Ten Mysteries from Beneath the Earth’s Surface

For years, mankind has looked up at the stars, but in many ways, there is a world just as fascinating below us as there is above us. Beneath our feet, lying under the surface of the Earth, is a whole world of mysteries and strange phenomena. A second hidden core within the core, diamonds churned out by the dozen, the leftover signs of Earth’s cosmic travels—these are just some of the treasures lying within.

And perhaps most mysterious of all is that there is still so much more unknown down there. Who knows what else scientists might uncover in years to come?

Related: Top 10 Things You Should Know About Asteroid Collisions With Earth

10 Subterranean Galapagos: An Ecosystem Bimming with Life

Beneath the surface of the Earth, there lies an enormous ecosystem, and it is chock full of microorganisms. As revealed at the American Geophysical Union’s 2018 meeting, billions of tiny bacteria, archaea, and eukarya exist among a smorgasbord of subterranean life. Around 70% of all Earth’s microbes dwell down there, far more than the scientists involved in the study had anticipated finding.

There are even suggestions that the diversity of life in this “Subterranean Galapagos” may be greater than there is here on the surface. “Our studies of deep biosphere microbes have produced much new knowledge, but also a realization and far greater appreciation of how much we have yet to learn about subsurface life,” explained Rick Colwell, a microbial ecologist at Oregon State University. “For example, scientists do not yet know all the ways in which deep subsurface life affects surface life and vice versa. And, for now, we can only marvel at the nature of the metabolisms that allow life to survive under the extremely impoverished and forbidding conditions for life in deep Earth.”^[1]

9 The Core of the Core of the Earth

Earth’s inner core has its own inner core—a giant ball of metal 400 miles (643.7 kilometers) across. Experts first theorized about this mysterious body in 2002 and have since proved its existence on several occasions. Before that, it was thought that our planet was made of four layers: the crust, the mantle, and the outer and inner core. But now scientists can add the innermost inner core to that list, although very little is known about it.

To find out more, scientists are studying the ripples caused by large earthquakes. These seismic waves dart along Earth’s diameter, ping-ponging to and fro, sometimes as many as five times. By investigating how the waves are distorted as they pass through the heart of the planet, researchers can catch a glimpse of the innermost inner core.^[2]

8 Diamond Factory at the Earth’s Core

In 2022, researchers uncovered a potential diamond factory squirreled away at the center of the earth. The team—from the U.S. Department of Energy’s Advanced Photon Source (APS)—used specialized technology to mimic the extreme conditions of the planet’s core. High-energy X-rays and lasers create enormous heat and pressure similar to that found miles beneath our feet.

Scientists estimate that around 90% of the carbon on Earth lies at the core. Sometimes, that carbon interacts with hydrous minerals that have descended from miles above in the oceanic crust. Scientists from the APS decided to investigate what happens when carbon, water from the minerals, and molten iron from the core combine under extreme conditions. As it turns out, the water and iron react to create oxides and hydroxides, similar to how metal rusts here on the surface. But the one difference is that the liquid melting pot may transform all that carbon into diamonds.^[3]

7 Never-Before-Seen Magnetic Waves

All types of strange and elusive phenomena pass through the Earth every day, from shadowy particles to unknown waves. But thanks to the European Space Agency (ESA) and their satellite project Swarm, we now know a little more about our planet’s internal happenings.

By analyzing data collected by Swarm, scientists at the ESA found an entirely new type of magnetic wave. This unprecedented ripple sweeps the surface of the outer core at a speed of 932 miles per year (1500 km per year). It sounds slow, but it’s far more rapid than scientists anticipated.

“Geophysicists have long theorised over the existence of such waves,” explained Nicolas Gillet, lead author of the study, “But they were thought to take place over much longer time scales than our research has shown. Measurements of the magnetic field from instruments based on the surface of Earth suggested that there was some kind of wave action, but we needed the global coverage offered by measurements from space to reveal what is actually going on.”^[4]

6 Hallmarks of Earth’s Galactic Travels

In 2022, geologists tracked Earth’s path as it soared through the Milky Way. And how did they do this? By examining minute crystals from the earth’s crust. These grains are tinier than the width of a hair, yet they tell the tale of an astronomical voyage.

