Researchers have recreated the tumultuous beginnings of Earth, simulating what the planet was like just after its formation 4.5 billion years ago. The results, derived from a new computer model, provide a fascinating insight into the fiery youth of our planet, uncovering how Earth’s molten early years shaped its current geological structure.
A Molten World Cooled in Layers
When Earth first formed, it was not the solid land we know today. Instead, it was a searing ball of liquid rock, resembling more a lava lamp than the stable continents we stand on now. This molten state persisted for millions of years, during which Earth’s surface began to cool unevenly.
This cooling process didn’t happen uniformly. The top part of the planet cooled and solidified, while the lower sections, near the core, remained molten. The result was a “basal magma ocean,” a vast ocean of iron-rich liquid sitting just above the planet’s metal core. This concept, first proposed decades ago, has since been supported by seismic data that show sprawling zones in Earth’s mantle that slow seismic waves.
The basal magma ocean played a critical role in shaping Earth’s mantle and its thermal history. Evidence of these molten pockets, lying up to 1,800 miles beneath Earth’s surface, can still be found today in areas like the Pacific and parts of Africa. These pockets, however, are hard to observe, as they are situated far beneath the Earth’s surface.
New model offers groundbreaking insights
To better understand this early planetary state, scientists turned to the Bambari model, a computer simulation designed to recreate Earth’s first hundred million years. Led by Assistant Professor Charles-Édouard Boukaré from York University, the model took into account the complex behavior of Earth’s interior, which was only partially molten at the time.
The Bambari model began with a mantle that was about 50% liquid, a state deemed realistic following the giant impact that formed the Moon. The simulation tracked the movement of molten and solid rock within the planet’s early mantle, revealing that temperature differences caused lighter crystal mush to rise while heavier, iron-rich droplets sank. This process led to the formation of distinct layers within Earth’s early mantle, with the lighter minerals rising to the surface, while denser materials sank.
Surprising new chemistry beneath the surface
The simulation not only modeled the physical dynamics of Earth’s early years but also revealed unexpected chemical patterns. For example, minerals like olivine, typically found only in the upper mantle, were found as deep as 1,200 miles beneath Earth’s surface. This surprising discovery challenges previous ideas about how Earth’s minerals were distributed and points to a more complex segregation process within the planet’s early mantle.
The research suggests that the crystals formed near the surface before sinking into the mantle, where they partially melted, creating iron-rich pools of liquid rock. These pools eventually formed a liquid ocean about 300 miles thick above the core. This liquid blanket likely played a critical role in insulating the planet’s core, helping it retain heat for hundreds of millions of years.
The Legacy of Early Earth in Today’s Mantle
The Bambari model also demonstrated how the structure of Earth’s mantle today can be traced back to these early processes. The model predicts the existence of massive “superplumes”—large, low-shear-velocity provinces (LLSVPs)—located beneath the Pacific and African continents. These structures, which rise more than 600 miles off the planet’s core, are thought to be the remnants of the basal magma ocean.
These superplumes are responsible for volcanic hotspots, such as those found in Hawaii and Iceland. By studying these phenomena, scientists have drawn a link between Earth’s deep past and the volcanic activity we see today.
The Bambari model’s insights extend beyond Earth, providing valuable tools for studying the evolution of other rocky planets. For instance, the model predicts that Mars, with its smaller size and faster heat loss, would have had a much shorter-lived magma ocean, eventually losing its magnetic field and atmosphere far earlier than Earth. On the other hand, larger exoplanets could retain a magma ocean for much longer, potentially creating conditions for life to develop and sustain.
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