Study Finds Earth’s Moving Surface Has Greater Impact on Climate Change

Earth’s climate has swung dramatically over its history, shifting between cold “icehouse” phases and warm “greenhouse” periods.

While these changes have long been linked to variations in atmospheric carbon dioxide, new research shows the sources of that carbon — and the forces controlling it — are more complex than previously thought. Scientists now say the slow movement of Earth’s tectonic plates plays a much larger role in regulating climate. Carbon is released not only where plates collide, but also where they pull apart.

Inside the deep carbon cycle

At converging plate boundaries, chains of volcanoes known as volcanic arcs release carbon dioxide stored in rocks deep within the Earth. For decades, these arcs were considered the main tectonic source of atmospheric carbon. The new research challenges that view. It finds that mid-ocean ridges and continental rifts — regions where tectonic plates spread apart — have been far more important drivers of Earth’s carbon cycle over most of geological history.

The oceans absorb vast amounts of carbon dioxide from the atmosphere, locking it into carbon-rich sediments on the seafloor. Over thousands of years, these sediments can accumulate to hundreds of metres in thickness. As tectonic plates slowly move, they carry this carbon-rich material across the planet. When it reaches subduction zones, where one plate sinks beneath another, the carbon is recycled into Earth’s interior and eventually released back into the atmosphere. This process is known as the deep carbon cycle.

Using computer models to reconstruct tectonic plate movements over the past 540 million years, scientists tracked how carbon was stored and released through time.

Greenhouse and icehouse worlds

The models accurately reproduced major greenhouse and icehouse climates. During warmer periods, carbon release outweighed carbon storage, driving higher atmospheric carbon dioxide levels. During colder icehouse phases, carbon burial in ocean sediments dominated, reducing atmospheric carbon dioxide and cooling the planet.

The study highlights deep-sea sediments as a critical control on Earth’s climate state. Their transport and recycling through subduction zones play a decisive role in determining whether the planet warms or cools.

Rethinking volcanoes

Volcanic arcs only became a dominant source of atmospheric carbon dioxide in the last 120 million years, the researchers found. This shift coincided with the rise of planktic calcifiers — microscopic marine organisms that convert dissolved carbon into calcite, creating carbon-rich seafloor sediments.

These organisms evolved around 200 million years ago and spread widely about 150 million years ago, increasing the amount of carbon recycled through subduction zones and released by volcanic arcs. Before that, emissions from mid-ocean ridges and continental rifts were the primary tectonic contributors to atmospheric carbon dioxide.

Why it matters

The findings offer a new way of understanding how Earth’s deep geological processes shape climate. Rather than being driven solely by atmospheric processes, climate is governed by a long-term balance between carbon released from Earth’s interior and carbon locked away in seafloor sediments.

This deeper perspective is important for improving climate models and understanding how Earth responds to rising carbon dioxide levels — including those caused by human activity.