An eruption of continental scale
Around 511 million years ago, during the Cambrian Period, a vast section of the supercontinent Gondwana split open. From enormous fissures in the crust, rivers of basaltic lava poured out, not from a single volcano, but across a massive area of what is now northern and central Australia. The Kalkarindji Large Igneous Province (LIP) was a continental flood basalt event among the largest volcanic episodes of the last billion years.
The total area covered by these lava flows is estimated to have exceeded 2.1 million square kilometers, with a volume of at least 500,000 cubic kilometers. Individual flows were 20 to 60 meters thick, and in some areas, such as the Antrim Plateau, they stacked up to a total thickness of 1.5 kilometers. The eruption occurred in rapid pulses, with the bulk of the lava being emplaced in a geologically brief period of one million years or less. Today, the eroded remnants of this province are found across the Northern Territory, Western Australia, and parts of Queensland and South Australia, known by names like the Antrim Plateau Volcanics and the Table Hill Volcanics.
A trigger for extinction and evolution
The Kalkarindji event occurred at the same time as the Early–Middle Cambrian extinction event (ca. 510–511 million years ago), the first major mass extinction of complex, multicellular life. Researchers have demonstrated a near-perfect chronological correlation between the eruption and the extinction, with a probability of coincidence calculated at one in 20 billion. The eruptions released large quantities of sulfur dioxide, carbon dioxide, and methane into the atmosphere.
The sulfur dioxide would have caused short-term global cooling and acid rain, while the greenhouse gases led to long-term warming and ocean acidification. Geochemical analysis of the volcanic rocks shows a depletion of sulfur, indicating it was released into the atmosphere. These rapid climate shifts and the depletion of oxygen in the oceans likely caused the extinction, which wiped out an estimated 50% of marine species, including many families of trilobites. Paradoxically, the long-term weathering of the immense new basalt fields would have released a flood of nutrients like phosphorus into the oceans. This fertilization could have spurred the evolution and diversification of new species in the aftermath of the extinction, contributing to later pulses of the Cambrian Explosion of life.