Around 200 million years ago during the Early Jurassic, the supercontinent Pangea began to fragment, dramatically reshaping Earth’s surface. As the landmass split apart, continents drifted away from one another and vast new oceans formed, gradually creating the global geography we recognize today. For decades, geoscientists believed that the Pangea breakup was primarily driven by a buildup of heat trapped beneath the enormous supercontinent. Because continents are thicker than oceanic crust, they were thought to act like insulating blankets, slowing the escape of heat from Earth’s interior and allowing temperatures in the underlying mantle to rise over tens of millions of years.
According to this traditional view, when tectonic forces eventually stretched and fractured the supercontinent, the accumulated heat helped generate large amounts of magma. This process could produce thick new oceanic crust and trigger enormous volcanic eruptions, including the formation of massive lava provinces such as the Central Atlantic Magmatic Province. Such events appeared to support the idea that the Pangea breakup was the result of a globally overheated mantle beneath the supercontinent.
However, new research published in Earth and Planetary Science Letters challenges this long-standing explanation. Scientists analyzed the thickness of some of the earliest oceanic crust that formed when the Atlantic and Indian oceans began opening during the initial stages of the Pangea breakup. Because hotter mantle produces more melting and therefore thicker oceanic crust, crustal thickness can serve as an indirect indicator of mantle temperature in the distant geological past.
The results reveal a more complex picture than previously assumed. Instead of consistently thick oceanic crust that would indicate a uniformly overheated mantle, researchers found that crustal thickness varied across different regions. The measurements cluster into two groups: one averaging around 5.5 kilometers and another around 6.7 kilometers. Interestingly, the thinner group—primarily from the Equatorial Atlantic—is actually below the present-day global average of about 6.1 kilometers. Scientists suggest this may reflect relatively cooler conditions linked to thick continental lithosphere that existed in equatorial regions before rifting began.
The thicker crustal group is only modestly above modern averages. Researchers estimate that mantle temperatures in these areas may have been elevated by just 9–15°C, with some localized regions in the Central Atlantic potentially reaching increases of up to about 60°C. Even these values fall far short of what would be expected if the mantle beneath the entire supercontinent had experienced extreme heat buildup prior to the Pangea breakup.
The study also investigated how crustal thickness changed over time. Statistical analysis suggests only a slight increase in crustal thickness with age, roughly 1.5 meters per million years. This implies a gradual mantle cooling rate of about 0.04–0.06°C per million years over the past 180 million years. Remarkably, this rate aligns closely with estimates of Earth’s long-term secular cooling, which describe the slow loss of heat from the planet’s interior over billions of years.
Taken together, the findings indicate that the mantle beneath the Atlantic and Indian oceans was not dramatically overheated when Pangea fragmented. Instead, the Pangea breakup likely resulted from a combination of tectonic forces and regional geological conditions rather than a single global heat buildup. Factors such as plate stresses, variations in mantle composition, and pre-existing weaknesses in the continental lithosphere may have made certain regions more susceptible to rifting.
Understanding the mechanisms behind supercontinent cycles is crucial because they influence long-term climate, ocean circulation, sea level and even biological evolution. By examining crustal thickness and mantle temperature estimates, the new research suggests that the Pangea breakup was driven by subtle temperature variations and complex tectonic interactions deep within Earth rather than by an extreme surge of internal heat.
https://phys.org/news/2026-02-earth-mantle-cooler-thought-pangea.html