Scientists suggest a Mars-sized impactor that helped form the Moon also deposited dense, iron-rich material into Earth’s deep mantle. Dr. Garrett Apuzen-Ito of the University of Hawaiʻi says that material could now reside in vast low-velocity zones beneath the Pacific and Africa. These deep blobs can feed mantle plumes that produce hotspots like Hawaiʻi, linking an ancient collision to modern volcanism.
Cosmic Collision That Created the Moon May Have Seeded Hawaiʻi’s Volcanic Hotspot
Scientists suggest a Mars-sized impactor that helped form the Moon also deposited dense, iron-rich material into Earth’s deep mantle. Dr. Garrett Apuzen-Ito of the University of Hawaiʻi says that material could now reside in vast low-velocity zones beneath the Pacific and Africa. These deep blobs can feed mantle plumes that produce hotspots like Hawaiʻi, linking an ancient collision to modern volcanism.
09:19 AM, 11/18/2025Science
HONOLULU — Scientists continue to reconstruct the dramatic events that formed Earth and the Moon. One influential hypothesis proposes that a Mars-sized body struck the young Earth, launching debris that formed the Moon and forcing denser material to sink deep into Earth’s interior — possibly leaving a remnant beneath the Pacific, under Hawaiʻi.
Dr. Garrett Apuzen-Ito, professor of earth sciences at the University of Hawaiʻi, explains that this scenario dates back to the solar system’s earliest days. “Very early on, when the planets were forming and shortly after Earth itself took shape, a Mars-sized body is thought to have struck Earth. Parts of that impactor and the Earth were flung away and reassembled to make the Moon,” he said.
A hidden remnant in the deep mantle
Researchers suggest that while some material from the impact escaped into orbit to become the Moon, other fragments sank into the young Earth. The new study published in Nature proposes that some of this material was richer in iron than the average mantle and would have settled into the deep mantle — the iron–magnesium silicate layer that makes up roughly half of Earth’s mass and extends nearly 3,000 kilometers.
“A portion of that body sank into Earth,” Apuzen-Ito said, noting that the study suggests this material is denser and compositionally distinct from typical mantle rock.
Seismic imaging reveals two enormous regions in the lowermost mantle beneath the western and central Pacific and beneath Africa. These regions — often called large low shear velocity provinces (LLSVPs) — slow seismic waves and appear less rigid and comparatively hotter than surrounding mantle. Scientists describe them as continent‑sized “blobs” that may have persisted for billions of years.
From deep blobs to island chains
As Earth’s early magma ocean cooled and solidified, the sinking impactor material could have contributed to chemical layering near the core‑mantle boundary. That layering can affect how heat and rock circulate today and may help anchor the deep, hot zones that feed mantle plumes.
Mantle plumes are buoyant, hot upwellings that rise from deep within Earth. When a plume reaches the base of the Pacific plate beneath Hawaiʻi, it partially melts the overlying rock and supplies magma to volcanic systems. As the Pacific plate moves over a relatively stationary plume, a chain of islands like Hawaiʻi forms in the plume’s wake.
While this hypothesis does not change daily life, it offers a striking view of how cataclysmic early events may have shaped both the Moon and long‑lived structures deep beneath Earth — and how those deep structures can influence surface features like Hawaiʻi’s volcanoes.
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