Privileged Planet: early Earth a water world (Introduction)

by David Turell , Tuesday, March 03, 2020, 20:21 (1505 days ago) @ David Turell

New research suggests the early Earth ws totally covered with water:

https://www.theguardian.com/science/2020/mar/02/earth-may-have-been-a-water-world-3bn-y...

"Scientists have found evidence that Earth was covered by a global ocean that turned the planet into a “water world” more than 3bn years ago.

"Telltale chemical signatures were spotted in an ancient chunk of ocean crust which point to a planet once devoid of continents, the largest landmasses on Earth.

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"Their work centred on a geological site called the Panorama district in north-western Australia’s outback, where a 3.2bn-year-old slab of ocean floor has been turned on its side. Locked inside the ancient crust are chemical clues about the seawater that covered Earth at the time.

"The scientists focused on different types of oxygen that seawater had carried into the crust. In particular, they analysed the relative amounts of two isotopes, oxygen-16 and the ever-so-slightly-heavier oxygen-18, in more than 100 samples of the stone.

"They found that seawater contained more oxygen-18 when the crust was formed 3.2bn years ago. The most likely explanation, they believe, is that Earth had no continents at the time, because when these form, the clays they contain absorb the ocean’s heavy oxygen isotopes.

“'Without continents above the ocean, the oxygen value would be distinct from today, which is exactly what we found,” Johnson said. “And it’s different in a way that’s most easily explained without land to get rained on and without soil formation.”

"The findings do not mean Earth was entirely landless at the time. The scientists suspect that small “microcontinents” may have poked out of the ocean here and there. But they do not think the planet hosted vast soil-rich continents like those that dominate Earth today."

Comment: An interesting aspect of the history of our early Earth