Lamington National Park – Binna Burra – Rosins Lookout on Numinbah Valley, Springbrook Plateau, Mount Warning Wollumbin and Ship Stern
Looking down into the Numinbah Valley trough the gap in the mountains is Mount Warning Wollumbin the remnant plug from the central vent of the ancient Tweed Shield Volcano.
The landscape around you has taken 23 million years of building and reshaping to form one of the world’s best example of a Shield Volcano Caldera and the only one surrounded by World Heritage listed subtropical rainforest.
The Tweed Shield Volcano was formed trough successive eruptions of lava flows 23-20 million years ago. Basalt and rhyolite lava spread out to Lismore in the south, Mount Tamborine in the north and Kyogle to the west and was 2000 m deep.
Nearly twice the present heigh of Mount Warning Wollumbin, the rounded sloping sides of the volcano attracted high coastal rainfall that etched radiating streams out along its flank, Those streams deepened and broadened and with prevailing wind and high rainfall formed the gap in the northern wall of the caldera escarpment to become Numinbah Valley, carved by the Nerang River. Today some of the major rivers, and minor streams, follow the drainage lines very similar to those that were established over 20 million years ago on the flanks of the volcano.
If you look closely you can see how the lava flows and their erosion have created an incredibly complex landscape. Notice the different lines of vegetation caused by the different soil types – Eucalyptus on the lower ridges of easily erodible rhyolite and temperate rainforest higher up on the rich basalt.
The rounded formation of the top of some of those cliffs is formed of particularly resistant basalt and beneath that are the exposed cliffs of the softer more erodible rhyolite which has created the prominent cliff lines of Springbrook Plateau and spires of Ship Stern.
For over a hundred thousand years, those deep valleys conserved moisture and provided a fertile refuge for Gondwana rainforest and the animals while other habitats come under great pressure trough the Great Drying period of the Pliocene period (causing the aridity of central Australia). Despite European cultivation, this broad region still has one of Australia richest areas of biodiversity.