Earth's crust took shape as plate tectonics started 4 billion years ago: study

The plate tectonics - which leads to splitting of the continents, creates mountains and leads to earthquakes - is likely to have started when Earth was very young, according to new research.

The new study states that plate tectonics began more than 4 billion years ago, which was not long before the planet got formed 4.5 billion years ago.

At this time, Earth was in the Hadean era when it was a fresh planet and very hot and had an ammonia-and-methane atmosphere. The atmosphere had enough water in it which later condensed into a planet-wide ocean.

In this era, Earth slowly cooled down and a solid outer crust was created. The crust was shaped by the tectonic plates' grinding movements.

Earlier, the researchers said that plate tectonics started in the Hadean, once the crust cooled down.

Meanwhile, others believed that plate tectonics began around 3.2 billion years ago when some key changes took place in the makeup of the crust, as revealed by geochemistry.

However, some argue that the phenomenon is recent and its modern form evolved in the last couple of billion years.

Here's how crystals helped determine when plate tectonics started

Scientists have faced difficulty in deciding when plate tectonics started since there are no surviving rocks which are more than 4 billion years old.

The only way to determine this is by analysing tiny, tough crystals known as zircon, which date back to 4.4 billion years.

A subset of these crystals, which are known as S-type zircons, can help in understanding plate tectonics.

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These zircons are crystals and are formed in sedimentary rocks on land. They are pushed by tectonics into the mantle and re-emerge like metamorphic granites.

In the latest research which was published in the journalPNAS, a machine-learning model was used by the researchers to understand these S-type zircons.

The data collected from 300 zircons was first fed by the scientists and then the ability of the model was tested to determine whether 74 more zircons were S-type or not.

In the results, it was found that 35 per cent of the Jack Hills zircons were S-type. A few of these were found dating back to 4.2 billion years ago. This hinted that plate tectonics was moving rocks from the crust to the mantle and again back to the crust during the Hadean.

(With inputs from agencies)