Earth's primordial water cycle was key to making continents, study shows

Credit: Curtin University

A new study from Curtin University has found that water was transported much deeper in the early Earth than previously thought, explaining how the continents originally formed.

Studies published in Earth and Planetary Science Letteranswers a long-standing question about Earth’s early water cycle.

Principal investigator Dr. Michael Hartnady, of the Curtin School of Earth and Planetary Sciences, says how water is stored and transported through the Earth’s crust affects everything from where volcanoes and mineral deposits form to where earthquakes occur.

“Although we understand the modern deep water cycle, we know very little about how it worked when Earth was a very young planet,” said Dr. Hartnady.

“Some geological evidence suggests that water was transported to great depths on Earth all the way back to 3.5 billion years ago, although it is not well understood how exactly it got there.”

The researchers used advanced modeling to show that primitive high-magnesium volcanic rock — which erupted into the seafloor early on Earth — would have absorbed more seawater than more modern lava.

“This water, which is locked into certain crystals within the rock, gets released when the rock is buried and begins to ‘sweat.’ In modern lava, this sweat occurs at temperatures around 500 degrees Celsius,” said Dr Hartnady.

“Our findings suggest that most of the seawater that was originally bound within ancient primitive lavas would have been released at much higher temperatures, greater than 700 degrees Celsius.

“Importantly, this means that water was transported much deeper into the early Earth than previously thought. Its release would have caused the surrounding rock to melt, eventually forming continents.”

Dr Hartnady said the research helped explain how the planet’s interior worked more than 2.5 billion years ago.

“Interestingly, the oldest parts of the continent, the cratons, also contain some of the largest gold deposits on Earth including the Golden Mile near Kalgoorlie,” said Dr. Hartnady.

“These gold deposits required large amounts of water to form, and we still don’t have a good explanation of where they came from. Our new research could help solve this and other questions, perhaps even related to the origin of life.”

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New clearer insights into hidden crystals on Earth

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Further information:
Michael IH Hartnady et al, Early Earth fluid processes and continental growth, Earth and Planetary Science Letter (2022). DOI: 10.1016/j.epsl.2022.117695

Provided by Curtin Universitas University

Quote: Earth’s primordial water cycle was key to making continents, study shows (2022, 27 July) retrieved 27 July 2022 from https://phys.org/news/2022-07-earth-ancient-key-continents.html

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