Widespread Ultra-Low Velocity Zones in Earth’s Mantle could be far more common than previously thought. New research sheds light on these mysterious features and their potential impact on our understanding of the Earth’s interior.

Widespread Ultra-Low Velocity Zones in Earth’s Mantle

Widespread Ultra-Low Velocity Zones in Earth’s Mantle are shaking up our understanding of Earth’s inner layers. Recent research suggests that these mysterious areas, known for slowing down seismic waves, might be far more common than scientists had previously believed. Let’s dive into what these zones are, how we discovered their potential widespread nature, and why it matters.

What Are Ultra-Low Velocity Zones?

Widespread Ultra-Low Velocity Zones in Earth’s Mantle refer to regions near the core-mantle boundary where seismic waves travel at significantly reduced speeds. These zones can slow down earthquake waves by up to 50%, making them an intriguing subject for geologists and geophysicists. They were first identified in areas close to volcanic hotspots, like Hawaii, where hot rock rises to the surface and forms volcanic island chains.

The Discovery of Widespread ULVZs

Michael Thorne, a geologist and geophysicist at the University of Utah, led a study published on August 10 in the journal AGU Advances. Although Thorne’s initial interest was in another mantle mystery, his research unexpectedly pointed to the potential prevalence of widespread Ultra-Low Velocity Zones in Earth’s Mantle.

Thorne and his team focused on very large earthquakes, particularly those occurring at subduction zones where one tectonic plate slides beneath another. These earthquakes generate powerful waves, including PKP waves, which travel through the mantle, outer core, and then back through the mantle to the other side of the planet. Sometimes, these waves are preceded by precursor PKP waves, which scatter off unknown features in the mantle.

To identify these features, Thorne’s team used computer models of the Earth’s mantle and introduced areas that altered the velocity of seismic waves. They noticed distinct patterns in how the waves changed speed. When they compared these patterns with real earthquake data, they found that something was causing dramatic delays in the waves.

Evidence of ULVZs Around the World

The researchers analyzed data from 58 deep earthquakes with magnitudes over 5.8 that occurred near New Guinea between 2008 and 2022. These waves traveled through the core and were recorded in North America by the EarthScope project, which had set up portable seismic monitors across the U.S. from 2003 to 2018.

The findings pointed to something significantly slowing down the earthquake waves, likely due to widespread Ultra-Low Velocity Zones in Earth’s Mantle. One possible explanation is that the core-mantle boundary under the western Pacific, where these waves passed, might have valleys or ridges affecting the waves. However, previous research had identified a large ULVZ under the western Pacific, near the Philippines, which overlaps with the study area.

The research also uncovered signs of widespread Ultra-Low Velocity Zones in Earth’s Mantle under North America, and previous studies have found similar zones beneath North Africa, East Asia, Papua New Guinea, and the Pacific Northwest. These findings suggest that ULVZs might not be confined to specific hotspots but could be scattered throughout the mantle.

Theories About ULVZ Formation

Some scientists speculate that widespread Ultra-Low Velocity Zones in Earth’s Mantle might be remnants of giant impacts during Earth’s early history, when meteorites bombarded the planet. However, if ULVZs are indeed widespread, it implies they could be actively formed today. Thorne proposes that these zones might originate from volcanic basalt formed at mid-ocean ridges. As this basalt is pulled into the mantle by subduction, it could melt and create pockets where seismic waves slow down. These pockets might then be moved around the mantle by other slabs of subducting crust, similar to stirring a smoothie.

The Impact of Understanding ULVZs

Grasping the extent and nature of widespread Ultra-Low Velocity Zones in Earth’s Mantle could significantly enhance our knowledge of volcanic hotspots and mantle dynamics. Understanding these zones better could help scientists comprehend how the Earth’s interior works, how volcanic hotspots are formed, and how the mantle moves.

Despite these exciting revelations, many questions remain unanswered. What exactly are these zones made of? How do they interact with other features in the mantle? And what role do they play in Earth’s geological processes? As research continues, geologists hope to uncover more about these enigmatic features and their impact on our planet.

In summary, widespread Ultra-Low Velocity Zones in Earth’s Mantle represent a crucial area of study in geophysics. The potential discovery of their widespread presence challenges existing models and opens up new avenues for understanding the dynamic processes beneath our feet. As scientists continue to explore these mysteries, we may gain deeper insights into the fundamental workings of our planet.

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