The coastline near Derwent Howe, in England’s Cumbria, hardly seems a place where geologists would find new things. They’ve been studying the area for two centuries and mapped the region in great detail. But, in recent years, something different started popping up. Among the well-known rocks, researchers are finding small, gleaming objects: an aluminum tab from a soda can, a bit of copper, a zipper.

It’s not just litter. It’s entombed in a new kind of rock.

This discovery led scientists down a rabbit hole that opened up a new chapter in geology. Turns out, humanity’s industrial waste isn’t just polluting the landscape. It’s becoming part of it, turning to stone within mere decades. “What’s remarkable here is that we’ve found these human-made materials being incorporated into natural systems and becoming lithified — essentially turning into rock — over the course of decades instead,” said Dr. Amanda Owen of the University of Glasgow. “It challenges our understanding of how a rock is formed, and suggests that the waste material we’ve produced in creating the modern world is going to have an irreversible impact on our future.”

Earth’s geology on steroids

For centuries, geologists learned that rock formation was almost always a slow and patient process. Natural rocks, like the sandstones of deserts or the limestones of coral reefs, emerged over thousands to millions of years. They formed through gradual burial, compression, and chemical bonding. Sure, some volcanic rocks can form quickly through the cooling of lava, but that’s a special case.

However, along the two-kilometer stretch of Derwent Howe, that no longer seems to be the case.

The site was important for the Industrial Revolution. From the 1850s to the 1980s, Britain’s iron and steel industry poured millions of cubic meters of furnace slag onto this coastline​. Then, the waves and tides chewed away at the cliffs, scattering slag fragments across the shore. Over time, seawater and air also played a role, interacting with the minerals around to form a sort of natural cement.

This type of geological process happens around many coastlines around the world. What’s different now is that this uses man-made materials instead of natural ones. Also, because of the particularities of man-made materials, the process doesn’t take eons. It takes decades.

In some places, the waste hardened into platforms and outcrops that blend in with natural stone at a glance. But within these rocks, the researchers found artifacts: a King George V coin from 1934, pieces of clothing, plastic, and the notable aluminum can tab, a design not manufactured before 1989​.

“This gives us a maximum timeframe of 35 years for this rock formation, well within the course of a single human lifetime,” said Dr. John MacDonald, another co-author of the study. “This is an example in microcosm of how all the activity we’re undertaking at the Earth’s surface will eventually end up in the geological record as rock, but this process is happening with remarkable, unprecedented speed.”

What’s happening at Derwent Howe isn’t an isolated case. On beaches in Hawaii, researchers have documented “plastiglomerates,” rocks fused with fishing nets, bottles, and other fragments of plastic melted by campfires or volcanic heat. In Madeira, Portugal, scientists found “plasticrusts”—thin veneers of polymer coating seaside rocks like a second skin. Together, these strange formations are being dubbed “technofossils”—a geological record of modern life as indelible as trilobite or ammonite fossils. But unlike those ancient organisms, our contribution is made of zippers, coins, and can tabs.

The Anthropocene world

The transformation happening at Derwent Howe is not a local oddity. This is probably happening at a much larger scale but hasn’t yet been dsicovered. “Steel slag waste is a global phenomenon,” said Dr. David Brown, the paper’s third co-author. “As we’ve documented, when alkaline mine wastes are exposed to water and air, there is potential for cementation of loose material.”

This rapid rock cycle challenges our very definitions of what a rock is. Classical geology defines rock as naturally formed solid material. But when waste bonds into a hard, cohesive mass through natural processes, is it no longer artificial? “It is debatable as to whether the cemented material at Derwent Howe can be considered a ‘rock’ depending on the particular definition adopted,” the study notes.

This research also makes a strong case in the Anthropocene debate.

The Anthropocene — a proposed epoch marking humanity’s geological impact — is full of strange new materials, from plastics embedded in sediments to fallout from nuclear tests. Some researchers claim that we’ve made a big enough impact to be catalogued as a new geologic age, but not everyone is convinced. This new type of rock adds even more weight to the idea that an Anthropocene exists.

There are also practical concerns regarding this finding: plastic pollution is becoming permanent. “We don’t have as much time as we thought to find somewhere to put [industrial waste] where it will have minimal impact on the environment,” Owen warned. “Instead, we may have a matter of just decades before it turns into rock, which is much more difficult to manage.”

The team at the University of Glasgow is now seeking funding to explore other coastal slag sites across Europe. They want to know how widespread — and how fast — this process really is.

The study was published in the journal Geology.

This article was originally published in April 29, 2025, and has been edited to include more information.