This view south-east over the Matiri Range near Murchison shows the Hundred Acre Plateau (1), Thousand Acres Plateau (2), the Haystack (3) and Mt Owen (4). The Thousand Acres Plateau is made of limestone from the Oligocene Period (32–22 million years ago). This sits on top of Eocene sandstone (55–33.7 million years old). Softer mudstone, originally on top of the limestone, has been eroded away as the mountains were uplifted. There are few caves here, as the limestone is too impure for good cave formation. The pure marble of Mt Owen, in the distance, is riddled with caves.