There is much talk of man going to inhabit other planets, such as Mars. Yet, there is still so much of our own planet we have yet to explore and understand. For example, our oceans take up 70% of the Earth’s surface, yet we have only explored 26.1% of its depths! The Earth’s core is another aspect of our planet that we know very little about. In fact, there are two massive “blobs” located beneath the Pacific Ocean and Africa that account for 6% of our planet’s entire volume. However, we still don’t actually know what caused them or what they are.
What Are the Structures Beneath Africa?
There are several hypotheses as to what these “blobs” might be, such as gigantic piles of oceanic crust that have built up over billions of years. Another theory suggests that the structures are massive pieces of a planet that collided with the Earth approximately 4.5 billion years ago. Just how big are these structures though? Well, the one under Africa is estimated to be around 1,000km tall. According to IFLScience, that’s the equivalent of approximately 90 Mount Everest’s stacked on top of each other. These structures are known as Large Low-Shear-Velocity Provinces (LLSVPs) and are significant features in Earth’s mantle.
Difficulties Determining Dates
The biggest difficulty when it comes to trying to determine the origin of these massive structures is that we don’t have any direct ways of studying the core of our planet. The deepest hole ever dug by humans reached an incredible depth of 12,263m. However, this is nothing when compared to how deep we would have to dig to reach the core. Seismic tomography is our most efficient method for analyzing what is beneath the surface of our planet. This technology works by studying the movement of energy waves during earthquakes.
Seismic Tomography Uses
Waves flow at different rates through liquids and rocks because their densities differ. Geologists are able to identify the type of material through which the waves are traveling by monitoring the tremors at various points on the surface. This essentially allows us to effectively map the Earth’s interior. The two massive structures beneath Africa were discovered using this technique. According to a geodynamics researcher at GFZ German Research Centre of Geosciences and the University of Oslo in Norway, Bernhard Steinberger, “These features are very large, very prominent in tomography”.
Waves move slower in these places than in the area surrounding the lower mantle, which suggests that they are most likely comprised of a different material.
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The Theia Theory
We aren’t able to figure out what this material is using seismic tomography alone. There are some scientists, however, that have been exploring the “giant impact hypothesis”. This hypothesis puts forward the idea that an object the size of Mars collided with our planet around 4.5 billion years ago. This collision not only produced the planet we live on today, but it also displaced enough rock to produce the moon. A few scientists even believe that some of Theia’s remains sank to the planet’s core, most likely settling somewhere above it, generating at least one of the two LLSVPs. However, this is still a topic of debate among researchers.
More Data Is Needed
While researchers have been investigating these structures under Africa and the Pacific Ocean for decades now, they still are not really any closer to learning the truth of their origins and composition. “We really know much less about the Earth’s mantle than about outer space where we can look with telescopes, because everything we know is very, very indirect,” emphasized Steinberger. Nonetheless, research into the hypothetical planet has provided essential insights into how the impact may have triggered key plate tectonic and mantle movements within our planet. This could provide us with insight into the critical processes required for forming the world in which we live.
The Bottom Line
Though the deep-Earth blobs remain as perplexing as ever, they are already positioned to reveal some of Earth’s mysteries. It may even potentially reveal insights about a long-lost alien world. Maybe one day we’ll discover an even better technique to see inside the Earth and observe these strange and massive structures. What do you think they could be?
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