The Volcanic Eruption That Covered One Third of Australia

The Kalkarindji Flood of Fire: When Australia Turned to Lava

Roughly 511 million years ago, long before dinosaurs or forests or even fish with jaws, Australia was part of a vast southern supercontinent called Gondwana. The land was quiet, mostly flat, and covered in shallow seas full of strange early animals — trilobites, worm-like creatures, sponges, and the first reef builders.
It was the Cambrian Period, the dawn of complex life. But deep beneath the surface, the planet was brewing something enormous.

Under what is now northern and western Australia, the mantle — that vast layer of hot, plastic rock beneath the crust — began to stir. Pressure and heat built for thousands of years, until one day the continent cracked open. From those fissures poured rivers of molten basalt, hundreds of meters thick, flooding the land for hundreds of thousands of square kilometres.

This wasn’t a normal volcanic eruption. It was one of the biggest geological events in Australian history — a continent-sized outpouring of lava called the Kalkarindji Large Igneous Province, or simply the Kalkarindji flood basalts.

And this ancient flood of fire didn’t just reshape the land. It may have changed the planet’s climate — and possibly even triggered one of the first mass extinctions in Earth’s history.

The Calm Before the Eruption

To understand what caused it, we need to picture what Australia was like back then.

In the Cambrian, the North Australian Craton — one of the oldest, most stable chunks of the continent — sat near the equator. Surrounding it were broad sedimentary basins: the McArthur Basin, the Georgina Basin, and others, filled with layers of limestone and shale laid down in warm, shallow seas.

The crust here wasn’t completely quiet. It had already been through billions of years of tectonic stretching and heating, including an earlier magmatic event called the Warakurna Large Igneous Province. That left the mantle beneath northern Australia chemically “fertile” — ready to melt again if given the chance.

So what finally set it off?

Most geologists don’t think it was a deep mantle plume like the ones that created Hawaii or the Deccan Traps in India. Instead, it may have been something subtler — edge-driven convection.
That’s when heat starts swirling at the boundary between thick, stable crust and thinner, weaker crust nearby. The difference in thickness causes mantle material to circulate upward on one side — like hot air rising next to a cold wall — and as it rises, it starts to melt.

Over time, this created huge pockets of magma under northern Australia. The molten rock slowly worked its way upward, collecting in vast underground chambers. The pressure built and built until the crust finally gave way.

When the Earth Tore Open

When the eruption finally began, it wasn’t like anything we’d recognize as a volcano today. There were no cones or craters — just massive cracks ripping open the Earth’s surface for hundreds of kilometres.
From these fissures, lava gushed out in unimaginable quantities, spreading across the landscape like a fiery ocean.

Geologists call this kind of event a continental flood basalt. The name fits — the lava literally floods the land, sometimes covering areas the size of modern countries.
In Kalkarindji’s case, it covered more than two million square kilometres — roughly the size of modern Greenland — stretching from the Kimberley region of Western Australia, across the Northern Territory, and possibly as far south as central Australia.

Each individual flow might have been 10 or 20 meters thick, and they came one after another in quick succession. In some places, like the Antrim Plateau, the total pile of lava still measures over a kilometre thick today.

Imagine standing on a Cambrian shoreline and seeing that — a glowing horizon of molten rock advancing silently across the plains, filling valleys, swallowing rivers, vaporizing everything in its path.
And it didn’t just happen once. It likely happened again and again, for hundreds of thousands of years, until the whole northern half of the continent was buried in black basalt.

What the Rocks Tell Us

If you visit the Northern Territory today, you can still see the remains of these ancient lava flows. The Antrim Plateau Volcanics form long escarpments and black cliffs, their surfaces often covered in iron-rich red soils. The rock is full of vesicles — little holes that once held gas bubbles — now filled with quartz, calcite, and colorful zeolite minerals like analcime and stilbite.

*Image depicts the Antrim Plateau Exposed Lava Layers today.

Chemically, the rocks tell a consistent story. They’re low in titanium, enriched in trace elements like rubidium, barium, and thorium, and they all share an unusual isotopic fingerprint. That fingerprint hints at a deep origin — a mantle source that had been “seasoned” by ancient subduction, way back in the Archean or early Proterozoic.
In other words, the melting mantle had inherited some of its chemical character from oceanic sediments that sank into it billions of years earlier. When that mantle finally melted, those ancient impurities showed up in the lava.

When Fire Met Water

Not every eruption was peaceful. Some of the most fascinating Kalkarindji rocks are phreatomagmatic breccias — basically, volcanic debris created when magma exploded on contact with water.

