How An Ancient Bridge Formed By A Continental Collision Forever Changed Life On Earth

AUSTIN, Texas — Two continents collided millions of years ago, forming a bridge that changed Earth’s climate system and triggered one of history’s greatest animal migrations. Recent research reveals how the closure of an ancient ocean passageway reshaped our planet in ways we still experience today.

The study, published in Nature Reviews Earth & Environment, examines what happened when the Arabian and Eurasian plates crashed together, closing the Tethys Seaway – an ocean corridor that once divided Africa and Eurasia. This continental collision around 20 million years ago created a land connection that altered Earth’s future trajectory.

“This collision was governed by plate tectonics and mantle convection and had profound impacts on ocean circulation, biogeography and the climate system beyond the Eastern Mediterranean-Tethyan realm,” explains the research team, led by Eivind O. Straume during his time as a postdoctoral fellow at the University of Texas at Austin.

The remarkable discovery centers on the role of Earth’s deep interior. While scientists knew moving continents drove this collision, this study highlights how hot rock from near Earth’s core – called the Afar plume – pushed up land and helped close the seaway.

This molten material didn’t just raise the Ethiopian highlands. It formed a flowing belt of rock that traveled northward beneath Earth’s crust, lifting the Arabian peninsula and helping build the land connection between Africa and Eurasia.

“The shallow seaway closed several million years before it otherwise likely would have due to these specific processes — mantle convection and corresponding changes in dynamic topography,” said Straume, who now works for Norway’s NORCE research center. “Without the plume, you could argue that the continental collision would have been different.”

Wildlife Migration Transforms Ecosystems

For millions of years, Africa existed as an isolated continent with unique animals evolving without outside influences. When the land bridge – named after Gomphotherium, an elephant-like creature that crossed it – formed around 20 million years ago, it began what scientists call the Great Old World Biotic Interchange.

African mammals, including elephant ancestors, moved into Eurasia, while Eurasian species expanded south into Africa. This exchange transformed ecosystems across both continents. Monkey-like primates had previously moved from Asia to Africa during an earlier period, and their African descendants later returned to Asia during this migration event.

In this case, timing is everything. If the land bridge had formed a million years later, the animals that migrated between continents could have been on different evolutionary paths. That includes human ancestors.

“It’s an example of how the long-term convective evolution of the planet talks to the evolution of life,” Straume said.

Ocean Currents and Climate Transformation

The research team, with scientists from six countries, used computer models to reconstruct how the changing landscape affected ocean circulation and climate.

Before the seaway closed, warm surface waters flowed from the Indo-Pacific into the Atlantic, while deep, salty water moved the opposite way. The closure strengthened the Atlantic Meridional Overturning Circulation – the ocean conveyor belt that moves warm water northward in the Atlantic and returns cold water southward at depth. This circulation pattern remains fundamental to our current climate system.

“The closure of the Neotethys was a necessary domino to fall for the transition from a global circulation mode dominated by Southern Ocean Deep Water to one dominated by North Atlantic Deep Water,” the researchers note.

The closure created contrasting regional effects on land. North Africa became drier as Atlantic moisture was blocked, potentially contributing to the Sahara Desert’s formation. Meanwhile, South Asia grew wetter as the newly raised land enhanced monsoon patterns.

This uplift of the Arabian Peninsula had significant impacts on ocean circulation and Earth’s climate. Nearby ocean temperatures warmed, which widened seasonal temperature ranges and made areas from North Africa to Central Asia more arid. Researchers believe this land bridge was a final trigger in making the Sahara a desert, while these topographical changes enhanced monsoon seasons in Asia, making Southeast Asia wetter.

Understanding this ancient event provides context for today’s climate challenges. The gradual cooling trend initiated by these changes over millions of years has rapidly reversed due to human-caused warming – occurring at a pace far exceeding any natural climate shift in Earth’s recent history.

By showing how processes deep within Earth transformed climate and wildlife, this research reveals the intricate connections between Earth’s different systems – from the hot interior to ocean currents to animal migrations – and demonstrates how dramatically our planet can change even without human intervention.