1.5 billion-year-old Earth was a 'Waterworld'

New evidence suggests that 1.5 billion years ago, the planet was covered by a vast ocean and had no continents.

    2020/03/06

NSFW    BOULDER, COLORADO — New evidence from Iowa State University and the University of Colorado suggests that 1.5 billion years ago, the planet was covered by a vast ocean and had no continents.

Published in Nature Geoscience, the research examined more than 100 ancient samples of seafloor, located now in the outback of northwestern Australia. Its rocky scenery of craggy seafloor preserves a hydrothermal system dating back 3.2 billion years.

Lead study author, Benjamin Johnson told Live Science that when the Earth was 1.5 billion years old, the ocean had high levels of isotope oxygen-18.

Their computer models showed that continental landmasses leach oxygen-18 from the oceans, but in the ancient samples, he observed an abundance of it.

So, in the absence of continents, the oceans would carry more oxygen-18, which implies a "Waterworld."

The continents appeared later, as plate tectonics drove enormous, rocky landmasses upward to breach the sea surfaces.

The prospect of an ancient Waterworld Earth also offers a new perspective on another intriguing question: where the planet's earliest forms of life appeared and how they evolved.

Questions the team hopes to answer.
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