Scientists have found out what the first continents of the Earth could have originated from

Scientists have studied ancient granite rocks from the North China Craton, one of the oldest fragments of the Earth's crust. These rocks date back to the Archaean, a very ancient period of Earth's history when the planet looked very different: the atmosphere was almost oxygen-free and the surface was covered with oceans, volcanic islands and young crust.

Details

The researchers focused on TTG-type rocks - tonalites, trondhyemites and granodiorites. These are the kinds of rocks that made up a significant portion of Earth's early continental crust. For a long time, scientists have debated whether they were formed from fresh deep rocks of the mantle or from already altered surface rocks.

To test this, the authors analysed sulphur and silicon isotopes in ancient granites about 2.7-2.5 billion years old. These isotopes work like chemical "fingerprints": they can show whether material has travelled across the Earth's surface and come into contact with the ocean and atmosphere.

The results showed unusual sulphur anomalies and a "heavier" isotopic composition of silicon. Such features are difficult to explain by the melting of fresh matter from the mantle alone. They fit much better with a scenario in which surface rocks - altered oceanic crust and sediments - were involved in the formation of ancient granites.

Simply put, the first continents may have been partially "assembled" from material that had already been on the Earth's surface, been altered by water and atmosphere, and then reappeared in the planet's depths.

Why it matters

The study changes the way we think about the early Earth. It shows that reworking of the Earth's crust may have started a very long time ago - perhaps as early as more than 3.8bn years ago.

This doesn't necessarily mean that the early Earth already had modern plate tectonics in its usual form. But the evidence suggests that the planet's surface, ocean, atmosphere and interior were connected much earlier than imagined.

This connection may have been important for the formation of continents and conditions suitable for life. If surface rocks went deeper, melted and became part of the crust again, it meant that the Earth was already then a dynamic system where matter was constantly being moved and recycled.

Background

The Archaea is one of the earliest stages of Earth's history. It began about 4 billion years ago and ended about 2.5 billion years ago. It was during this time that the oldest parts of the continental crust were forming.

Continental crust is different from oceanic crust: it is lighter, thicker and able to persist for billions of years. So the question of how the first continents appeared is directly related to how Earth became a planet with stable land, oceans, and long-term conditions for life.

The new study adds an important detail: the early continents may not have been simply the product of deep magmatic processes, but the result of a complex cycle involving the ancient ocean, atmosphere and recycled crust.

Source

The study by Kun Shang and co-authors Coupled sulfur-silicon isotopes reveal supracrustal origin of Archean continents is published in Nature Communications in 2026. The authors studied sulfur and silicon isotopes in ancient granitic rocks of the North China Craton and concluded that a significant part of the Archean continental crust could have formed from reworked surface rocks.