Earth’s climate has never been static. Over hundreds of millions of years, the planet has shifted repeatedly between cold “icehouse” phases and much warmer “greenhouse” states. Scientists have long known that atmospheric carbon dioxide plays a central role in driving these swings. What has been less clear is where that carbon comes from and how it moves through Earth’s systems over deep geological time.
New research now shows that the movement of Earth’s tectonic plates has had a far greater influence on long-term climate change than previously understood. The study reveals that carbon is not released only where tectonic plates collide, but also where they slowly pull apart, fundamentally reshaping our understanding of Earth’s carbon cycle.
Published in the journal Communications Earth & Environment the research traces how plate tectonics have regulated global climate over the past 540 million years, offering a deeper view into the forces that control Earth’s temperature across geological eras.
The hidden role of the deep carbon cycle
At converging plate boundaries, chains of volcanoes known as volcanic arcs form. These volcanoes release carbon dioxide locked within rocks deep inside Earth, sending it into the atmosphere. For decades, this process was believed to be the dominant natural source of atmospheric carbon over geological time.
The new research challenges this idea by highlighting the importance of regions where tectonic plates move apart, such as mid-ocean ridges and continental rifts. These spreading zones allow magma to rise and play a key role in cycling carbon between Earth’s interior, the oceans and the atmosphere.
Oceans act as vast carbon reservoirs, absorbing carbon dioxide from the atmosphere and storing it in carbon-rich sediments on the seafloor. Over thousands of years, these sediments can accumulate to immense thicknesses. As tectonic plates slowly shift, they transport this carbon-laden material across the planet until it eventually reaches subduction zones, where plates sink back into Earth’s mantle and release carbon dioxide once again.
This long-term recycling process, known as the deep carbon cycle, connects plate movement directly to climate change on timescales far beyond human history. Using advanced computer models, researchers reconstructed how carbon has moved with tectonic plates across hundreds of millions of years.
Why plate motion determines greenhouse and icehouse worlds
The modelling revealed a clear pattern. During greenhouse periods, when Earth was warmer, carbon release from tectonic processes exceeded carbon burial in ocean sediments. During icehouse periods, carbon sequestration dominated, lowering atmospheric carbon dioxide and cooling the planet.
One of the study’s most significant findings is the central role of deep-sea sediments in regulating climate. As plates move, they transport carbon-rich sediments that ultimately re-enter Earth’s interior through subduction. This process turns out to be a major control on whether Earth tips toward warming or cooling.
The research also revises the long-held view of volcanic arcs as the primary carbon source. Volcanic arc emissions became dominant only in the last 120 million years, largely due to the rise of planktic calcifiers, microscopic marine organisms that evolved around 200 million years ago. These organisms transformed dissolved carbon into calcite, dramatically increasing the amount of carbon stored in seafloor sediments.
Before their spread, emissions from mid-ocean ridges and continental rifts played a much larger role in shaping atmospheric carbon levels than volcanic arcs.
What this means for understanding future climate
This research provides a new framework for understanding Earth’s climate system, one that goes beyond surface-level carbon emissions and atmospheric chemistry. It shows that climate is shaped by a delicate balance between carbon released from Earth’s interior and carbon locked away in ocean sediments, a balance controlled by the slow but powerful movement of tectonic plates.
While these processes operate over millions of years, understanding them is crucial for improving climate models and placing current human-driven climate change in context. Earth’s natural systems have regulated carbon for eons, but the rapid rise in emissions caused by human activity is occurring far faster than tectonic processes can counteract.
By uncovering how deeply Earth’s geology and climate are connected, the study underscores a simple truth: the planet’s climate story is written not only in the atmosphere, but also deep beneath our feet.