This provided us with the opportunity for life to emerge. That is what happened to the ancient Earth, as shown by a groundbreaking study led by geodynamics expert Zheng Xiang Li from Curtin University (Australia).
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3.2 billion years ago Earth – Graphic from LIVE SCIENCE.
In 2020, Li’s team reported changes in the chemical composition of rocks formed in Earth’s crust 3.2 billion years ago, suggesting that a planetary-scale mixing event had occurred. Recently, in a publication on Science Direct, they revealed evidence for this through “treasure” excavated in lead-zinc mines in Australia.
The U-Th-Pb system, which refers to the isotopic systems of uranium, thorium, and lead, is one of the most widely recognized “geological clocks” used by scientists.
The mines in Australia helped them determine that our planet was “stirred up” during that period, altering the isotope ratios that no longer matched the materials found in primitive solar system bodies, such as carbonaceous chondrites, which we occasionally discover.
All of this recounts an extremely crucial milestone of Earth: from a solid, tranquil sphere like Venus or Mars, it began to undergo tectonic activity around 3.2 billion years ago when the planet was only 1.3 billion years old.
Plunging into this “limit point,” the primitive tectonic activity violently mixed the materials on and within the Earth.
Today, Earth continues to experience tectonic activity. The planet’s crust is actually composed of nearly 20 small to large pieces that are continuously moving, carrying oceans or continents on each piece. This is why in the planet’s history, continents have repeatedly come together to form supercontinents and then break apart, just as they do now.
This process of plate tectonics is incredibly significant for us, as it provides the driving force for biochemical reactions that give rise to primitive life, as well as maintaining a planet with an atmosphere, hydrosphere, and stable environment for life to thrive and evolve.
The milestone that Australian scientists have found – 3.2 billion years – also aligns with some evidence of the time when primitive life actually appeared in the form of living organisms.
Thus, it can be said that scientists have uncovered an extremely significant “lost chapter” of the planet’s history.