Geological processes that create rocks typically occur over thousands or even millions of years, but researchers have identified rocks in England that formed in less than four decades due to human activity. Using a coin and a soda can tab, researchers from the University of Glasgow’s School of Geographical and Earth Sciences found that slag, a steel industry waste product, formed a new type of rock in West Cumbria in 35 years or less.
A study published on April 10 in the journal Geology details how these researchers documented and dated a “rapid anthropoclastic rock cycle” on land, an accelerated rock cycle incorporating human-made materials. This phenomenon may be affecting ecosystems and biodiversity at similar industrial waste sites worldwide.
According to Amanda Owen, co-author of the study, once waste materials are deposited, they can be moved around easily. However, the findings suggest that waste can turn into rock within decades, complicating management efforts. This is a concern because it impacts how long such materials can be stored with minimal environmental effect.
During the 19th and 20th centuries, Derwent Howe in West Cumbria was an industrial hub for iron and steel production. Factories there generated 953 million cubic feet of slag, creating cliffs along the coastline. These formations intrigued Owen and her colleagues. By studying 13 sites along the coast, they found that the slag contained calcium, magnesium, iron, and manganese. These elements, when exposed to seawater and air, form natural cements like brucite, calcite, and goethite, which typically bind natural sedimentary rocks over millennia.
Owen noted that finding these human-made materials becoming rock within decades challenges traditional understanding of rock formation and indicates significant future impacts due to waste materials used in modern development.
The presence of modern objects embedded in the lithified slag, such as a King George V coin from 1934 and an aluminum can tab from 1989, helped validate the dating of the material. Co-author David Brown suggested that similar processes are likely occurring at other coastal slag deposits around the world.
This rapid rock formation could significantly affect ecosystems and alter how coastlines respond to rising sea levels and extreme weather, said Owen. These developments are not currently reflected in land management and erosion models, which are crucial for adapting to climate change.
Looking ahead, the team aims to continue exploring this new Earth system cycle by studying other slag deposits. The study implies that humans are not only contributing to global warming but also accelerating ancient geological processes.
