Earth -- the planet we're currently living in, breathing in, sleeping in, bathing in, and many other human activities you can think of doing -- was "born" about 4.54 billion years ago.

There's a lot we can and want to learn about early Earth's first billion year or gigayear, as well as its first 500 million years, or what some experts call the Hadean Eon.

This period was aptly named after the Greek god of the underworld Hades because scientists used to think that the early condition of the planet was literally "hell on Earth." They believed that early Earth was a barren wasteland covered with molten lava, and without an ocean or a solid crust.

Turns out, land masses and oceans may have been fully formed during the Hadean Eon, a past study revealed.

The Primordial Soup

In grade school, we're taught that early Earth was a "primordial soup" where life began to spring forth.

Our planet was only able to support life after it had cooled down enough for a rocky, but still shallow crust to solidify.

Water vapor from oceans and volcanoes condensed into the atmosphere, precipitated into rain, and collected on the surface of the planet.

A theory in 2014 suggested that space rocks may have bombarded the Earth during its early years, steamed the oceans, and caused water vapor to rise into the atmosphere.

Volcanoes also produced gases that were rich in the building blocks of life, namely hydrogen, carbon, nitrogen and oxygen. At this point, however, there was no free oxygen yet.

In that primordial soup of the early oceans, scientists say organic molecules formed more complex molecules that became simple cells. And because of the planet's distance to the sun, its geological history and its physical properties, life slowly began to emerge.

Diamonds Hold Clues To Primeval Earth

Now, scientists are obtaining more clues that reveal how ancient Earth might have worked.

Three diamonds dug up from ancient rock formations in Johannesburg during the early 19th century - before the industrialization of gold mining - were studied by a team of experts from the University of Alberta in Canada and the University of the Witwatersrand in South Africa.

Generously provided by Museum Africa, the diamonds were unearthed from the three-billion-year-old Witwatersrand Supergroup. This rock formation contains the famous gold mines in Johannesburg.

The research team used the diamonds to investigate when modern-style tectonic plates began to operate on Earth.

"Because diamonds are some of the hardest, most robust material on Earth, they are perfect little time capsules," said Dr. Katie Smart, lead researcher of the study and a lecturer at the Wits School of Geoscience. "And [they] have the capacity to tell us what processes were occurring extremely early in Earth's history."

Geoscientists have long been debating when tectonic plates started to operate on Earth. Many believe that that they began in the Archaean Eon which took place about four to 2.5 billion years ago. However, the timing is still highly contested.

The three diamonds were located in 3-billion-year-old sedimentary rocks, but the formation of diamonds within the Earth's mantle occurred much deeper.

Based on the three diamonds' nitrogen characteristics, scientists say they formed much earlier at about 3.5 billion years ago. The diamonds were transported to the surface of the planet by a small but powerful volcanic eruption caused by the quick ascent of kimberlites, an igneous rock. The diamonds then journeyed into the Witwatersrand Basin.

Investigating The Time Capsules

Through an ion probe, the research team analyzed the nitrogen and carbon isotope compositions of the three diamonds. Luckily, they have been pristinely preserved.

Smart and her colleagues discovered that tectonic plates were likely operating on Earth as early as 3.5 billion years ago.

How did they figure that out? Smart said they made use of the isotopes to find out where the source material involved in the formation of the diamonds came from.

The nitrogen isotopes pointed to a sedimentary source, which was nitrogen derived from the surface of the planet. Smart said this indicated that the diamonds did not originate from the mantle of the Earth, but were moved to the upper mantle through plate tectonics.

Thus, this meant that the nitrogen confined in the diamonds prove that plate tectonics was operating during the Archaean Eon.

"We are not the first research group to study diamonds in order to tell when plate tectonics began," said Smart. "But our study of confirmed Archaean diamonds has suggested that plate tectonics was in operation by at least 3.5 billion years."

The team's findings are featured in the journal Nature Geoscience.