A new study shows that you can learn much from analyzing a microscopic drop of ancient seawater. Researchers have analyzed a series of such drops and arrived at an estimate that the process that underpins Earth’s plate tectonics may have started some 600 million years earlier than previously thought.
By analyzing levels of H2O and other molecules in microscopic “melt inclusions” caught in volcanic rock samples known as komatiites, researchers have come up with a new timeline for when seawater started getting pushed down from the surface into the mantle – the point when convection started occurring in Earth’s mantle.
The team was able to analyze the ancient water droplets after they had been captured by the mineral olivine, found in komatiites from the Komatiite lava flow.
“The mechanism which caused the crust to sink into the mantle functioned over 3.3 billion years ago,” says geologist Alexander Sobolev from the Russian Academy of Sciences.
“This means that a global cycle of matter, which underpins modern plate tectonics, was established within the first billion years of the Earth’s existence, and the excess water in the transition zone of the mantle came from the ancient ocean on the planet’s surface.”
The shifting of Earth’s plates and mantle has an effect on everything from atmospheric conditions to the minerals deposited underground, as well as the earthquakes and volcanoes associated with tectonics.
“Plate tectonics constantly recycle the planet’s matter, and without it the planet would look like Mars. Our research showing that plate tectonics started 3.3 billion years ago.
“says geoscientist Allan Wilson, from Wits University in South Africa. The geological landscape formed by these tectonic movements also provides an excellent record of what has happened in the past, which the researchers have tapped into here.