What Are These Massive Blobs?

Indeed, experts have identified these large structures beneath the Earth’s surface. While "blob" may not be the most precise scientific term, it accurately depicts their form. Officially referred to as Large Low Shear Velocity Provinces (LLSVPs), I prefer to call them "the Blobs" for fun.

The challenge in naming these formations stems from the fact that scientists remain uncertain about their composition and nature. One of these blobs is located beneath Africa and part of the Atlantic Ocean, while another is situated under the Pacific Ocean.

Researchers believe these Blobs lie at the base of the Earth's rocky mantle, above the molten outer core, at depths exceeding 1,200 miles (2,000 kilometers). They are said to rise 100 times higher than Mount Everest and extend longer than entire continents. If they were to breach the surface, their height would necessitate that the International Space Station navigate around them.

The Depths of Pressure

At the deepest known point of the ocean, the Mariana Trench, which plunges nearly 7 miles down, the pressure is about 1,000 times greater than at sea level — equivalent to having 50 jumbo jets resting on each square meter of your body. If that seems extreme, consider the conditions over 1,000 miles beneath your feet near the molten core.

The Blobs are situated so deep that the Earth's elements there are compressed and transformed beyond recognition. A 3-D representation of these blobs, crafted by seismologist Sanne Cottaar from the University of Cambridge, illustrates their complexity.

Understanding the Blobs is significantly more intricate than studying outer space, primarily due to the extreme conditions near the Earth's core. As noted earlier, even fundamental elements become unrecognizable, indicating that not only would humans be unable to survive such conditions, but any equipment sent there would also succumb to the heat long before reaching its destination.

Discovery Timeline

Scientists have been aware of these blobs for several decades, dating back to the 1970s when seismic tomography was developed. This technology measures the waves produced by earthquakes as they travel through the Earth, allowing scientists to deduce their origins.

By analyzing the travel times of various seismic waves from numerous earthquakes, researchers constructed images depicting the planet's internal structure beneath the United States.

Ed Garnero, an Earth and Space Exploration professor at Arizona State University, remarked in an Eos article about the Blobs:

> "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."

If seismic waves are slower in certain regions, it suggests the presence of denser materials. While there is consensus on the existence of these blobs, their exact nature remains a matter of debate.

Theories and Technological Advances

Seismic data, however, cannot determine the density of the blobs or their material composition, leading to various theories. Some scientists speculate that the Blobs are akin to lava lamp-like plumes that supply volcanoes, particularly hotspot volcanoes like those in Hawaii, or even supervolcanoes capable of causing mass extinction events.

Others propose that the Blobs consist of dense formations of unique rock with unknown chemical properties. Furthermore, many experts believe that the Blobs might influence or even be responsible for Earth's vital plate tectonics.

Fortunately, modern technological advancements are propelling this research forward. In 2013, Linguo Yuan and her team at Academia Sinica in Taiwan published a groundbreaking paper in the Journal of Geophysical Research: Solid Earth, employing a novel approach to study the Blobs.

Instead of relying solely on seismic tomography, Yuan analyzed the Earth’s tidal movements caused by the gravitational pull of the Sun and Moon. These tides not only affect the oceans but also induce slight shifts in solid land, with some areas rising by over a foot (30 centimeters).

For 16 years, Yuan’s team meticulously tracked these land tides using highly sensitive GPS technology worldwide. They discovered that the tides were slightly misaligned above the Blobs.

Teaming up with Harvard postdoctoral researcher Harriet Lau, Yuan utilized the data to create models representing these anomalies. Lau concluded that the models aligning best with the data indicated that the Blobs were denser than the surrounding mantle. Their findings were published in Nature in 2017.

Conversely, another study published in the same year examined Stoneley modes, a type of standing wave that remains confined within an object. This study suggested that the Blobs may actually be less dense than the surrounding mantle, which could account for several observed phenomena.

Remarkably, these studies do not contradict one another, suggesting that the density of the Blobs may vary, being denser in some areas and less so in others. Recent research has provided further insights into their characteristics.

Latest Research Insights

In March 2022, scientists Qian Yuan and Mingming Li from the School of Earth and Space Exploration at Arizona State University published a study in Nature Geoscience.

They discovered that the blob beneath Africa is approximately 621 miles (1,000 kilometers) taller than its counterpart beneath the Pacific Ocean. They hypothesize that the density of these blobs influences their size and stability.

Presently, it is believed that the African Blob's lesser density contributes to its greater height and instability. This instability may account for the intense volcanic activity observed in certain African regions and could affect the movement of the tectonic plates above.

Unfortunately, despite the African Blob's instability, scientists remain uncertain about its origins or the potential consequences of this instability. There are various theories regarding the Blobs' formation.

One hypothesis suggests they are remnants from the cataclysmic collision that formed our Moon, while another postulates that they originated from superheated tectonic plates being pushed down. These theories are not mutually exclusive and may both play a role in the Blobs' existence. It's plausible that they were formed at different times, with the impact creating one and tectonic processes explaining the instability of the other.

A Shift in Perspective

Should the African Blob become too unstable, the consequences could be catastrophic. Given our limited understanding of these structures, the outcomes remain unpredictable. We can only hope they maintain their current state for the foreseeable future.

Regardless, it is exhilarating to realize that the center of our planet holds as many mysteries as the rest of the universe. It’s amusing how we humans often overestimate our understanding of everything, yet our predictions frequently fall short — nature's complexity far surpasses our comprehension.

It’s likely we will explore half the solar system before developing materials resilient enough to withstand a journey to study the Blobs directly. Until then, we can only speculate on what technologies may emerge to monitor and investigate these structures from above.

What we do know is that the Blobs rank among the largest formations within Earth, the only known planet exhibiting plate tectonics. Some studies even suggest that these tectonics may play a crucial role in supporting life by providing essential nutrients like nitrogen and phosphorus.

Could the existence of the Blobs be fundamental to the functioning of plate tectonics? Might they have contributed to the breakup of Pangea? The answers remain elusive, but the mere knowledge of their existence is awe-inspiring.

This article was originally published in the author’s newsletter, Curious Life, and was later edited and republished on Medium with her consent.

Katrina Paulson contemplates humanity, unanswered questions, and new discoveries, writing about them on Medium and in her newsletters: the free Curious Adventure Newsletter and the more in-depth Curious Life.

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