For centuries, humans have gazed at the stars, but a world of equal fascination exists right beneath our feet. The Earth’s subsurface holds countless mysteries and strange phenomena, from a second core within our planet’s heart to diamonds forged in its depths, and echoes of Earth’s cosmic voyages. The biggest mystery of all is how much remains unknown.
Who knows what other secrets scientists will unearth in the years to come? Let’s dig into ten of the most intriguing mysteries lurking beneath the Earth’s surface.
Subterranean Galapagos: An Ecosystem Brimming with Life
Did you know a massive ecosystem teems with microorganisms beneath our feet? Discovered at the American Geophysical Union’s 2018 meeting, this “Subterranean Galapagos” hosts billions of bacteria, archaea, and eukarya. Around 70% of Earth’s microbes thrive far below the surface, exceeding scientists’ expectations.
The diversity of life down under may even surpass that on the surface. Rick Colwell, a microbial ecologist at Oregon State University, notes that our understanding of subsurface life’s impact on surface life is limited. The metabolisms that allow life to endure in such harsh conditions are truly astonishing.
The Core of the Core of the Earth
Deep within Earth’s inner core lies another inner core—a colossal metal ball spanning 400 miles (643.7 kilometers). First theorized in 2002, its existence has since been confirmed. This adds a fifth layer to our planet’s structure: crust, mantle, outer core, inner core, and innermost inner core. Yet, much about this mysterious sphere remains unknown.
Scientists study seismic waves from major earthquakes to learn more. These waves traverse Earth’s diameter, bouncing back and forth, sometimes up to five times. By analyzing how these waves distort as they pass through the planet’s heart, researchers can catch glimpses of the innermost inner core.
Diamond Factory at the Earth’s Core
In 2022, researchers discovered a possible diamond factory nestled at Earth’s center. Using specialized technology at the U.S. Department of Energy’s Advanced Photon Source (APS), they replicated the extreme conditions of the planet’s core. High-energy X-rays and lasers generated immense heat and pressure, mimicking the environment miles below.
Around 90% of Earth’s carbon is estimated to reside in the core. When this carbon interacts with hydrous minerals from the oceanic crust, an interesting reaction occurs. The water and iron combine to form oxides and hydroxides, akin to surface rust. However, this process, under extreme conditions, can transform carbon into diamonds.
Never-Before-Seen Magnetic Waves
The Earth is constantly traversed by mysterious phenomena, but thanks to the European Space Agency (ESA) and its Swarm satellite project, we’re learning more. Scientists at ESA discovered a new type of magnetic wave by analyzing Swarm’s data. This wave sweeps across the outer core’s surface at an astonishing 932 miles per year (1500 km per year).
Nicolas Gillet, the study’s lead author, noted that geophysicists had theorized these waves for a long time, but they were thought to occur over much longer periods. Space-based measurements offered the global coverage needed to reveal the ongoing wave action.
Hallmarks of Earth’s Galactic Travels
In 2022, geologists tracked Earth’s journey through the Milky Way by examining tiny crystals from the earth’s crust. Though smaller than a hair’s width, these grains tell the story of an astronomical voyage. Researchers decoded the age and composition of these minerals to achieve this remarkable feat.
As the solar system moves through the Milky Way, icy debris is ejected from its outer reaches, some of which collides with Earth at incredible speeds (32.3 miles per second). Evidence of these high-energy impacts is preserved in the crystals, enabling geologists to plot the planet’s course across the cosmos.
Core Leaking Helium from Big Bang
A rare form of helium gas leaks from Earth’s core, potentially dating back to the universe’s beginning. A 2022 study showed how much helium-3 gas emanates from the planet’s heart. Helium-3 typically forms in solar nebulae, vast rotating disks of gas and dust. The evidence suggests Earth may have formed within one. Peter Olson, the lead author, calls it a wonder of nature and a clue to Earth’s history that significant isotopes remain inside our planet.
Giant River Under Antarctica
Beneath Antarctica lies a river that stretches 285 miles (460 kilometers), longer than London’s Thames. This immense waterway was discovered using an aircraft-mounted radar system. Aerial surveys revealed that the river flows under the Antarctic ice sheets and drains into the Weddell Sea.
Martin Siegert from the Grantham Institute at Imperial College London explains that scientists initially believed subglacial lakes were isolated. Now, they understand that entire interconnected systems exist with vast river networks, much like they would without the thousands of meters of ice above.
Hidden Zone Uncovered Beneath Tectonic Plates
A hidden zone of partly molten rock lies beneath the tectonic plates, according to scientists from the University of Texas. This elusive zone was unearthed in a 2023 study of the asthenosphere. The newfound layer resides in the upper mantle, around 100 miles (161 kilometers) below the surface, providing insights into the mantle’s inner workings.
The asthenosphere serves as a soft boundary between the upper mantle and the tectonic plates. While its exact operation is less understood, research suggests that heat and rock convection in the mantle significantly affect plate motion, rather than just melting.
Unidentified Structures Near the Core
In 2020, researchers found strange signs while examining seismic waves, indicating hot, dense rock regions between the core and the mantle. Scientists had previously seen hints of these structures, but the new research offered greater insight into their nature. Evidence of a previously unidentified structure beneath the Marquesas Islands in the South Pacific emerged from signals under the Pacific Ocean basin.
According to lead author Doyeon Kim, analyzing thousands of core-mantle boundary echoes simultaneously provided a completely new perspective compared to focusing on just a few at a time.
Goliath Ocean of Water
A vast reservoir beneath the surface houses enough water to fill all Earth’s oceans three times over! The discovery began in 2014 using thousands of seismometers that measured signals from around 500 earthquakes. Evidence of ringwoodite, a rock formed under immense pressure 400 miles (700 kilometers) below, emerged from the data.
Ringwoodite is incredibly absorbent. If even just 1% of the rock is below water, it indicates a record-breaking subterranean ocean. Geophysicist Steve Jacobsen explains that ringwoodite attracts hydrogen and traps water due to its special crystal structure, allowing it to contain significant amounts of water under the deep mantle’s conditions.
The mysteries beneath Earth’s surface are as captivating as those above. From hidden ecosystems and diamond factories to magnetic waves and subterranean oceans, our planet continues to surprise us. As technology advances, who knows what other wonders we’ll discover deep down?
What’s the most surprising thing you learned? Leave your comment below!
