Recent discoveries reveal that undersea volcanoes off Madagascar’s coast are releasing chemical signatures from Earth’s primordial magma ocean. This magma ocean formed during the planet’s first 100 million years, offering insights into early Earth’s history.

Geologists posit that the Earth’s mantle—a vast layer of heated rock beneath the crust—has been slowly churning for over four billion years, gradually erasing chemical traces from Earth’s early formation.

“This discovery will significantly change our understanding in earth science,” states Catherine Chauvel from the French National Center for Scientific Research (CNRS) in Paris. “We now have proof that material dating back 4.5 billion years still exists in sufficient quantities to be studied in volcanic systems.”

During the Hadean era, a Mars-sized object collided with Earth, generating intense heat and forming a global magma ocean. As the molten rock solidified over millions of years, the oldest crust began to emerge.

While some scientists believed remnants of this primordial crystallization remained in the mantle, they lacked the analytical methods to confirm it, according to Chauvel.

An unusual swarm of earthquakes in May 2018 off Mayotte Island, located between Madagascar and Mozambique, led to the discovery of a new volcano, Fani Maore, approximately 50 kilometers eastward. Over the subsequent three years, eruptions released significant magma, causing the island to sink around 20 centimeters.

Chauvel and her research team collected volcanic rock samples from both Fani Maore and nearby Mayotte Island to analyze the chemical composition of the new volcano versus older volcanic systems. Collaborating with Claudine Israel, they are employing cutting-edge ultra-high precision techniques at the University of Cambridge to assess variations in neodymium isotopes, which preserve a chemical record of the crystallization process from Earth’s primordial magma ocean.

Initial findings indicate that Fani Maore’s lava has a higher proportion of neodymium-142 and neodymium-144 compared to that from Mayotte, suggesting pockets in the ancient mantle have remained undisturbed by billions of years of geological mixing. These pockets are relatively rich in bridgmanite, a mineral believed to have first crystallized from Earth’s primordial magma ocean.

“Finding something that has eluded others is always thrilling,” remarks Chauvel.

This discovery implies that Earth’s mantle may not have mixed as extensively as previously thought, thus aiding scientists in reconstructing how Earth’s primordial magma ocean solidified, according to Israel.

“We experimentally demonstrate how the mantle crystallizes from a magma ocean, creating chemical diversity from the very beginning,” she notes.

Tim Johnson at Curtin University in Perth, Australia, claims that this finding serves as compelling evidence that Earth’s mantle still houses ancient material. “This is a significant breakthrough,” he asserts.

“Despite the challenges in perfecting such technology, the results are impressive,” adds Bernard Bourdon from CNRS in Lyon.

This research provides unprecedented insights into an era of Earth’s history with limited direct evidence, akin to uncovering a core sample that made its way to the surface, Bourdon concludes.

According to Richard Carlson from Carnegie Science in Washington, D.C., the accuracy of this study is remarkable. “Those familiar with these measurements will recognize this achievement as substantial,” he remarks.