The Mysterious “Blobs” Near Earth’s Core Beneath Africa and the Pacific

 The Mysterious “Blobs” Near Earth’s Core Beneath Africa and the Pacific

Introduction to the Deep Mantle Blobs

Far beneath Earth’s surface—thousands of kilometers below continents and oceans—scientists have discovered two enormous structures hidden near the boundary between the planet’s mantle and its core. These mysterious formations are often referred to as “mantle blobs” or Large Low-Shear-Velocity Provinces (LLSVPs). One lies beneath Africa, and the other beneath the Pacific Ocean. Each is so massive that it dwarfs entire continents, yet they remain invisible to the human eye because they exist about 2,900 kilometers (1,800 miles) beneath Earth’s surface.

These giant structures were discovered using seismic tomography, a method that analyzes how earthquake waves travel through the Earth. When seismic waves pass through different materials inside the planet, they change speed. Scientists noticed that certain waves slowed dramatically when passing through two particular regions near the core–mantle boundary. These slow-wave regions appeared as enormous “blobs” on seismic maps, revealing something unusual deep inside the planet.

The African blob—sometimes called the African LLSVP—is thought to be thicker and possibly taller than the Pacific one. The Pacific blob, however, is far wider, stretching beneath a huge portion of the ocean basin. Together, these structures represent some of the largest geological features inside Earth.

Understanding these blobs is important because they may influence volcanic hotspots, plate tectonics, and the evolution of Earth’s interior. Some scientists believe they may even control where supervolcanoes and mantle plumes form. Others think they could be remnants of ancient planetary events dating back billions of years.

Although scientists have learned much about these deep mantle anomalies, many questions remain. Their composition, origin, and long-term role in Earth’s geology are still active areas of research, making them one of the most fascinating mysteries hidden inside our planet.

What Are the Deep Mantle “Blobs”?

Large Low-Shear-Velocity Provinces (LLSVPs)

The scientific term for these blobs is Large Low-Shear-Velocity Provinces, often abbreviated as LLSVPs. The name describes how they were detected. When earthquakes occur, they send out seismic waves that travel through the Earth. One type of wave, called shear waves, moves more slowly when passing through hotter or compositionally different materials.

In the regions beneath Africa and the Pacific, these waves slow down significantly. This slowdown indicates that the material there differs from the surrounding mantle. The anomalies appear as huge irregular masses sitting just above Earth’s outer core, forming structures thousands of kilometers across and hundreds of kilometers high.

Researchers estimate that each LLSVP could be over 1,000 kilometers tall and thousands of kilometers wide. If they were visible on the surface, they would be comparable in size to entire continents.

Scientists suspect that these regions are denser and hotter than the surrounding mantle. This combination may cause them to behave like massive piles of material slowly moving over geological time.

These structures are not static; instead, they may slowly evolve as heat and mantle currents circulate around the planet’s interior.

 

Location of the Two Giant Mantle Blobs

The African Blob

The African LLSVP lies deep beneath the African continent and parts of the Atlantic Ocean. Seismic studies suggest that this blob may extend upward farther than the Pacific one, forming a towering structure above the core–mantle boundary.

Some researchers believe this region may influence volcanic activity in Africa and surrounding areas. It has been linked to the formation of several major volcanic features, including:

• The East African Rift volcanic system
• The Canary Islands hotspot
• The Cape Verde volcanic chain

The African blob may also play a role in the gradual splitting of the African continent, where tectonic plates are slowly pulling apart.

 

The Pacific Blob

The Pacific LLSVP lies beneath a vast portion of the Pacific Ocean basin. It is broader than the African blob but may be slightly shorter in vertical height.

This structure appears to influence some of the most famous volcanic hotspots on Earth. Examples include:

• Hawaii
• Tahiti
• Samoa
• Easter Island

These volcanic chains form when mantle plumes—columns of hot material rising from deep within the Earth—reach the surface and create volcanoes.

Many scientists believe that these plumes may originate from the edges of the Pacific LLSVP.

 

How Scientists Discovered the Blobs

Seismic Tomography

Because humans cannot drill thousands of kilometers into the Earth, scientists rely on indirect methods to study the planet’s interior. One of the most powerful techniques is seismic tomography, which functions similarly to a medical CT scan.

