New Rock Type Made From Human Trash Discovered

Industrial Waste Is Becoming Rock in Just Decades, Scientists Find

Scientists have identified a novel rock type that has formed not over millions of years but within just 35. Dubbed rapid anthropoclastic rock, it arises from industrial slag—a by-product of 19th-century steel production—instead of natural sediments.

This unexpected lithification defies traditional rock-cycle models, which typically require thousands to millions of years. The discovery highlights how human by-products are swiftly reshaping Earth’s surface, creating new rock platforms composed predominantly of anthropogenic material.

The Evidence: A Can Tab and a Coin

Along a two-kilometer stretch of the Derwent Howe foreshore, rust-colored platforms have formed where waves erode historical slag heaps and redeposit the debris. Within these newly lithified slag deposits, researchers discovered unmistakable markers of modern human activity.

A key breakthrough came when researchers found modern artifacts embedded within the newly lithified material. Among them were:

• An aluminum drink-can tab, introduced no earlier than 1989
• A 1934 King George V coin

“These artifacts set a clear upper limit for the rock’s formation,” explains Dr. John MacDonald, co-author of the study. “The tab proves that the rock formed in less than 35 years—an incredibly short time by geological standards.”

How Waste Becomes Rock

Though it resembles natural sandstone, this material is entirely human-made. The source is slag, a glassy byproduct of 19th-century steelmaking. Rich in calcium, iron, magnesium, and manganese, slag undergoes chemical reactions when exposed to seawater and oxygen—triggering the formation of natural mineral cements.

To understand how these cements form, researchers used electron microscopy, X-ray diffraction, and Raman spectroscopy. They identified three key minerals binding the slag fragments into a coherent, rock-like mass:

• Calcite (calcium carbonate)
• Goethite (iron oxide)
• Brucite (magnesium hydroxide)

“These are the same types of minerals that bind grains in natural sedimentary rocks,” explains Dr. David Brown of the University of Glasgow. “But here, they’re forming from industrial debris—and they’re doing it fast.”

Anthropoclastic rock composed of industrial slag and waste debris along Cumbria's coastline, showcasing human-induced geological formations.

A New, Accelerated Rock Cycle

The process mirrors the classic sedimentary rock cycle: weathering, transport, deposition, and cementation. However, in this "rapid anthropoclastic rock cycle," anthropogenic materials replace natural sediments, and the timescale is reduced from millennia to mere decades.

“Instead of eroded mountains supplying sediment, we have slag from steel production. Instead of burial under pressure, it’s wave action and exposure to air that drives cementation,” notes Dr. Amanda Owen, a geologist on the team.

Local Formation, Global Relevance

Derwent Howe is not unique; industrial slag has been deposited along coastlines worldwide for over a century. The Glasgow team believes similar rock-forming reactions are likely occurring in coastal slag deposits across Europe, North America, and Asia.

“Wherever slag meets seawater, this process could be happening,” says Dr. Brown. “What we’re seeing in Cumbria might be a preview of widespread geological change.”

Redefining What Counts as "Rock"

This discovery blurs the boundary between natural and anthropogenic geology. Rocks, once defined strictly by natural origin and deep time, now include materials formed through industrial processes—raising important questions about how we define and teach the rock cycle.

Industrial slag and waste debris lithify into a new rock formation in West Cumbria within just 35 years — 1,000× faster than natural rock formation.

Coastal Ecosystems and Hazards

As loose slag lithifies, dynamic coastal environments become increasingly rigid. This transformation could:

• Alter natural erosion patterns
• Disrupt marine ecosystems
• Increase flood risks in nearby communities

“Our waste is not just polluting,” warns Dr. Amanda Owen. “It’s becoming a permanent part of the Earth's crust, reshaping shorelines and complicating coastal management.”

A Marker of the Anthropocene

From plastics embedded in deep-sea sediments to radioactive isotopes from nuclear testing, human activity has left distinct signatures in the geologic record. Now, industrial slag transformed into stone emerges as another hallmark of the Anthropocene epoch.

“This isn’t just waste—it’s the raw material of a new type of geology,” Dr. Owen adds. “We’re seeing human influence etched in stone.”

What’s Next?

The Glasgow research team plans to survey other post-industrial coastlines for similar lithification processes. Their work could fundamentally change how we understand waste, shoreline evolution, and the long-term geological imprint of human civilization.

“We thought we had centuries to deal with industrial waste,” says Dr. Owen. “It turns out we may only have decades before it becomes immovable geology.”

The study is published in the journal Geology.