A new research suggests that long before the tectonic plates on the earth's surface, it was encased by a single shell. The egg-like deformable shell was the first covering that the earth had right after its formation and during the period of cooling down.
According to Mail Online, the research has suggested that the ancient earth's "single" crust eventually began to crack and fold, giving rise to tectonic plates. The frictional force of these plates lying side by side gave rise to earthquakes, volcanoes and other modern geological phenomena. This new study has been done from the University of Maryland, Curtin University in collaboration with Geological Survey of Western Australia. It has given the long-running debate about the earth's past a new outlook.
There have always been differences among researchers about whether the formation of plate tectonics started right after the formation of the earth, or the earth experienced a single shell-like covering while cooling off. The new research, though, supports the latter theory of the earth having a "stagnant lid" early in its history.
According to Phys.org, the researchers in their approach studied rocks of the oldest origin, almost 3.5 to 2.5 billion years ago. These were collected from Western Australia's East Pilbara Terrane. They also collected basalt rocks of "Coucal" formation, produced when the volcanoes erupt. The researchers performed thermodynamic calculations to understand the chemical composition of the basalt rocks. Using them and the Pilbara rocks, the researchers made a series of modeling experiments.
As the results suggest, the Pilbara rocks were granites formed by melting of the Coucal basalts or something similar in a "highly thermal gradient environment". The basalts also came from another generation of source rocks. This indicates that a multi- stage process produced earth's primary continents in a "stagnant lid" context prior to the plate tectonics.
The revealing of the chemical composition of the rocks during the research suggests that a single crust was first formed on the earth, which gave way to the rise of tectonic plates. The research results were published on February 27 in the journal "Nature".
