The Continents Rose Above Earth's Oceans Way Earlier Than We Thought

The Earth's thick continental crust -- the rocky stuff that makes up the land masses on which we live -- may have risen from the oceans much earlier in our planet's history than scientists thought.

Previous studies suggested that the crust surfaced within the past 2.5 billion years. But a new study indicates that they emerged some 500 million years earlier. Talk about old!

"There is increasing evidence from a number of studies that big changes were taking place at circa 3 billion years ago, and a number of people have argued that plate tectonics may have started at around that time," Dr. Bruno Dhuime, a geochemist at the University of Bristol in England and co-author of the study, told The Huffington Post in an email. "It is consistent that the continents emerged at that time."

For the study, the researchers scoured databases of previous analyses on more than 13,000 rock samples taken from the continental crust. In these analyses, the researchers took a close look at the chemistry and the ages of the rocks.

Based on that data, the researchers concluded that the chunks of crust must have emerged around 3 billion years ago -- and the buoyant nature of the rocks would have allowed them to rise high above what is now known as the oceanic crust (or seafloor), Live Science reported.

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A cross-section infographic of some of Earth's layers, depicting the continental crust (1), the oceanic crust (2), and the upper mantle (3).

Dhuime noted in the email that what happened in the time before the continental crust's debut remains a mystery.

"Before continents emerged we assume that much of the Earth was covered in basaltic crust, much like the crust we find at the bottom of the oceans today. It is still highly debated on how continents that were submerged in the oceans before 3 billion years ago formed," he said in the email. "We now intend to conduct further research on this highly debated topic."

The study was published online in the journal Nature Geoscience on June 22, 2015.

What lies beneath the continental crust? Check out the "Talk Nerdy To Me" episode below to take a wild journey inside Earth.