Ancient Rocks Reveal Origins of Earth's Earliest Crust and Continent Formation

How did Earth's first continents form? That's exactly what Jesse Reimink has been trying to find out. The University of Alberta geochemistry student has spent three years collecting and examining ancient rock samples of the earliest crust in order to understand how they formed, which could tell him how our planet changes through the years.

Today, continents form when one tectonic plate shifts beneath another into Earth's mantle. This causes magma to rise to the surface in a process called subduction. Yet it's unclear whether plate tectonics existed 2.5 billion to four billion years ago, or if another process is to blame.

"The timing and mode of continental crust formation throughout Earth's history is a controversial topic in early Earth sciences," said Reimink in a news release.

One theory holds that the first continents formed in the ocean as liquid magma rose from Earth's mantle before cooling and solidifying into crust. In fact, Iceland's crust formed when magma from the mantle rose to shallow levels, incorporating previously formed volcanic rocks.

But what is the actual answer? Scientists examined rock samples dated between 3.6 and four billion years old. Because of their extreme age, many of them had undergone multiple metamorphic events, which made it difficult to understand their geochemistry. Yet a few of them were better preserved.

In fact, the researchers found that the crust-forming processes of early Earth were very similar to those occurring in present-day Iceland.

"This provides the first physical evidence that a setting similar to modern Iceland was present on the early Earth," said Reimink in a news release.

The findings reveal a little bit more about our planet and how the continents formed. This, in turn, could inform future studies and tell us a bit more about the processes occurring on Earth today.

The findings are published in the journal Nature Geoscience.