Two giant blobs are lurking deep within the Earth, but why?

Earth’s violent forces, volcanoes and earthquakes, have long puzzled scientists. A recent study sheds light on their origins, proposing a cosmic collision billions of years ago as the culprit.

The culprit? Deep within Earth, researchers discovered two enormous, unusual blobs dubbed Large Low-Velocity Provinces (LLVPs). These mysterious masses, formed from the debris of a planet-sized impact, may hold the key to plate tectonics, the engine driving Earth’s geology.

The Improbable Past

Imagine a colossal smashup – Earth colliding with a planet the size of Mars. This cataclysmic event, estimated to have occurred 4.5 billion years ago, likely created the moon and left behind the LLVPs. Most scientists believe the impact debris became homogenized within Earth’s mantle over time. However, a 2023 study proposed that the LLVPs are remnants of the colliding planet, Theia.

“The moon appears to have materials within it representative of both the pre-impact Earth and Theia, but it was thought that any remnants of Theia in the Earth would have been ‘erased’ and homogenized by billions of years of dynamics (e.g., mantle convection) within the Earth,” Steven Desch stated, an astrophysicist at Arizona State University who co-authored the Nature study. “This is the first study to make the case that distinct ‘pieces’ of Theia still reside within the Earth, at its core-mantle boundary.”

A Twist in the Mantle

Building upon this theory, a new computer model suggests these hot, dense blobs stirred Earth’s interior roughly 200 million years after the impact. This churning may have triggered the formation of hot plumes that disrupted the planet’s surface. These plumes breached the crust, allowing slabs of rock to sink back down in a process called subduction.

This model aligns with the discovery of ancient zircon crystals – evidence of subduction over 4 billion years ago. The study’s co-author, Qian Yuan, suggests that the giant impact not only birthed the moon but also set the stage for plate tectonics, a crucial process for life.

Open Questions and Shifting Theories

While some geologists question whether the collision triggered plate tectonics or simply recycled Earth’s crust, another study throws a wrench into the mix. It suggests that life arose around 3.9 billion years ago, a time when plate tectonics may not have been active.

“We found there wasn’t plate tectonics when life is first thought to originate and that there wasn’t plate tectonics for hundreds of millions of years after. Our data suggests that when we’re looking for exoplanets that harbor life, the planets do not necessarily need to have plate tectonics,” paleogeologist at the University of Rochester, John Tarduno stated.

The Enduring Mystery

The debate surrounding plate tectonics and its role in the emergence of life continues. While some believe it’s essential for the carbon cycle that sustains life, others posit that life arose without its influence. The quest to understand how, when, and why life first appeared on our dynamic planet, and the role these shifting plates played, remains an ongoing scientific adventure.