The Supervolcano in Queensland: The Mungore Caldera

The Forgotten Supervolcano of Queensland: Mungore’s Lost Eruption

If you’ve ever looked at a map of southeast Queensland, you might never guess that beneath those rolling paddocks and granite hills lies the eroded scar of a cataclysm so enormous it rivals Yellowstone and Taupō. It’s called the Mungore Caldera, and though few Australians have ever heard of it, it was once the stage for one of the most violent volcanic events our continent has ever known.

Today, there’s no steaming lake or rising dome, no fumaroles or geysers to hint at its fiery past. Instead, the land wears a cloak of quiet — cattle graze where magma once churned; farmhouses sit where incandescent clouds once roared. But 220 million years ago, in the Late Triassic, this peaceful part of Queensland tore itself open in a super-eruption that may have not only changed the face of eastern Australia, but the planet itself.

Mungore's Location

But first things first. Location. Finding the Mungore caldera was a tricky little bugger. But I managed to find it after doing some geological sleuthing. Firstly, keep in mind that the land has changed after this caldera erupted. The Mungore Caldera was sliced by the Perry Lineament, which offset its eastern third about 8 km northward (sinistrally). This has warped the once circular shape of the caldera. Thankfully, geophysical tools can be used to help picture the size and scope of this massive structure. When viewed under gravity, we can see two circular shapes. Another thing we see are ring faults. Radial structures created by the caldera collapse. But what allowed me to really zero in on its location is this layer which represents a granite called the Mungore granite. 

The alteration that occurred to the land not only distorts the shape of the original supervolcano caldera, but it also created pathways for mineral-rich fluids that still define much of the gold-copper exploration belt there today.

*Location of the Mungore Caldera

The Mungore Caldera showing the displacement on its eastern side that occurred.

*Image shows the Mungore Caldera under a Gravity Scan.

A Continent on the Edge

To understand how Mungore came to be, we need to step back in time, before the dinosaurs we know from Jurassic Park even existed. In the Late Triassic, around 221 million years ago, Australia was still welded to Antarctica and other fragments of the supercontinent Gondwana. The eastern edge of the landmass — what geologists call the New England Fold Belt — was a restless place, a patchwork of island arcs, oceanic crust, and continental fragments that had been colliding and welding together for hundreds of millions of years.

For much of the Paleozoic Era, this part of Australia was a subduction zone, a bit like modern-day Chile or Japan. An oceanic plate was diving beneath the edge of Gondwana, melting as it sank and feeding long chains of volcanoes along the margin. Those arcs built up mountain belts, and each collision and accretion event left its mark in the form of folded rocks, thrust faults, and granitic intrusions.

*Image depicts a subduction zone along with arrows that indicate the compressive stress experienced.

By the Late Triassic, though, something began to change. The once-compressed margin started to relax — the grinding subduction slowed, the mountains began to spread, and the crust started to stretch. It was the first sign of a transition from a compressional plate boundary (where plates collide) to an extensional one (where they pull apart). That shift would eventually lead, tens of millions of years later, to the opening of the Tasman Sea and the birth of modern eastern Australia.

*Image depicts a stalled subduction zone and the beginning of extension.

When continental crust stretches, it doesn’t do so quietly. Deep beneath the surface, the hot mantle starts to well up, and new batches of magma intrude into the crust. Some of these magmas stall and cool to form granites. Others, buoyed by gas and heat, push toward the surface, melting and mixing with the surrounding rock as they go. The result is an enormous, unstable reservoir of silicic magma — the kind rich in silica, viscous and explosive, capable of feeding catastrophic eruptions.

That’s exactly what was brewing beneath what is now the Mungore region of Queensland.

The Birth of a Magma Giant

The first signs of the Mungore system were relatively gentle: rhyolite domes oozed up through the surface, solidifying into glassy lava mounds. These were the heralds of something much bigger to come — the early “vents” that marked where the crust was beginning to yield.

Beneath them, a huge magma chamber — perhaps 10 or 15 km across and several kilometres deep — was assembling. It wasn’t a single, tidy body of molten rock but a mush of crystals, melt, and gases; a simmering stew connected to deeper basaltic intrusions that kept it hot and buoyant. The magma itself was rhyolitic, a sticky, silica-rich composition produced by melting and re-melting of andesitic crust, with a pinch of basaltic input from the mantle.

Pressure built for perhaps tens of thousands of years. The chamber ballooned, and cracks propagated upward. When the roof finally gave way, it wasn’t a single vent that opened, but an entire region that failed catastrophically.

The Day the Sky Went Dark

Imagine standing anywhere within a hundred kilometres of the caldera when the eruption began. The ground would have convulsed as magma punched its way through, blasting apart the overlying rock. Columns of ash and pumice would have climbed tens of kilometres into the stratosphere, spreading out like giant mushroom clouds. Lightning would have laced through the darkness, igniting fires in the forests below.

The size of the caldera alone is 50 km by 35 km, and it tells us we’re dealing with something on the order of 1,000–2,000 km³ of erupted material. That’s the range of VEI 8 events, the largest eruptions known in Earth’s history. For comparison, Yellowstone’s last super-eruption released about 1,000 cubic kilometres, and the Taupō eruption in New Zealand about 1,170 km³. Mungore’s eruption either matched or exceeded them.

Ash clouds would have blackened the sky across the Triassic landscape, burying everything in their path. The surrounding basins would have filled with searing ignimbrite flows — pyroclastic surges so hot and fast they travelled at highway speeds, vaporizing forests and boiling lakes. These flows welded into dense, glassy rock that we now see preserved as intra-caldera quartz ignimbrite, found interlayered with bedded rhyolite breccias inside the old volcanic basin.

