A new study revealed that the continental crust appeared for the first time on the surface of the earth about 3.7 billion years ago, that is, half a billion years ago than previously thought, and the first appearance of the continents also witnessed the beginning of weathering, a process that adds distinct minerals and nutrients to the ocean.
According to RT, a record of these minerals is kept in the ancient rock record, and geologists have traditionally looked at marine carbonates to study ancient weathering.
However, carbonates dating back more than 3 million years are rare and have typically changed since then through geological processes.
To get around this, geologists have now turned to a different mineral, barite, which is formed when sulfate in ocean waters interacts with barium from hydrothermal events.
It is noteworthy that the precise timing of the emergence of the continental crust during what is known as the abyssal era has implications for the history of plate tectonics, ocean chemistry, and the origins of life.
Study author Desiree Rordenck said, the composition of the barite piece that we picked up now, which has been on Earth for three and a half billion years, is exactly the same when it was actually deposited.
A geochemist from the University of Bergen, Norway said, in essence, it's really a wonderful recorder for looking at processes on early Earth.
In their study, Professor Rordenck and colleagues tested six different deposits of barite, located on three different continents, that ranged between 3.2 and 3.5 billion years old.
For each sediment, the team calculated the ratio of different isotopes of strontium present within the rock, from which they can infer the time when the changing continental rocks made their way into the ocean and ended up in barite.
Based on their results, the team concluded that the weathering of the continents first began about 3.7 billion years ago, 500 million years earlier than previously thought.
This is a huge time period.
Dr. Rordenck, explaining that while scientists usually believe that life began in the deep sea and in hydrothermal environments, the biosphere is complex. It has fundamental implications for the way we think about how life evolved. We do not really know if it is possible that life evolved at the same time on Earth, but then that earth must exist.
In addition, the researchers show that the early emergence of Earth may improve our understanding of plate tectonics and the Earth's dynamic origins.
Rordenck said, to get Earth, you need processes that work to form that continental crust and to form a crust that is chemically different from the oceanic crust.
The full results of the study will be presented at the 2021 EGU General Assembly, which takes place from April 19-30.