New theory on how Earth's crust was created

May 5, 2017
A composite image of the Western hemisphere of the Earth. Credit: NASA

More than 90% of Earth's continental crust is made up of silica-rich minerals, such as feldspar and quartz. But where did this silica-enriched material come from? And could it provide a clue in the search for life on other planets?

Conventional theory holds that all of the early Earth's crustal ingredients were formed by volcanic activity. Now, however, McGill University scientists Don Baker and Kassandra Sofonio have published a theory with a novel twist: some of the chemical components of this material settled onto Earth's early surface from the steamy atmosphere that prevailed at the time.

First, a bit of ancient geochemical history: Scientists believe that a Mars-sized planetoid plowed into the proto-Earth around 4.5 billion years ago, melting the Earth and turning it into an ocean of magma. In the wake of that impact—which also created enough debris to form the moon—the Earth's surface gradually cooled until it was more or less solid. Baker's new theory, like the conventional one, is based on that premise.

The atmosphere following that collision, however, consisted of high-temperature steam that dissolved rocks on the Earth's immediate surface—"much like how sugar is dissolved in coffee," Baker explains. This is where the new wrinkle comes in. "These dissolved minerals rose to the upper atmosphere and cooled off, and then these silicate that were dissolved at the surface would start to separate out and fall back to Earth in what we call a silicate rain."

To test this theory, Baker and co-author Kassandra Sofonio, a McGill undergraduate research assistant, spent months developing a series of laboratory experiments designed to mimic the steamy conditions on early Earth. A mixture of bulk silicate earth materials and water was melted in air at 1,550 degrees Celsius, then ground to a powder. Small amounts of the powder, along with water, were then enclosed in gold palladium capsules, placed in a pressure vessel and heated to about 727 degrees Celsius and 100 times Earth's surface pressure to simulate conditions in the Earth's atmosphere about 1 million years after the moon-forming impact. After each experiment, samples were rapidly quenched and the material that had been dissolved in the high temperature steam analyzed.

The experiments were guided by other scientists' previous experiments on rock-water interactions at high pressures, and by the McGill team's own preliminary calculations, Baker notes. Even so, "we were surprised by the similarity of the dissolved silicate material produced by the experiments" to that found in the Earth's crust.

Their resulting paper, published in the journal Earth and Planetary Science Letters, posits a new theory of "aerial metasomatism"—a term coined by Sofonio to describe the process by which silica minerals condensed and fell back to earth over about a million years, producing some of the earliest rock specimens known today.

"Our experiment shows the chemistry of this process," and could provide scientists with important clues as to which exoplanets might have the capacity to harbor life Baker says.

"This time in early Earth's history is still really exciting," he adds. "A lot of people think that life started very soon after these events that we're talking about. This is setting up the stages for the Earth being ready to support life."

Explore further: Video: Earth as a planet

More information: Don R. Baker et al, A metasomatic mechanism for the formation of Earth's earliest evolved crust, Earth and Planetary Science Letters (2017). DOI: 10.1016/j.epsl.2017.01.022

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12 comments

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ursiny33
1.4 / 5 (10) May 05, 2017
The moon of earth is a mars sized object
RealScience
4.6 / 5 (11) May 05, 2017
The moon of earth is a mars sized object


Earth's moon is only ~10% of the mass of Mars.
StudentofSpiritualTeaching
1.7 / 5 (11) May 06, 2017
A pity that so much research is still conducted on a false premise about our moon's origin.
FredJose
1.7 / 5 (12) May 06, 2017
First, a bit of ancient geochemical history: Scientists believe that a Mars-sized planetoid plowed into the proto-Earth around 4.5 billion years ago, melting the Earth and turning it into an ocean of magma.

This is just philosophical story telling. There is no science in this. There is no supporting evidence that this was the case. There is no observational record that it actually occurred as speculated, so anything else based on this story is just more speculation and so much hot air.

One needs to be careful when listening to these stories and not be taken in by them. They are not even close to being anything in the realm of science.
FredJose
1.4 / 5 (11) May 06, 2017
As for their findings, it's not connected to anything that happened in the past, it's simply pure speculation that is now seemingly finding some "scientific" support.

If one were to go to the only eye-witness account of our origins it would be much clearer as to how the solid part of earth could have arisen. The earth was once fully covered by water. Then the land was made to rise up and some of the water caused to sink down. One can speculate that the cause of the land rising up might have been some kind of volcanic activity or even perhaps the actual transmutation of water into the various elements that make up the crust of the earth. This might have given rise to exactly the same kind of real life observation that the researchers have made. So in exactly the same way that their so-so story is not science and never can be, so is mine. Our origin occurred once and is unlikely to be repeated unless we develop technology to such an extend that we can go about forming our own planets.
zz5555
4.3 / 5 (6) May 06, 2017
One needs to be careful when listening to these stories and not be taken in by them. They are not even close to being anything in the realm of science.

I'm not sure, but this suggests very strongly that Fred is a Poe. It doesn't seem possible that anyone could be so lacking in self-awareness as to post something this unintentionally ironic.
Dingbone
May 06, 2017
This comment has been removed by a moderator.
Bart_A
1 / 5 (6) May 07, 2017
I would not call this a theory. Not even a hypothesis.
According to an online dictionary,

A hypothesis is either a suggested explanation for an observable phenomenon, or a reasoned prediction of a possible causal correlation among multiple phenomena. In science, a theory is a tested, well-substantiated, unifying explanation for a set of verified, proven factors. A theory is always backed by evidence; a hypothesis is only a suggested possible outcome, and is testable and falsifiable.

I would call it simply fantasy.

TheGhostofOtto1923
4.1 / 5 (9) May 07, 2017
This is just philosophical story telling. There is no science in this. There is no supporting evidence that this was the case. There is no observational record that it actually occurred as speculated, so anything else based on this story is just more speculation and so much hot air
-Nor is there any science in your favorite premise that the celestial bodies were all conjured up in a day.

Like I say, that unscientific premise of yours leaves everything you say in doubt.

Re the article I was always fascinated how hydrothermal vents could dissolve silicates like sugar and carry them to the surface where they form nice crystals. Interesting that this could happen across the surface of a planet, and entirely plausible.
katesisco
1 / 5 (5) May 07, 2017
Well, such shilly-shallying is to be expected when so much back-tracking is required.
Sounds like a plasma arc contacting Earth to create so much damage and we do have evidence of that on Mars and here if you believe the Electric Universe folks.
I suspect we are inching ever-so-slowly to W Brown's hydroplate theory InTheBeginning. That awesome shelling of granite over the MOHO would be an amazing admission. Dr Brown has hid his theory in creationism for decades but his MIT degree was based on it. He was experimenting with the results of cavitation which at that time was a big military problem for future submarine warfare.
Do you think it is possible to create granite from water?
TheGhostofOtto1923
4 / 5 (8) May 07, 2017
Do you think it is possible to create granite from water?
Do you think it is possible to create wine from water?
rrwillsj
1 / 5 (1) May 08, 2017
Gotta feel sorry for these crackpot commentators.

Their 'whine' comes from drinking dehydrated water...

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