A new study with emerging evidence suggests that plate tectonics, or the recycling process of Earth’s crust, may have begun much earlier than previously thought – potentially a key reason why our planet supports life. This research is considered groundbreaking and may decode some of Earth’s deepest mysteries.
Plate Tectonics
Plate tectonics may play a larger role in the evolution of life on Earth than we previously thought. (Photo: Nicholas Forder).
The surface of the Earth is a chaotic place. Mountains rise, continents merge and break apart, and earthquakes shake the ground. All these processes are the result of plate tectonics, the movement of massive blocks of Earth’s crust.
This movement could explain why life exists. Earth is the only known planet with plate tectonics and the only one known to support life. Most scientists believe that this is not a coincidence.
By pulling these giant crustal blocks into the mantle, the Earth’s middle layer, plate tectonics draws carbon from the surface and atmosphere, stabilizing the climate. It also pushes minerals and molecules that nourish life to the surface. All these factors combine to create a place where life thrives, from the depths of the ocean to the highest mountain peaks.
However, researchers do not know why or when plate tectonics began, making it difficult to determine how crucial this process is for the evolution and diversification of life. Some suggest that tectonic movement started around 700 million years ago when simple multicellular life already existed. Others believe that only single-celled organisms dominated when Earth’s plates first began to separate.
In fact, as new methods allow scientists to look deeper into the past, some argue that plate tectonics appeared very early after Earth formed – perhaps even before life itself. If this hypothesis is correct, it could suggest that even the most primitive life evolved on an active planet – indicating that plate tectonics may be an essential component in the search for extraterrestrial life.
Diverse Tectonic Plates
At Thingvellir National Park in Iceland, the crack between the North American and Eurasian tectonic plates is clearly visible. (Photo: Mlenny)
Only Earth has tectonic plates that collide and separate like bumper cars. Other rocky planets in the Solar System have a single, rigid crust – a geological arrangement that scientists refer to as “stagnant lid” or “single lid.”
In a geological balancing act, the dense oceanic crust is destroyed at subduction zones, where one plate slides beneath another. The oldest known piece of oceanic crust, located in the Mediterranean, dates back only 340 million years, making it too young to be useful for accurately determining when plate tectonics emerged.
The continental crust is lighter than the oceanic crust and floats above the destruction caused by subduction. However, very little remains from Earth’s early days, and what remains has been eroded and warped. Less than 7% of the rocks on the surface today are over 2.5 billion years old. Going back to more than 4.03 billion years ago, to the Hadean era, and the rock record has completely vanished. The first half billion years of life on Earth left behind no trace of basalt.
Due to the planet’s continuous recycling process, the oldest undeniable evidence of plate tectonics – rocks formed only in subduction zones – dates back only about 700 million years.
Geologists agree that whenever tectonics began, it may have driven the evolution and complexity of life.
In prehistoric animals, tectonic activity is linked to faster evolutionary rates, possibly due to geological movements that divided habitats and created new niches for life to evolve.
Plate tectonics may have also helped life recover after devastating mass extinctions. For example, at the end of the Permian period, a mass extinction caused by volcanic eruptions releasing carbon dioxide killed 90% of species on Earth.
Life on the planet eventually recovered because the weathering of continental rocks broke down carbon-containing minerals and washed them into the oceans, where marine organisms transformed them into coral reefs and shells, which became limestone and eventually sank back into the planet. As the atmosphere became chaotic, tectonics gradually returned Earth to a more favorable environment for life.
Life on Other Worlds
If plate tectonics drives life, the search for other beings among the stars could lead humanity to a planet with strong geological activity.
Unfortunately, we have yet to detect plate tectonics on distant exoplanets, said Tobias Meier, a mantle dynamics expert at the University of Oxford. However, in 2021, Meier and his team used thermal data and computer models to determine that the rocky exoplanet LHS 3844 b, located 49 light-years from Earth, may have an active mantle and moving crust.
LHS 3844 b is unlikely to contain life and has no atmosphere. One half of the planet is always in daylight, with temperatures reaching 767 degrees Celsius, while the other half plunges to minus 273 degrees Celsius at night. It is this temperature difference between the two sides of the planet that drives the mantle movement on LHS 3844 b, Meier and his colleagues reported in 2021. If true, that version of plate tectonics is unlike Earth’s. But it suggests that the diversity of planetary geology may lurk elsewhere in the universe.
