Did You Know a Giant Volcano Once Dominated South-East Queensland?
When you look at the lush mountains around the Queensland–New South Wales border, it’s hard to imagine that you’re actually looking at the eroded remains of one of Australia’s great ancient volcanoes!
Around 23 million years ago, a huge shield volcano developed around what is now Wollumbin (Mount Warning) in northern New South Wales.
And this wasn't a little volcanic cone.
The Tweed Shield Volcano stretched across an area of roughly 100 km by 80 km, reaching from around Lismore in the south to Tamborine Mountain in Queensland to the north. It rose to about 2 kilometres above sea level and poured enormous flows of basalt lava across the surrounding landscape.
And it wasn't all gentle lava flows!
Over roughly 3 million years, the volcano produced different types of volcanic activity, including basalt lava flows as well as more explosive eruptions involving rhyolite, ash and volcanic rock. Some lava flows were hundreds of metres thick.
Eventually, around 20 million years ago, volcanic activity ceased.
Then nature took over.
For the next 20 million years, rain, rivers and weathering gradually stripped away the softer volcanic rocks.
The harder rocks resisted erosion, leaving behind the spectacular landscape we see today.
And what about Wollumbin?
Wollumbin is the remaining central core or volcanic vent of the ancient volcano — essentially the hardened material that once occupied part of the volcano's internal plumbing.
But Wollumbin isn't the only remnant.
Springbrook, Lamington, Tamborine Mountain, the McPherson Range, Tweed Range and Nightcap Range are all associated with the eroded remains of this enormous volcanic landscape.
The huge bowl-shaped landscape surrounding Wollumbin is known as the Tweed Caldera.
But here's the fascinating part…
It isn't simply a gigantic crater left by one explosive eruption.
It is largely an erosion caldera, created over millions of years as softer basalt was worn away while more resistant volcanic rocks remained.
And that ancient volcano is still influencing life today.
The weathering of volcanic rocks produced rich soils, helping support the spectacular subtropical rainforests and agricultural landscapes of the Tweed region.
So next time you're enjoying the scenery around Springbrook, Tamborine or the Tweed Valley, remember…
You're looking at the remains of a volcano that was active around 23 million years ago!
From volcano… to mountains… to erosion… to rainforest.
Nature certainly takes its time!
Map Image background - By KHN45 - CC BY-SA 4.0 Other Images: These images may contain imperfections or artistic interpretation. To be used solely for educational, non-commercial history storytelling.
