Exploring Hidden ‘Supercontinents’: Astonishing Discoveries Revealing Earth’s Subsurface Secrets

Earth, like all of us, has plenty going on beneath its surface. One of the most interesting places is the mantle, the thick layer of rock located between the crust and the molten core. This area stretches about 1,800 miles (2,900 km) deep and is usually thought to be a homogenous mix of rock. However, new research reveals surprises—there are large, unmixed regions within the mantle, much like chunks of chocolate in a cookie.

Among these fascinating features are two massive “supercontinents.” One lies beneath Africa, while the other rests deep under the Pacific Ocean. Recent analysis of seismic data, gathered from earthquakes, has unveiled new insights about these ancient, submerged landmasses. Researchers suggest these supercontinents may be far older than we previously thought and could play a significant role in the behavior of the mantle.

This discovery connects to broader findings that shake up our understanding of how the mantle works. Instead of being smoothly blended, it seems there are hidden structures that may influence activities like plate movement. These findings were discussed in a recent article in Nature.

According to Claire Richardson, a doctoral candidate from Arizona State University, “these findings will contribute to a better understanding of mantle convection and plate tectonics, including earthquakes and volcanism.” She emphasized the difficulties of studying rocks nearly 3,000 km beneath us, but acknowledged that each new discovery brings us closer to understanding what’s happening down there.

The idea of buried supercontinents is not entirely new; they first emerged in seismic data about 50 years ago. Strong earthquakes produce seismic waves, which can reveal information about what lies below the surface. When these waves hit unusual structures in the mantle, they slow down, providing clues to scientists about Earth’s internal makeup.

These supercontinents are believed to comprise around 20% of the boundary between the mantle and core. They cover vast areas and can be nearly 600 miles (965 km) high. However, there has been little understanding of their composition or the role they play in mantle dynamics, according to Dr. Sujania Talavera-Soza, the study’s lead author.

There has been ongoing debate about their origins and whether they are stable structures or more temporary. Some earlier studies indicated that seismic waves slow down by about 2% when they encounter these regions, which geologists named large low shear velocity provinces (LLSVPs). This slow down suggests that these areas are hotter than the surrounding rock.

In the recent study, researchers adopted a fresh approach to explore these LLSVPs. They analyzed how seismic waves lose energy as they travel, examining the intensity of the signals to learn more about the zones’ composition. This method is akin to noticing how a musical note dissipates in sound, which can give hints about the material it travels through.

The study found that while seismic waves did slow down around the supercontinents, they didn’t lose much energy at all. In contrast, seismic waves lost more energy when traveling through cooler, silicate-rich areas surrounding these massive structures. Researchers attribute these differences to the ages of the formations: older regions usually contain larger mineral grains that cause less damping.

Dr. Talavera-Soza noted that the minimal damping observed in the LLSVPs indicates they are likely very old and could be over half a billion years old. This suggests they might act as anchors at the base of the mantle, enduring the constant movement within that layer. Such findings go against the belief that the mantle is entirely mixed.

These discoveries align with earlier studies suggesting that tectonic graveyards, remnants of old plates, lie around the supercontinents and those may also be more widespread than we thought. Scientists now believe these formations extend throughout Earth’s interior, reshaping our understanding of tectonic activity.

The new model developed in this study could enlighten seismologists about the Earth’s inner workings. It maps areas that weaken seismic energy, impacting measurements crucial for understanding our planet’s physical and chemical properties.

Furthermore, research into these ancient supercontinents could shed light on the origin of certain chemical elements found in volcanic activity. Should these findings spark further investigation into their composition, scientists could uncover ancient reservoirs of elemental materials, perhaps providing insight into Earth’s primordial past.

Overall, this groundbreaking research opens up a wealth of new questions and explorations, as scientists strive to decode the mysteries of our planet’s underground.