Mount Warning is the central remnant (volcanic plug) of an ancient shield volcano, the Tweed Volcano, formerly twice the height of the current mountain, which erupted 22 million years ago. The erosion caldera formed since this eruption is easily visible around the summit and forms the rim of the Tweed Valley. One of the mountains that were formed by its eruption was Tamborine Mountain
Tweed has moved off its hot spot over the millions of years.