When earthquakes occur, seismic waves travel through the Earth in all directions. These waves change speed depending on the temperature, density, and composition of the materials they pass through. By analyzing recordings from seismometers around the world, scientists can reconstruct a three-dimensional image of the planet’s interior.

During these studies, researchers noticed two enormous zones where shear waves slowed dramatically, indicating unusual material near the core–mantle boundary.

Over decades of research, improved seismic imaging confirmed that these anomalies were massive and persistent structures, now recognized as LLSVPs.

 

Possible Origins of the Mantle Blobs

Ancient Planetary Material

One theory suggests that the blobs are remnants of ancient material from early Earth. When the planet formed about 4.5 billion years ago, heavier elements sank toward the core while lighter materials rose toward the surface.

Some dense material may have accumulated at the base of the mantle and remained there for billions of years, forming the structures we observe today.

 

Remains of a Giant Impact

Another intriguing hypothesis connects the blobs to the giant impact that formed the Moon. According to this theory, a Mars-sized body called Theia collided with Earth about 4.5 billion years ago.

Some researchers suggest that fragments of Theia’s mantle sank deep into Earth and eventually settled near the core–mantle boundary. Over billions of years, these remnants may have formed the African and Pacific LLSVPs.

While this idea remains controversial, some computer simulations support the possibility.

 

Thermal Piles in the Mantle

A more widely accepted explanation is that the blobs are thermal piles—regions where dense, hot material accumulates due to mantle convection.

Earth’s mantle behaves somewhat like a slow-moving fluid over geological timescales. Hot material rises while cooler material sinks. This process may cause dense materials to gather into large piles near the core.

These piles could then act as sources for mantle plumes that create volcanic hotspots.

 

Why the Blobs Matter for Earth’s Geology

Connection to Volcanoes and Hotspots

One of the most important implications of the LLSVPs is their possible role in generating mantle plumes. Many of the world’s volcanic hotspots appear to originate near the edges of these deep mantle structures.

Examples include:

• Hawaii
• Iceland
• Galápagos Islands
• Yellowstone

These hotspots are responsible for some of the most powerful volcanic events in Earth’s history.

 

Influence on Plate Tectonics

The blobs may also influence mantle convection patterns, which drive the movement of tectonic plates. Because they are hotter and denser than surrounding mantle material, they can alter the flow of heat and rock inside the planet.

Over millions of years, these processes can affect the formation of continents, ocean basins, and mountain ranges.

 

Recent Discoveries and Ongoing Research

Recent studies suggest that the two blobs may not be identical. Research published in Nature Geoscience indicates that the African LLSVP may be less dense but taller, while the Pacific one may be denser but flatter.

Scientists are also investigating whether smaller mantle structures exist around the edges of these giant blobs. Some evidence suggests that these boundaries may generate clusters of mantle plumes.

As seismic imaging technology improves, researchers continue to refine models of Earth’s deep interior. Future discoveries may reveal whether these blobs are ancient relics of planetary formation or dynamic structures still evolving today.

 

Conclusion

The giant “blobs” beneath Africa and the Pacific represent some of the most mysterious and massive structures hidden inside Earth. Located near the boundary between the mantle and the core, these Large Low-Shear-Velocity Provinces play a crucial role in shaping the planet’s internal dynamics.

They may influence volcanic hotspots, mantle plumes, and the movement of tectonic plates. Their origins could date back billions of years, possibly to the earliest stages of Earth’s formation or even to the giant impact that created the Moon.

Despite decades of research, the deep mantle remains one of the least understood regions of our planet. As technology advances, scientists hope to uncover more details about these enormous structures and their role in Earth’s geological evolution.

The discovery of these blobs reminds us that even deep within our own planet, enormous mysteries still remain.

 

FAQs

1. What are the blobs near Earth’s core?

They are massive structures called Large Low-Shear-Velocity Provinces (LLSVPs) located near the boundary between Earth’s mantle and core.

2. Where are these blobs located?

One lies beneath Africa, and the other beneath the Pacific Ocean.

3. How large are the mantle blobs?

They are thousands of kilometers wide and may reach 1,000 kilometers in height, making them among the largest structures inside Earth.

4. How were the blobs discovered?

Scientists detected them using seismic tomography, which analyzes how earthquake waves travel through the Earth.

5. Why are these structures important?

They may influence volcanic hotspots, mantle plumes, and plate tectonics, shaping geological processes across the planet.