Mystery spots occupy 3 to 9 percent of the Earth.
Earth, with the delicious goo inside on display.
Image credit: Vadim Sadovski/Shutterstock.com
Beneath Africa and the Pacific, in the lowest part of the Earth’s mantle, which surrounds the Earth’s core, are two giant blobs that take up about three to nine percent of the Earth’s volume.
Of course, there are no direct ways to see the Earth’s core, at least without burning yourself up or cutting your way through mole people. The deepest hole we’ve ever dug, sweetly known as the “gateway to hell,” reached 12,263 meters (40,230 feet), still a long way to go through the earth’s crust and into the lower . However, we can look below the surface quite effectively using earthquakes in a technique known as .
When earthquakes occur, waves of energy are sent in all directions. By measuring tremors from various locations on the surface, scientists can create a map of Earth’s interior. Since rocks and liquids within the Earth have different densities, waves move through them at different speeds, allowing geologists to determine what type of material the waves are passing through.
) , were found . In these areas, usually called “spots,” waves travel more slowly than through the surrounding lower mantle. Under Africa, the area known as “Tuzo” is believed to be about 800 kilometers (497 miles) high, or about .
So what are they? Unfortunately, we’re still not completely sure, although we do have some solid ideas. Since the objects are denser than the mantle around them, it is assumed that they are made of a different material, although we cannot say exactly what it is, nor the exact density, based only on seismic tomography data.
leading hypothesis is that the LLSVPs are mounds of oceanic crust that have subducted and accumulated over billions of years. Another slightly funnier theory is that the pieces are bits of an ancient planet.
is a hypothetical Mars-sized planet that struck Earth about 4.5 billion years ago, spewing enough rock to form the Moon. It has been suggested that the blobs are, in fact, pieces of : a denser mantle of the protoplanet that mixed with Earth’s during the collision. In 2021, a team modeled simulations of the scenario and found that Theia’s mantle could survive if it were only 1.5 to 3.5 percent denser.
Although we don’t know for sure what the spots are, and we’ll never see them directly, techniques for investigating beneath our feet are continually improving. Hopefully, it’s only a matter of time before we can refer to them for what they are, rather than the mysterious giant blobs that lurk deep beneath our feet.