This wall-like feature is a left over from a plumbing system of an ancient volcano and is called a d

This wall-like feature is a left over from a plumbing system of an ancient volcano and is called a dykeordike. When this volcano was active, this dyke would have served as a duct through which magma was transport to feed the surface lava eruption, or alternatively it could have been an off-shoot from the magma chamber that froze up within a body of a volcano.

Now, ~15 million years later the erosion has removed much of this volcano and so its internal magma plumbing system is nicely exposed and is dominated hard crystalline rocks which are much harder to erode. Thanks to this contrast in erosion we have a beautiful landscape of the Warrumbungle National Park.