How did the tectonic plates of the earth form? You would think that this would be an easy question to answer, given that we are now trying to pinpoint the details of when it has happened and whether there is tectonic activity on the moon. But our knowledge of how this planetary mechanism came about is surprisingly low.
Researchers from China, Hong Kong and the United States have now put forward a new hypothesis – one that at first glance looks incredibly similar to an idea that was discredited decades ago, but now deserves a revision.
Tectonic plates shuffled around the surface of our planet 3.3 to 4.4 billion years ago, depending on who you ask. But a few billion years of tectonic movement and crust recycling have made it quite difficult to figure out how the earth got tectonic plates at all.
A few years ago, the researchers developed a model that shows that tectonic plates first formed in a process similar to how they shifted further ̵
However, the new research presents a model that shows something completely different. The research team suggests that the recently formed earth shell became hot billions of years ago, causing the shell to expand and rupture, leading to what we know today as tectonic plates.
“We use 3D spherical shell models here,” the team writes in their new work, “to demonstrate a self-organized fracture mechanism that is analogous to the lithospheric buoyancy driven by thermal expansion.”
Over: A snapshot of the model shows late stages of growth and fusion into the plate tectonic earth. Fractures are black and colors show tension.
Now the expanding earth hypothesis is not a new idea. In the 1800s, an expanding earth was proposed to explain how geographical features like mountains could have formed; However, it was discredited when we discovered plate tectonics.
However, the new scenario is not quite the same as that in Charles Darwin’s time. The key difference is where the earth blew off steam all those years ago.
“The answer lies in taking into account the major heat loss mechanisms that may have occurred in the early periods of the earth,” said Hong Kong University planetary scientist Alexander Webb.
“If volcanic advection, which transports hot material from the depths to the surface, was the main cause of the early heat loss, it all changes.”
It boils down to whether the earth’s heat loss through heat conduction (which radiates evenly over the planet) has occurred over a long period of time, or whether volcanoes spewed lava (and heat) from inside the planet to the surface where it cooled.
This accumulation of chilled material would have finally sunk and cooled the lithosphere and slowed the volcanoes along with the overall cooling of the earth. This in turn would have trapped the planet’s internal heat, which expanded the crust and caused it to break and form tectonic plates.
“Our numerical experiments show that the polygon cracks on the surface of the earth can develop as a by-product of the fracture in response to flat lithospheric processes with triple transitions,” the team writes in his work.
“The rapid development of the fracture network in each experiment takes place with a total expansion of about 1 km and takes ~ 5 million years.”
It is important to note that this study is only a hypothesis. We are still a long way from understanding what happened on ancient Earth and resulted in tectonic plates. With more evidence, this hypothesis could be an important part of developing the unique features of our planet.
The research was published in Nature communication.