"Volcanic activity along Australia's east coast over the last 35 million years which are rich in soil nutrients, ideally suited to the survival of the rainforests."
"You are now standing on the remnants of a volcano that was active some 24 million years ago. The eastern part of the Main Range shield volcano once spread across the Fassifern Valley, probably as far as Mt Maroon, Boonah and even to Ipswich, while the western side of the volcano spread to at least Warwick."-sign on Mount Cordeaux.
The views from Mount Cordeaux are beautiful, in particular, you can see Mount Mitchell.
"Did you know?
Fassifern Valley's peaks began deep beneath the main Range volcano. Composed of different rock types separated from basalt magma at great depths, these peaks were formed as plugs, dykes or sills when magma entered numerous cracks and weaknesses in underlying older rocks, as well as moving up the main vents. As the volcano and some of the underlying rocks were eroded away, any plugs, dykes or sills composed of resistant rocks, particularly those of rhyolite and trachyte, remained as steep peaks."- from the sign on the trail.