Deep within the bowels of the Earth, approximately 3,000 kilometers (1,864 miles) under our feet, exists an enigmatic layer known as the D” layer. Its oddly inconsistent thickness has sparked keen interest among researchers.
A new hypothesis suggests that the D” layer might be composed of remnants from an ancient magma ocean that is believed to have engulfed the Earth billions of years ago. This theory is supported by recent simulations by an international team of researchers.
According to their simulations, chemical reactions under extreme pressures and temperatures may have resulted in the variegated texture of the D” layer as observed today. Significantly, these simulations incorporated a factor often overlooked in previous models—the role of water in Earth’s primordial magma oceans and its effects during their cooling and solidification stages.
The study proposes that water could have interacted with minerals forming iron-magnesium peroxide, or (Fe,Mg)O2, which has a propensity to bond with iron. This discovery could answer why iron-rich strata are situated where the D” layer is found, right above the border separating Earth’s molten outer core and its mantle.
“Our research suggests this hydrous magma ocean favored the formation of an iron-rich phase called iron-magnesium peroxide,” explains Qingyang Hu, a data scientist at the Center for High Pressure Science and Technology Advanced Research (HPSTAR) in Beijing. “According to our calculations, its attraction to iron could have caused iron-dominant peroxide to accumulate in layers that could be several to tens of kilometers thick.”
This concentration of iron and the ensuing chemical reactions may have been the driving forces behind the creation of the D” layer, as per the team’s published paper.
Intriguingly, this could also shed light on the nature of ultra-low velocity zones (ULVZs), which are dense, slowly-seismic-wave-transmitting regions deep within the Earth.
The insulating properties of these iron-rich layers could have further implications, potentially maintaining distinct areas within the lower mantle.
“Iron-rich peroxide, created from ancient water within the magma ocean, appears to have played a critical part in sculpting the heterogeneous structures of the D” layer,” states Hu.
It is surmised that this magma ocean was formed due to a colossal impact with another celestial body approximately 4.5 billion years ago. This cataclysm not only led to the ejection of debris that would become the Moon, but also left behinf this combination of volatile elements crucial for life’s inception on Earth.
Revelations about the composition of our planet’s underbelly and its origins continue to be hotly debated among scientists. As our investigational methodologies evolve, so does our understanding of Earth’s primordial state.
“This model fits well with latest numerical modeling, proposing that the lowermost mantle’s heterogeneity might indeed be a long-standing feature,” remarks geophysicist Jie Deng from Princeton University.
The findings are detailed in National Science Review.
FAQs about Earth’s D” Layer
What is the D” layer?
The D” layer is a region of the Earth’s mantle that lies just above the core-mantle boundary. It features a variable thickness and exhibits complex chemical and physical properties.
Why is the D” layer important?
This layer helps us understand Earth’s internal structure and its thermal and chemical history. It plays a vital role in geodynamic processes and can impact the circulation of the mantle and core.
How was the D” layer formed?
The latest research suggests the D” layer may have been formed from reactions within an ancient magma ocean, facilitated by the presence of water, that led to the accumulation of iron-magnesium peroxide.
What are ultra-low velocity zones?
Ultra-low velocity zones (ULVZs) are areas within the D” layer where seismic waves travel unusually slowly, indicating the presence of particularly dense and possibly partially molten material.
How does the D” layer affect our understanding of Earth’s history?
Studying the D” layer provides insight into the conditions and processes that occurred during the early history of Earth, including the impact that may have formed the Moon.