same time bent and tilted the sandstone, so the geological layer that now forms Uluru came to stand on its side. Wind and weather eroded layer after layer. However, as the sandstone that would later become Uluru became more massive, it was less likely to wear away and form an island mountain.
Now Uluru rises 348 meters above the sand in the Simpson desert. Seen from above, the original 550 million-year-old geological stratification is clearly visible, especially because the rain has carved deep gullies into it.