Earth’s crust and mantle grew in sync, study finds
The researchers said that this finding could help solve a fundamental mystery about our planet and also shed light on the formation of other planets
A new study led by Penn State researchers has challenged the prevailing theory that the Earth’s crust was formed rapidly about 3 billion years ago, and then slowed down its growth.
The study, published in Geochemical Perspectives Letters, suggests that the crust continued to evolve gradually for billions of years, in sync with the mantle layer below it.
The researchers said that this finding could help solve a fundamental mystery about our planet and also shed light on the formation of other planets.
Existing theory
According to the existing theory, the Earth was a stagnant lid planet with no tectonic activity until a sudden shift to tectonic plates 3 billion years ago. However, the new study shows that this is not the case, said Jesse Reimink, assistant professor of geosciences and lead author of the study.
To test this theory, the researchers used a large database of more than 600,000 samples of the Earth’s rock records, which have been analyzed by scientists across the world for their geochemical contents and age.
The researchers said that the rock record is more reliable than the mineral record, which was used to support the rapid formation theory because it is more sensitive and less biased on those time scales.
Image: nutnai / iStock
The researchers developed a novel method to estimate how much the igneous rocks in the database have been reworked and reformed over time by various processes, such as weathering, erosion, sedimentation, or remelting.
They used experimental data to show how the same rock could change in different ways over time and then applied mathematical tools to calculate the proportion of sediments in each rock sample.
Using this information, they calibrated the reworking rate in the rock record and then calculated the Earth’s crustal growth curve, which shows how much new crust was added over time. They compared this curve with the one derived from the mineral record by other experts.
Various crustal growth rate curves shown by dashed lines compared to the cratonic mantle age distribution. Vertical coloured arrows show the amount of continental recycling predicted by various estimates. The black curve shows the age distribution of unmodified cratonic mantle ages, while the green field shows the percentage of preserved mature sedimentary packages.
Image: Geochemical Perspectives Letters
The result was surprising: The crustal growth curve based on the rock record matched the mantle growth curve, indicating a correlation between the two layers. This contradicts the idea of a sudden change in crustal growth three billion years ago and supports a more gradual evolution of both crust and mantle.
Reimink said that this is not the first time that geoscientists have proposed a more gradual crustal growth scenario, but it is the first time that it has been backed up by the rock record.
He added that the study improves our understanding of how our planet formed and changed over time, but it is not conclusive. He said that there are still many gaps in the data and uncertainties in the methods.
He also said that further analysis of the existing data could help explore other planets, such as Venus, which has no tectonic plates and could resemble early Earth.
Reimink also raised an intriguing question: When and why did Earth and Venus become different? He said that this crustal growth rate plays into that a lot. It tells us how, what, and why planets evolved on different trajectories.
The study was co-authored by Joshua Davies from the University of Quebec at Montreal; Jean-François Moyen from the University of Lyon, France; and D. Graham Pearson from the University of Alberta, Canada.
The research was partly supported by the Natural Sciences and Engineering Research Council of Canada.
Parallel research
While Reimink’s research primarily delves into the evolution of Earth’s crust, focusing on the reworking of rock records over billions of years, a study published in Nature by Zhengbin Deng and his team challenges traditional beliefs about mantle convection and plate tectonics.
These findings are intriguingly interconnected and broaden our comprehension of Earth’s complex geological history.
Deng’s study proposes a stratification of mantle convection throughout most of Earth’s history, suggesting that plate tectonics were confined to the upper mantle during early Earth. This contrasts with the dominant belief that mantle convection has operated as a single layer since Earth’s formation 4.5 billion years ago.
The implications are profound, as it raises the possibility that the lower mantle may contain undisturbed primordial material, shedding light on Earth’s original composition and the source of essential volatiles necessary for the development of life.
In essence, Reimink’s work provides insights into Earth’s surface evolution and the long-term processes shaping it, while Deng’s study challenges established ideas about the dynamics of Earth’s interior.
Both studies together contribute to a more holistic understanding of our planet’s geological history, offering valuable context for ongoing research in the field.
This collaborative effort among scientists from different domains enriches our grasp of Earth’s complex geological past and its implications for the study of other celestial bodies.
The study was published in Geochemical Perspectives Letters
Study abstract:
Continental crust is a defining feature of Earth; yet, the mechanisms that control its growth remain hotly debated.
Many approaches to estimating crustal growth focus solely on a single mineral—zircon, while constraints from the lithospheric mantle root remain largely neglected.
Here, we critically examine the ability of zircon to accurately record the relative roles of juvenile crustal addition versus recycling, and present an alternative approach based on the geochemistry of crustal rock samples.
The resulting model of continental crustal growth parallels, but pre-dates, the pattern of cratonic mantle lithosphere formation ages, indicating a distinct relationship between the continental crust and its mantle root.
Our results indicate that continental crust and deep cratonic lithospheric roots grew progressively over ∼2.5 Gyr of Earth history, with clear temporal links to the birth of extensive lithospheric keels and establishment of continental drainage basins.
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Jerry Krause
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Hi. ,
“According to the existing theory, the Earth was a stagnant lid planet with no tectonic activity until a sudden shift to tectonic plates 3 billion years ago.”
I tend to agree with the idea that there was no tectonic activity before the Biblical flood (Genesis 7). For I reason that for a world wide flood required an almost ‘flat’ spherical surface. And after the flood water’s receded the dry land was much different and the atmosphere was much different as there were clouds and a rainbow. Much like we see today as we observe the slow continuing action originally termed continental drift. But there is nothing slow about volcanic eruptions which are referred to in The Holy Bible and which we struggle to fully understand even when we experience them.
However, I agree with the billions of years thing and the billions of stars thing because we see, with our space telescopes, the dust clouds which formed the physical earth and other planets of our solar system. And even though we have measured the speed of light and know it is very great, I accept from the light from the dust clouds have taken billions of years to reach these space telescopes.
However, we have observed physical natural laws that the dust particle cannot have a velocity near that of light. Therefore, we should not assume when our solar system began to be formed from gases and dust matter that was closer in space but isn’t there now because it is here now.
I make this comment because there is no reason to reject the SCIENCE we can read about in The Holy Bible.
Have a good day
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