The great mystery of geology: When did tectonic plates form?

Although it is one of the most fundamental formation processes on Earth, The origin of plate tectonics is a controversial topic that could set fire to any meeting of geologists. Despite this, everyone agrees that the theory itself can provide a coherent structure; This not only gives us an explanation, but also but it also predicts the behavior of the Earth’s hard outer layer.

There is also a consensus that the exceptional character of the Earth’s tectonic system is one of the distinctive features that distinguish us from all (or almost all) known planets in the Universe.

But there are still some questions. When did the Earth’s surface divide into tectonic plates? So when did these plates start moving, colliding with each other, and diving into the planet’s interior? The answers to these questions vary greatly from 700 million years ago to 4 billion years ago, when our planet was in its infancy.

The oldest traces of plate tectonics

Interestingly, the newest theories place the development of plate tectonics at even earlier times. The research, published in June 2023 in the journal Nature, suggests that Earth developed its plate tectonics system 4.5 billion years ago during the Hadean period, our planet’s oldest geological period.

The research was conducted using zircons, defined as single-clastic crystals that, in addition to being precisely dated, “can provide constraints on lithospheric mobility spanning time scales of hundreds of millions of years.” Yale University professor Jun Korenaga states the following in an interview with LiveScience: theoretical modeling supports the existence of plate tectonics under Hadean conditions.

Studies of zircon and the chemistry of some of Earth’s oldest surviving rocks show that our newborn planet already exhibits some features similar to those of today, such as oceans and continental masses. This evidence contradicts the traditional view of a primitive Earth under extreme conditions, inhospitable and covered with magma.

Other theories regarding the beginning of plate tectonics

In addition to the early start theory, some geoscientists, such as Robert Stem of the University of Texas, argue that plate tectonics arose during the Neoproterozoic, between 1 billion and 541 million years ago. This time coincides with the emergence of ophiolites, in which pieces of oceanic crust are pushed up and incorporated into continental crust, he said in an interview with LiveScience.

The logic is simple: the existence of ophiolites and metamorphic rocks called blue shales suggests that they are both formed in subduction zones, that is, areas where one tectonic plate moves under another and then subducts into the Earth’s mantle. Since subduction is an indisputable feature of the existence of plate tectonics, this is concrete evidence that tectonic processes are already active..

However, many geologists oppose Sterm’s theory as conservative and argue that tectonics had an even later start because these plate rocks may have been destroyed or altered over time. “The Tibet-India collision is not over yet,” says Mark Harrison, professor emeritus of geology at the University of California, Los Angeles, but many of these “new” rocks have already been eroded.

Why is plate tectonics so difficult to date?

The organization’s biggest challenge An exact date for the beginning of plate tectonics is mainly due to the scarcity of very old rocks mentioned above.most were destroyed by later geological processes. Moreover, the process of interpreting billions of years of geological evidence is quite complex.

The evidence presented in these different theories each has a blind spot. For example, although zircons are thought to be accurate, most came from one place: the Jack Hills region of Australia, which may not be representative of the rest of the planet.

Because ancient rocks may not have gone through the same processes as new rocks, they may appear “strange” or different because they reflect conditions on the early Earth.

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