Geologists have developed a new theory of the state of the Earth billions of years ago, after studying the very old rocks that formed in the Earth’s crust beneath the continents.
Balz Kamber, a professor at Trinity College Dublin and Queensland University of Technology, and Assistant Professor Emma Tomlinson recently published their research in a leading international journal. Nature communications,
Today, the seven continents on Earth are each built on a stable inner part called a craton. Geologists believe that the stabilization of a craton about 2.5 to 3 billion years ago was important for the formation of terrestrial masses on Earth.
Little is known about the formation of cratons and their auxiliary coverings, but traces can be found in peridotite xenoliths, which are fur specimens brought to Earth by volcanic eruptions.
Dr. Tomlinson of the Trinity School of Natural Sciences said:
“Many rocks from the mantle under the old continents contain a surprising amount of silica, much more than is found in the younger parts of the mantle.”
“There is currently no scientific consensus on why.”
New research examining global data on peridotitis comes with a new explanation for this observation.
The study used a new thermodynamic model to calculate that unusual mineralogy developed when very hot molten rocks above 1700 ° C interacted with older parts of the mantle, causing silicon-rich minerals to grow.
“More than 1 billion years ago, 3.8 to 2.5 billion years ago, volcanoes erupted – very unusual very low viscosity lava – lava that was very thin, very hot, often containing variable levels of silica,” added Dr. Tomlinson.
“Our modeling suggests that the unusual lavas were actually molten rock that interacted with the mantle at great depth, resulting in a variable level of silicon.”
Professor Kamber, QUT, said:
“And the silicon-rich rocks in the deep mantle, the low-viscosity volcanic rocks, stopped producing the Earth about 2.5 billion years ago. This time is the boundary between the ancient “Proterozoic eras”, one of the most significant breaks in the Earth’s geological calendar.
It is unknown at this time what he will do after leaving the post.
Professor Kamber added:
“It may be due to a change in the flow of the mantle. “When the cloak began to turn slowly to the core (2,900 km), the very high temperatures of ancient times were impossible.”
Reference. February 17, 2021 Nature communications,
DOI: 10.1038 / s41467-021-21343-9: