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plate tectonics

Ancient water drops helps in calculating the timeline of plate tectonics of earth

Ancient water drops might have changed the timeline of the Earth’s tectonic plates as researchers have analyzed a series of drops from ancient seawater and arrived at an estimate that the process which underpins the plate tectonics of the Earth might have started 600 million years earlier than previously considered. The study has been published in Nature journal.

The constant movement of tectonic plates is a crucial part of renewing the surface of the planet and flourishing of life. By analyzing the levels of water in microscopic melt inclusions trapped in volcanic rock sample called komatiites, researchers calculated a new timeline when the seawater got pushed down from surface to the mantle, the point when convection started to occur. The ancient water droplets were captured in the mineral olivine found in the komatiites from the Komatiite lava flow which remained after the hottest magma was produced in Archaean Eon.

Geologist Alexander Sobolev from the Russian Academy of Sciences said the mechanism that caused the crust to sink into the mantle started 3.3 billion years ago. A global cycle of the matter was established within the first billion years and the excess water in mantle’s transition zone came from the ancient oceans.

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Factors like atmospheric conditions and minerals deposited underground have been affected by shifting of the Earth’s plates along with the earthquakes and volcanoes. The plate tectonics always recycles the matter on Earth without which our Earth would end up looking like Mars. Plate tectonics started 3.3 billion years before which coincides with the time life began on Earth.

The geological landscape which was formed by these tectonic movements provides an excellent record of what happened in the past. The komatiite was dug up from Weltevreden Formation in the Barberton greenstone belt in South Africa.

After examining the piece of melt of close to 10 microns and analyzing the chemical indicators like water content, chlorine and hydrogen/deuterium ratio, it was found that the Earth’s recycling process started close to 600 million years earlier than what was thought initially. It was found that the seawater was transported deep into the mantle and later re-emerged through volcanic plumes from the core-mantle boundary.

The chemical signature of the lithographic mantle matches with that of the analyzed rocks from the Archaean, despite coming from further down in the transition zone between upper and lower mantle. The komatiites grabbed so much water from deep underground before being shot up to the surface, which in turn indicates that the tectonics plate cycle happened earlier than 2.7 billion years ago which is the currently accepted starting point.  The chemical mixes, pressure, geological processes have many variations to account in the readings. More research is needed to figure out exactly when the material of the Earth’s crust started shifting.

Journal Reference: Nature

About the author: Kalpit Veerwal
Kalpit Veerwal is a second year Computer Science undergraduate at IIT Bombay. He is well known for being the only person to score 360/360 in JEE (Main). He is registered in the Limca Book of Records for the same. A blogger in his free time, he has also secured top ranks in various exams held in India and the world.

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