Researchers pulled off this remarkable feat by decoding the age and composition of these minerals. As the solar system shifts across the Milky Way, icy debris gets knocked out of its outer reaches and soars inward. Some of the material is thought to slam into Earth, striking at 32.3 miles per second (52 km/s). Evidence of these high-energy impacts remains preserved in tiny crystals in the crust, enabling geologists to plot the planet’s course across the cosmos.^[5]

5 Core Leaking Helium from Big Bang

A rare form of helium gas is escaping from the earth’s core, and scientists reckon it could date back to the formative stages of the universe. In a 2022 study, researchers at the American Geophysical Union demonstrated just how much helium-3 gas is emitted from the heart of the planet.

Helium-3 is most often created in enormous, rotating disks of gas and dust known as solar nebulae. Many astronomers believe that the solar system was born inside a solar nebula, and this newfound evidence suggests that Earth could have been too. “It’s a wonder of nature,” explained lead author Peter Olson, “and a clue for the history of the earth that there’s still a significant amount of this isotope in the interior of Earth.”^[6]

4 Giant River Under Antarctica

Deep beneath Antarctica, there lies a river that stretches for 285 miles (460 kilometers), longer than London’s Thames. Scientists uncovered the behemoth water feature using an aircraft-mounted radar system. Aerial surveys revealed the gigantic river to run beneath the Antarctic ice sheets and drain into the Weddell Sea.

“When we first discovered lakes beneath the Antarctic ice a couple of decades ago, we thought they were isolated from each other,” said Martin Siegert from the Grantham Institute at Imperial College London. “Now we are starting to understand there are whole systems down there, interconnected by vast river networks, just as they might be if there weren’t thousands of meters of ice on top of them.”^[7]

3 Hidden Zone Uncovered Beneath Tectonic Plates

A hidden region of partly molten rock lurks beneath the tectonic plates. So say scientists from the University of Texas, who unearthed the elusive zone in a 2023 study into the asthenosphere.

This newfound layer is part of the upper mantle, lying around 100 miles (161 kilometers) under the surface. Its discovery sheds new light on the inner workings of the mantle. Scientists know that the asthenosphere acts as a soft boundary of sorts between the upper mantle and the tectonic plates. But exactly how that boundary works is less understood. This new research indicates that heat and rock convection in the mantle has a major effect on plate motion and not melt, as previously thought.^[8]

2 Unidentified Structures Near the Core

In 2020, geophysicists from the University of Maryland announced that they had discovered something strange while scouring through the records of seismic waves. The data showed signs of hot regions of highly dense rock between the core and the mantle.

Scientists had already caught a glimpse of the structures before, but the new research gave greater insight into their nature and properties. By studying signals from under the Pacific Ocean basin, the Maryland team pieced together evidence of a previously unidentified structure beneath the Marquesas Islands in the South Pacific.

As lead author Doyeon Kim explained, “By looking at thousands of core-mantle boundary echoes at once, instead of focusing on a few at a time, as is usually done, we have gotten a totally new perspective.”^[9]

1 Goliath Ocean of Water

One giant reservoir under the surface contains enough water to fill every ocean on Earth three times over. The discovery of this Goliath waterway began in 2014 when U.S. scientists deployed thousands of seismometers to measure the signals from some 500 earthquakes. The data displayed evidence of ringwoodite—a rock formed under immense pressure 400 miles (700 kilometers) beneath our feet.

Ringwoodite is incredibly absorbent, and researchers have calculated that if just 1% of the rock is below water, that points to a record-breaking subterranean ocean. “The ringwoodite is like a sponge, soaking up water. There is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water,” geophysicist Steve Jacobsen told reporters. “This mineral can contain a lot of water under conditions of the deep mantle.”^[10]