Back then, much of northern Australia was covered in shallow seas. When lava poured into those waters or met groundwater, it caused steam-driven explosions.
The evidence of these explosive interactions is preserved as layers of broken basalt fragments, welded together into rock.

These eruptions released staggering amounts of sulfur dioxide, carbon dioxide, and methane — enough to cause dramatic climate swings. Sulfur aerosols would have cooled the planet for years at a time, while CO₂ and methane trapped heat for millennia afterward.
This one-two punch — cooling, then warming — can devastate ecosystems, especially those living in shallow seas.

And right around this time, something strange happened in the fossil record: a sharp drop in biodiversity. Many early Cambrian marine species vanished, marking the first mass extinction of the Phanerozoic Eon.
The timing lines up almost perfectly with the Kalkarindji eruptions.

When the World Got Sick

It’s hard to overstate how much gas a province like this could have released. Modern estimates suggest that the Kalkarindji eruptions might have emitted 1.6 million trillion grams of CO₂ — about 1.7 percent of all the carbon in Earth’s atmosphere at the time. That’s enough to raise global temperatures significantly, acidify the oceans, and throw the carbon cycle out of balance.

Sulfur emissions would have added their own chaos, creating short-lived volcanic winters.
And when the lava intruded into underground layers of oil, gas, and sulfate minerals, it likely triggered massive secondary reactions — releasing even more methane and sulfur compounds.

The result: wild climate swings, collapsing food webs, and oxygen-starved oceans.
Sedimentary rocks from this time show signs of marine anoxia — black shales loaded with organic carbon and pyrite — suggesting that oxygen levels in the ocean dropped drastically.

The Cambrian extinction that followed wiped out nearly half of known marine genera, including many early trilobite families and the reef-building archaeocyathids.
While scientists still debate whether Kalkarindji was the sole cause, it was almost certainly a major contributor. It was Earth’s first real taste of how catastrophic large-scale volcanism could be for life.

Beneath the Lava: Heat, Oil, and Stone

While life at the surface suffered, deep below the crust something else was happening.

In the McArthur Basin, ancient organic-rich shales from the Proterozoic were being cooked by the heat of the overlying lava. The basalt blanket was sometimes half a kilometre thick — enough to trap heat for hundreds of thousands of years.
This thermal pulse matured buried hydrocarbons, turning solid kerogen into liquid oil and gas. In a sense, the Kalkarindji event didn’t just cause extinction — it also kickstarted petroleum formation in one of the world’s oldest known oil systems.

That’s why modern energy companies study the event closely. The Beetaloo Sub-basin, for instance, still bears the fingerprints of this Cambrian heating episode. Without it, many of its hydrocarbons might never have formed at all.

The End of the Inferno

Eventually, after hundreds of thousands — maybe a few million years, the eruptions began to die down. The cracks sealed. The magma chambers cooled.
The continent, once a sea of lava, slowly returned to calm.

Over time, groundwater seeped through the hot basalt, depositing secondary minerals — zeolites, calcite, quartz — in cracks and vesicles. The black rocks weathered into rich, red soils. Rivers began to carve valleys through the cooled lava, and new layers of sediment were laid down above it.
By the end of the Cambrian, the Kalkarindji landscape would have looked like a vast, dark plateau fringed by shallow seas.

The eruption left behind no towering volcanoes, no calderas. Flood basalt provinces almost never do. Instead, their legacy is subtle — a geochemical fingerprint in the crust, a blanket of basalt, and a shift in the trajectory of life.

Today, much of the province remains buried beneath younger sediments, invisible at the surface.
But the total area covered by lava may have been even larger than we think — perhaps 2.5 million square kilometres before erosion took its toll.

Legacy of Fire

So what’s the takeaway from all this ancient drama?

The Kalkarindji LIP shows us that even half a billion years ago, the Earth’s interior was capable of reshaping the surface on a continental scale — and that such events could already influence climate and life.
It was the first flood basalt province to erupt into a world full of complex animals, and the first to leave a mark on the biosphere we can clearly trace.

In a way, Kalkarindji bridges two worlds:

The Precambrian Earth, dominated by internal geology, and

The Phanerozoic Earth, where geology and biology began to intertwine.

The Kalkarindji Large Igneous Province may not be famous like the Deccan Traps or the Siberian Traps. But it deserves to be. It was Australia’s first great inferno, and it marked the moment when our ancient continent truly made its fiery debut in the Phanerozoic world.

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