When earth’s climate changed, continental weathering intensified almost immediately

Around 201 million years ago, Earth experienced one of its major mass extinctions. The end-Triassic extinction marked a profound disruption to ecosystems worldwide and coincided with enormous volcanic activity associated with the Central Atlantic Magmatic Province.

As these volcanic systems released large amounts of carbon dioxide into the atmosphere, the global climate changed dramatically. But what happened to the continents in response?

Weathering is an important component of the long-term carbon cycle. When rocks are chemically weathered, atmospheric CO₂ can ultimately be removed through reactions that transport carbon to the oceans. Enhanced weathering can therefore act as a natural feedback to increased atmospheric carbon dioxide.

In a new study, an international team led by iC3 Polar Research Hub researcher Jochen Knies provides evidence that continental weathering intensified almost immediately alongside this major carbon-cycle disturbance.

Reading climate change in ancient sediments

The researchers investigated sedimentary records preserved offshore central Norway, using hyperspectral core imaging alongside geochemical evidence. Their results reveal a striking transformation in the minerals transported from land into the marine environment at the extinction level.

Figure: (A) Lithology, key biostratigraphic markers, and hyperspectral core image (HSI) classification types 1–6 for well 6206 with derived HSI intensity for kaolinite (2165 nm) and smectite (2205 nm) , and XRD results (wt.%) of single samples. HSI results for each core section (max. 1 m length) are displayed horizontally. (B) Tera-Wasserburg plots of U–Pb zircon data from two granitic gneiss clasts at 120.2 and 151.9 m. The intercept ages are considered to represent the age of crystallisation of the protolith to the granitic gneiss. Credit: Knies et al. (2026), Terra Nova.

One of the key signals is a rapid shift from smectite to kaolinite—clay minerals that can provide information about the intensity and character of chemical weathering on land.

At the same time, mercury anomalies preserved in the sediments provide an independent fingerprint of volcanic activity, while carbon and osmium isotope data help connect these changes to the wider environmental disruption associated with the end-Triassic extinction.

The continents responded rapidly

Together, these signals point towards a powerful conclusion: as volcanism released carbon dioxide—potentially raising atmospheric CO₂ to as much as four times pre-extinction levels—the continental weathering system responded rapidly.

Jochen Knies, iC3 researcher and lead author of the study, says:

“What surprised us most is how closely the weathering response tracks the volcanic carbon release. The geological record suggests that the continents were not simply passive recipients of climate change—they responded almost immediately.”

A natural experiment in Earth-system feedbacks

However, the timescale of this response has remained difficult to constrain from the geological record. Many models of the Earth system assume that continental weathering adjusts over relatively long periods.

The new findings provide empirical evidence for a much more immediate response during a major carbon-cycle perturbation. Jochen adds:

“The end-Triassic extinction gives us a remarkable natural experiment. It shows that when the carbon cycle is pushed far enough, changes on land can become visible in the sedimentary record almost synchronously with the carbon release itself.”

Multiple clues reveal a single story

The study also demonstrates the value of combining different geological tools. Hyperspectral imaging allows researchers to detect mineralogical changes within sediment cores, while mercury, carbon and osmium isotopes provide complementary evidence for volcanism, carbon-cycle disruption and changes in erosion and weathering.

Together, these independent signals strengthen the evidence for a rapid connection between volcanic carbon release, climate change and continental weathering.

Find out more

The paper “Instant Weathering Response to Carbon-Cycle Perturbations During the End-Triassic Extinction” is available open access in Terra Nova.

Lead author Jochen Knies is a researcher in the Department of Geosciences at UiT The Arctic University of Norway and at The Geological Survey of Norway. He is part of the iC3 Polar Research Hub where he leads a research unit that aims to reliably estimate how carbon cycles and ocean ecosystems altered during past ice sheet retreat. He additionally co-leads the Into the Blue project. His research focuses on reconstructing the past of the Arctic Ocean.