There wasn’t plate tectonics when life first thought to originate on Earth: Study

Plate tectonics, the movement and interaction of large plates on Earth's surface, plays a crucial role in shaping the planet and creating the geological features necessary for the development of life. It allows heat from Earth's interior to escape to the surface, leading to the formation of continents and other vital elements. However, until now, little was known about plate tectonics during Earth's initial years.

By examining tiny mineral crystals known as zircons, researchers have gained unprecedented insights into plate tectonics billions of years ago, shedding light on the conditions that existed during Earth's infancy and the emergence of life. The findings indicate that mobile plate tectonics, thought to be necessary for the creation of a habitable planet, was not occurring on Earth 3.9 billion years ago. Instead, Earth was releasing heat through a stagnant lid regime.

"We found there wasn't plate tectonics when life is first thought to originate, and that there wasn't plate tectonics for hundreds of millions of years after. Our data suggests that when we're looking for exoplanets that harbor life, the planets do not necessarily need to have plate tectonics," says John Tarduno, who teaches in the Department of Earth and Environmental Sciences at the University of Rochester.

Tarduno, the William R. Kenan, Jr. Professor, is the lead author of a paper published in the science journal Nature examining plate tectonics from a time 3.9 billion years ago. This groundbreaking study, funded by the US National Science Foundation, involved researchers from prestigious institutions in the United States, Canada, Japan, South Africa, and the United Kingdom.

By dating zircons, tiny crystals containing magnetic particles that can retain the magnetization of Earth at the time of their formation, researchers can construct a timeline tracing the evolution of Earth's magnetic field. The magnetic properties of zircons provide insights into the relative latitudes at which they formed, as the strength and direction of Earth's magnetic field vary depending on latitude.

Contrary to their expectations, Tarduno and his team found that the zircons from South Africa indicated a stable magnetic field strength between 3.9 and 3.4 billion years ago. This stability implies that the latitudes of Earth during this period did not undergo significant changes. Tarduno suggests that this lack of latitude variation suggests that plate tectonic motions were not occurring at the time and that alternative mechanisms were responsible for dissipating heat from Earth.

The researchers confirmed the same patterns when studying zircons from Western Australia, further supporting their findings. While plate tectonics is considered Earth's primary heat release mechanism, the discovery of stagnant lid tectonics challenges the prevailing notion. Stagnant lid tectonics involves the cracking of Earth's outer layer, allowing heat to escape from the interior and form continents, albeit less efficiently than plate tectonics.

Notably, Earth is the only known planet to experience plate tectonics, while other planets like Venus undergo stagnant lid tectonics. The study's findings suggest that plate tectonics might not be a requirement for life to originate on a habitable planet.

"We think plate tectonics, in the long run, is important for removing heat, generating the magnetic field, and keeping things habitable on our planet. But, in the beginning, and a billion years after, our data indicates that we didn't need plate tectonics," Tarduno says.