Chapter 1: Unveiling the Secrets of the Earth's Interior

While humans inhabit a significant portion of the Earth's land, much remains a mystery. The oceans are only 20% explored, leaving around 80% of their depths uncharted. This discrepancy once led me to ponder why we have a greater understanding of outer space than our own oceans. It turns out that outer space is often more accessible for study than the depths of our oceans and the interior of our planet. However, advancements in technology are enabling scientists to explore the Earth in novel ways, leading to surprising discoveries—specifically, enormous structures known as "blobs" located near the Earth's core.

What Are These Enormous Blobs?

You read that correctly. Researchers have identified colossal formations near the center of our planet. While "blob" may not be the most precise term, it aptly conveys their nature. Some specialists refer to them as Large Low Shear Velocity Provinces (LLSVPs), but for simplicity, I'll stick with "blobs." The challenge lies in the fact that scientists are still uncertain about their composition and origin. One of these blobs is situated beneath Africa and part of the Atlantic Ocean, while another is located beneath the Pacific Ocean.

These blobs are believed to reside at the bottom of the Earth's rocky mantle, positioned over the molten outer core, more than 1,200 miles (2,000 kilometers) beneath the surface. They tower 100 times higher than Mount Everest and stretch longer than entire continents. If they were to rise above the surface, they would be so immense that the International Space Station would need to navigate around them.

To put this into perspective, consider the Mariana Trench, the deepest known oceanic point, which plunges nearly 7 miles down. Here, pressure is about 1,000 times greater than at sea level, equivalent to the weight of 50 jumbo jets per square meter. Now imagine the extreme conditions over 1,000 miles below the Earth's surface, near the molten core. The blobs are so far down that even the Earth’s basic elements are compressed and melted beyond recognition. For a visual representation, refer to this 3-D animation of the blobs, courtesy of seismologist Sanne Cottaar from the University of Cambridge.

Understanding these blobs is far more complex than studying space due to the harsh conditions near the Earth's core. Even raw materials lose their identity in those depths, meaning not only would humans be unable to survive the journey, but any equipment would likely melt long before reaching the destination.

How Were These Blobs Discovered?

The existence of these blobs has been known for decades, dating back to the 1970s when scientists first observed them through seismic tomography. This technology tracks seismic waves generated by earthquakes, allowing researchers to determine their origin.

By analyzing the travel times reported by thousands of seismic instruments, scientists were able to create images depicting the planet's internal structure beneath the United States. According to Ed Garnero, a professor of Earth and Space Exploration at Arizona State University, "It was very clear in those models from the get-go that at the bottom of Earth's mantle, nearly halfway to the center, there were these huge zones where the waves traveled more slowly." The slower wave speeds indicate denser materials obstructing their path.

Section 1.1: The Nature of the Blobs

Despite the consensus on their existence, scientists disagree on the specific nature of these blobs. Some propose that they are akin to lava lamp-like plumes that supply volcanoes, particularly hotspot volcanoes like those in Hawaii. Others suggest they are dense accumulations of unique rock with unknown chemical properties. Additionally, many experts theorize that the blobs may influence, or even be responsible for, Earth's tectonic plate movements, which are crucial for sustaining life.

Recent technological advancements are propelling research forward. In 2013, a team led by Linguo Yuan at Academia Sinica in Taiwan published findings in the Journal of Geophysical Research: Solid Earth, employing a novel approach to visualize the blobs. Instead of traditional seismic tomography, Yuan examined the Earth's tides, which are influenced by the gravitational forces of the Sun and Moon.

Over 16 years, Yuan and her team used highly sensitive GPS technology to track these land tides globally. They discovered that the Earth's tides were not as uniform as anticipated, appearing to deviate directly above the blobs. Collaborating with Harvard's Harriet Lau, they created models that suggested the blobs possess greater density than the surrounding mantle. Their findings were published in Nature in 2017.

A different study, also from 2017, examined the Stoneley modes—vibrational waves that remain within an object—finding that the blobs might actually be less dense than their surroundings. Remarkably, the studies do not negate each other; it’s plausible that the blobs have varying densities, being denser in some regions and less so in others.

Subsection 1.1.1: Recent Discoveries and Theories

Chapter 2: The Height and Stability of the Blobs

In March 2022, scientists Qian Yuan and Mingming Li from Arizona State University released a study in Nature Geoscience, revealing that the blob beneath Africa reaches about 621 miles (1,000 km) taller than its Pacific counterpart. They theorize that the density of these blobs influences their size and stability.

Currently, they believe the African blob's height is due to its lower density compared to the Pacific blob, rendering it more unstable. This instability may explain the heightened volcanic activity observed in some African regions and could affect tectonic plate movements.

While the African blob's instability raises concerns, experts remain uncertain about its origins, potential future activity, or any consequences that may arise. Some theories posit that the blobs are remnants from the collision that formed the Moon, while others suggest they originate from superheated, subducted tectonic plates. Both hypotheses may contribute to our understanding, indicating that the blobs' formation could be a complex interplay of historical geological events.

Perspective on the Blobs

If the African blob were to become critically unstable, the consequences would likely be catastrophic. Given our limited understanding, the potential outcomes are unpredictable. However, it is exhilarating to learn that the Earth's core is as enigmatic as the cosmos.

Humans often overestimate our grasp of knowledge, yet nature continually surprises us with its complexity. It’s likely we will explore much of the solar system before we develop technology capable of withstanding the journey to the blobs, perhaps after visiting Venus, which has a scorching average temperature of 867°F (464°C).

Ultimately, we know that the blobs rank among the largest structures within the Earth, which is the only known planet with plate tectonics. Some studies suggest that these tectonic activities may play a crucial role in sustaining life on the planet by delivering essential nutrients.

Could the blobs be integral to the existence of tectonics? Did their formation contribute to the breakup of Pangaea? These questions remain unanswered, but the mere knowledge of their existence is fascinating.

This article was originally published in the author’s newsletter, Curious Life, and has been edited and republished on Medium with permission.

Katrina Paulson is dedicated to exploring humanity's biggest questions, inspiring discoveries, and sharing insights through her writing. Subscribing to her newsletters—Curious Adventure and Curious Life—grants access to her articles and a wealth of archived content. Your support helps her continue her passion for inquiry and sharing knowledge.

Explore more about the mysterious "blobs" towering beneath our feet in the video titled "Giant 'Blobs' 100X Taller Than Mt. Everest Inside Earth's Mantle!"

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