[Rockhounds] Greenland's Rocks Contain Hints of a Magma Ocean on Baby Earth

[Kreigh Tomaszewski]

Billions of years ago, parts of Greenland were a molten sea, a sharp
contrast to the pale-blue ice seen there today. Researchers have now found
isotope signatures of that burbling, primordial Earth in basalt rocks near
Nuuk.

It’s generally accepted that early in its history, Earth had a big magma
ocean; it’s a common step in the early evolution of planets. But thanks to
the planet’s tectonics, little evidence remains of what that version of
Earth looked like.

The research, published <http://dx.doi.org/10.1126/sciadv.abc7394> today in
the journal Science Advances, describes iron and tungsten isotope
signatures from 3.7-billion-year-old rock that are indicative of elements
of Earth’s mantle in the first half-billion years of our planet’s formation.

“The driving question that motivated me was, if we think the magma ocean
stage was important to the Earth’s history, why is there no geological
evidence for it?” said Helen Williams, a geologist at the University of
Cambridge and lead author of the paper, in a video call. “What if we
actually tried to directly hunt for it?*”*

Earth is constantly cleaning the tectonic slate with its geological
activity; the site in Greenland is the first to indicate such a giant,
fiery sea. In fact, the research site at Isua is the same outcrop that
caused a buzz a few years back when possible stromatolites—fossils of
bacteria, the earliest known life on Earth—were identified there. The
magmatic activity recorded in the rocks would’ve occurred hundreds of
millions of years before such microbes ever set up shop, though, when Earth
and the Moon had only recently become distinct objects. (In fact, it’s
easier to find information about the magma ocean by looking on the Moon
<https://gizmodo.com/chinas-lunar-mission-has-found-mantle-material-on-the-f-1834783996>.)
When
the magma ocean finally cooled, some of its deeper components crystallized
at very high pressures over 400 miles beneath Earth’s surface, Williams
said.

https://gizmodo.com/greenlands-rocks-contain-hints-of-a-magma-ocean-on-baby-1846466000