The researchers published a new study that found that the Earth’s continental crust appeared 500 million years earlier than previously believed. According to the team, the first appearance and persistence of the continental crust on Earth during the Archean between 4 billion and 2.5 billion years ago has implications for plate tectonics, ocean chemistry and biological evolution. The researchers note that the emergence of the continental crust occurred about half a billion years earlier than previously believed.
Scientists note that when the land is established through dynamic processes, such as tectonic plates, the earth begins to suffer from bad weather and add minerals and nutrients to the ocean. A record of these nutrients is preserved in ancient rocks. Previously, researchers used strontium isotopes in marine carbonates, but these rocks are generally scarce or altered when they are more than 3 billion years old.
The researchers have a new approach to tracking the first emergence of ancient rocks using a different mineral called barite. Barite is formed when sulfite from ocean water mixes with barium from hydrothermal vents. Barite keeps a record of the ocean’s chemistry in its structure, which is useful for reconstructing ancient environments. The project scientists took a piece of barite from the field that has been on Earth for 3.5 billion years, which is exactly the same as when it first precipitated.
The team tested six different deposits on three different continents, aged between 3.2 million and 3.5 billion years. The team calculated the proportion of strontium isotopes in the barite and was able to infer the time when the weathered continental rock made its way to the ocean and incorporated itself into the barite.
The team found that wear and tear began about 3.7 billion years ago, about 500 million years earlier than previously thought. The researchers say the discovery has implications for how we think about how life has evolved.