The end-Triassic extinction, roughly 201 million years ago, was driven by massive volcanic eruptions known as the Central Atlantic Magmatic Province, or CAMP. These eruptions flooded the atmosphere with carbon dioxide and other gases, triggering a cascade of environmental changes that wiped out roughly 76% of all species on Earth. It ranks among the five worst mass extinctions in the planet’s history.
The Volcanic Eruptions Behind It All
CAMP was not a single volcano. It was a sprawling system of lava flows, underground intrusions, and dike swarms that stretched across what would eventually become four continents as the supercontinent Pangaea began to break apart. High-precision dating places the critical magmatic events at around 201.5 million years ago, lining up tightly with the extinction itself. One dated dike swarm in northeastern Brazil extends roughly 360 kilometers, and similar formations appear across eastern North America, with samples from Canada dated to 201.464 million years ago.
What made these eruptions so lethal was not just the lava. The magma intruded into carbon-rich sedimentary basins in South America, specifically the Amazonas and Solimões basins in northern Brazil. When hot magma bakes through layers of organic-rich rock, it releases enormous volumes of carbon dioxide and other greenhouse gases far beyond what the lava alone would produce. This mechanism, magma cooking fossil carbon out of sedimentary rock, is now the leading explanation for how CAMP destabilized Earth’s climate so rapidly.
A Surge of CO2 and Rising Temperatures
The volcanic carbon release left clear fingerprints in the geologic record. A sharp negative shift of about 2 parts per thousand in carbon isotope ratios appears in rocks and fossils from the boundary between the Triassic and Jurassic periods. This kind of shift signals a sudden flood of light carbon into the atmosphere and ocean, exactly what you would expect from volcanic degassing and the burning of organic sediments. Oxygen isotope data from fossilized oysters at the same boundary show a simultaneous rise in sea surface temperatures, confirming that the carbon release drove significant global warming.
Fossil plant leaves tell a similar story from land. Both the size and density of stomata (the tiny pores plants use to absorb CO2 and release water vapor) decreased significantly at the Triassic-Jurassic boundary. Plants reduce their stomata when CO2 levels are high because they need fewer pores to get the carbon they need. Researchers estimate this stomatal shrinkage caused a 50% to 60% drop in water transpiration from plant canopies. That reduction likely increased surface runoff and erosion, degrading freshwater and coastal habitats and creating a link between terrestrial and marine biodiversity loss through disruption of the water cycle.
Ocean Acidification as a Kill Mechanism
Rising CO2 did not just warm the planet. It also dissolved into the oceans, making seawater more acidic. Boron isotope measurements from well-preserved fossil oysters at the Triassic-Jurassic boundary reveal a drop of at least 3.3 parts per thousand in boron isotope values, lasting approximately 50,000 years. This translates to a minimum ocean pH drop of 0.29 units, a substantial shift that would have made it far harder for shell-building organisms to survive.
The biological evidence lines up with the chemistry. Marine creatures that build calcium carbonate shells and skeletons were hit disproportionately hard. They were replaced in the aftermath by agglutinated foraminifera (tiny organisms that build shells from sediment grains rather than carbonate) and other “disaster taxa,” organisms that thrive in degraded environments. Carbonate sedimentation rates dropped worldwide, another sign that the ocean’s chemistry had turned hostile to calcifying life. Ocean acidification now appears to be associated with three of the five largest extinction events in Earth’s history.
What About an Asteroid Impact?
Because the dinosaur-killing extinction 66 million years ago was caused by an asteroid, it is natural to wonder whether a similar impact triggered the end-Triassic event. Elevated iridium levels (a metal often associated with extraterrestrial impacts) have been found in sediments near the Triassic-Jurassic boundary, and early researchers did consider a bolide impact as the cause. However, this hypothesis has been largely abandoned. No shocked minerals, no impact-melt spherules, and no crater of the right age have ever been identified. The iridium enrichment is now attributed to the CAMP eruptions themselves, since flood basalts can deliver platinum-group elements to the surface at levels well above normal crustal concentrations.
Which Species Disappeared
The end-Triassic extinction reshaped life on land and in the sea. In the oceans, reef-building organisms were devastated, ammonoid diversity collapsed, and conodonts (eel-like marine animals whose tiny tooth-like fossils are key markers in the geologic record) vanished entirely. Many bivalve and brachiopod lineages disappeared alongside them.
On land, the most dramatic turnover occurred among the archosaurs, the large group of reptiles that includes both the crocodilian lineage and the dinosaur lineage. Before the extinction, the crocodilian side of the family tree (Pseudosuchia) was enormously diverse, filled with large predators, armored herbivores, and forms that occupied ecological roles later taken by dinosaurs and mammals. The extinction wiped out nearly all of them. Only one lineage survived into the Jurassic: the crocodylomorphs, ancestors of modern crocodilians. This collapse cleared the way for dinosaurs to dominate terrestrial ecosystems for the next 135 million years.
How Long the Crisis Lasted
The main extinction pulse was geologically brief, but the environmental instability it triggered persisted far longer. Carbon cycle disruption, recorded as wild swings in carbon isotope values, continued for hundreds of thousands of years after the initial kill phase. The boron isotope evidence for ocean acidification shows the most intense acidification episode lasting around 50,000 years, coinciding with the main carbon isotope excursion.
Recovery was slow. Marine ecosystems took millions of years to rebuild their former complexity. Reef systems were especially sluggish to return, and it was well into the Early Jurassic before diverse carbonate-producing communities reappeared. On land, dinosaurs began diversifying relatively quickly after the extinction removed their competitors, but fully stable, complex ecosystems with layered food webs took considerably longer to re-establish. The end-Triassic extinction was, in effect, a reset button: brief in its killing, but long in its ecological aftermath.