The eruption likely lasted days to weeks, cycling through phases of column collapse, fountain-fed flows, and caldera collapse. Each phase would have emptied more of the magma chamber, causing the land above to sink further and further. A volcanic winter inevitably followed.

The Collapse of the Caldera

When a magma chamber that size is partially drained, the crust above it can’t support its own weight. It collapses — sometimes gradually, sometimes catastrophically — along ring faults that encircle the chamber like the edges of a giant piston. That’s exactly what happened at Mungore.

As the eruption raged, sections of the crust sagged inward by hundreds of meters, then kilometers, producing a vast collapse cauldron — a 50 × 35 km ovoid depression oriented east-west, cutting across the region’s older north-northwest structural grain. The fault-bounded margins of the caldera were marked by ring dykes of porphyritic biotite granite and rhyolite, some up to 200 m thick, intruded along the collapsing edges like molten stitches holding the wound together.

In the aftermath, the centre of the caldera was a wasteland — a steaming, ash-filled depression kilometres deep, ringed by shattered fault scarps and domes of still-cooling lava. Inside that depression, enormous quantities of hot ash and pumice continued to pour in, accumulating to thicknesses of perhaps a kilometre or more. These layers welded into the massive intra-caldera ignimbrite sequences we see today, sometimes intruded by younger granites that represent the lingering heat of the system.

*Image shows Ring Faults within the Caldera.

Resurgence and Recovery

After the main eruption ceased, the magma chamber didn’t go cold right away. It refilled, partially, with new magma — a process known as resurgence. The floor of the caldera began to dome upward again as molten granite pushed its way back into the base of the depression. This produced a body of weakly porphyritic biotite granite, texturally homogeneous and chemically similar to the rhyolites that erupted earlier. Geologists interpret this as a resurgent pluton — the frozen heart of the volcano as it tried, unsuccessfully, to come back to life. And this pluton is actually visible when using gravity images. You can see two domes where magma attempted to reach the surface. It’s little things like this that really leave me awe-struck and they remind me of why I’m so fascinated by geology. We get to not only see the caldera shape, but the places where, post eruption, this caldera struggled to stay alive before finally giving in to its demise.

So, by this stage, the supervolcano was effectively dead. The eruptions had spent their fury, the remaining magma congealed, and the once-towering volcano collapsed into itself. Rain and wind began the slow, patient work of erosion, carving valleys through the tuff and granite. Within a few million years, vegetation returned, life crept back across the scar, and the caldera faded into geological memory.

Mineral Riches

It turns out the Mungore supervolcano didn’t just leave behind ash and granite — it also left behind metal. Today, more than 200 million years after the eruption, geologists and exploration companies are combing the same hills, searching for traces of gold, silver, copper, and molybdenum. ActivEX Limited, one of the companies working in the region, holds permits right over the old caldera margin, where the ancient Perry Fault Zone cuts through the volcanic and granitic rocks. That fault — the same one that helped Mungore’s magma reach the surface in the first place — still marks zones where mineral-rich fluids once surged upward through the fractured crust. Those fluids cooled, crystallising veins of quartz laced with metals.

Life After Death: The Mungore Complex Today

What survives today is subtle — but to the trained eye, unmistakable. The Mungore Complex forms a broad, elliptical zone of granites, rhyolites, and ignimbrites, their textures and chemistries revealing the fingerprints of that ancient cataclysm.

The region also preserves a second volcanic structure immediately adjacent to Mungore — a cluster of rhyolite domes and a broad regional sag. Some researchers believe this may represent a second caldera, formed by a companion eruption in the same magmatic system. Together, the pair mark a volcanic province of staggering proportions — a field of rhyolite and granite that once must have rivalled the volcanic plateaus of New Zealand and western North America.

A Supervolcano Hidden in Plain Sight

The irony of Mungore is that, unlike Yellowstone or Taupō, it’s been so thoroughly eroded and buried that it almost escaped notice. There are no dramatic cliffs or giant caldera lakes to betray its existence. For decades it was simply mapped as a “granitic complex.” Only with detailed geochemical and structural work in the 1990s did geologists realise they were looking at the remains of a collapsed caldera system — and not a small one.

So, in every way that matters — size, structure, and eruptive sequence — Mungore fits the template of a VEI 8 supervolcano. The largest volcanic eruptions known to exist.

But because the deposits are deeply eroded and no direct ignimbrite volume has been measured, geologists still refer to its eruptive output as “unquantified.” Even so, by comparing it to similar-sized calderas, a reasonable estimate of 1,000–2,000 km³ of erupted material fits perfectly — enough to blanket half of eastern Australia under meters of ash. Because of this, it’s difficult to escape the conclusion that Mungore was a global-scale volcanic event.

From Fire to Stone

Today, if you walk along the old quarries and road cuttings near Gayndah or Mount Perry, you can still find the relics — welded ignimbrite with flattened pumice fragments, rhyolitic breccias with shards of volcanic glass, and granites that once crystallized kilometres below the surface of the eruption. Every mineral grain — quartz, feldspar, biotite — tells part of the tale.

So next time you hear about Yellowstone’s restless magma or Taupō’s explosive past, remember that Australia has its own giants — they’re just older, quieter, and hidden beneath the dust of time.

Here's the video we made on this on the OzGeology YouTube Channel: