Rocks take thousands to millions of years to be made, right? Wrong. Researchers have discovered that industrial waste has forged itself into rock over the course of just a few decades. This astounding discovery, made at Derwent Howe on the UK’s Cumbrian coast, challenges theories about how rocks are formed.
The rocks, which are a glassy texture and blue-grey colour, are made from slag, leftover from the iron and steel-making foundries that operated near Derwent Howe in the 19th and 20th centuries. Samples show the rocks contain many of the chemicals found in ordinary sedimentary rocks, but in this case hardened into solid rock within 35 years. An aluminium drinks tab dating to 1989 or later and a 1934 George V coin, fused into the new rock, are proof of its rapid formation.
Reporting in the journal Geology, the scientists say the new rocks are evidence for a rapid anthropoclastic rock cycle - where human activity is altering the landscape. Such rocks are likely to be commonplace in industrial areas all over the world (Britain alone has 120km of coastal slag deposits) and are likely to be having an impact on marine ecosystems and coastal erosion. The researchers are now using drones and ground-penetrating radar to better understand the rock-making process and its effect on the environment.
• This article was amended on 29 August 2025. An earlier version cited the study as saying this was proving we are in the Anthropocene era; however, the study said this was evidence for human activity altering the landscape, and could be used in the debate about geological epochs.
