Scientists have made a surprising discovery about the formation of rock. It seems that industrial waste known as slag that is generated by the steel industry can turn into new, solid rock within about 35 years, under certain conditions. This shocking finding has challenged what we thought we knew about geology, which is to say that it may not take millions of years for rock to form through natural processes; it may only take a few decades with the right stuff. The research, which documents a so-called "rapid anthropoclastic rock cycle," has been reported in the journal Geology.
This rock cycle seems to mimic the natural processes of rock formation, but rapidly accelerates them. The researchers suggested that this phenomenon may be occurring at other similar industrial areas worldwide. It could also be having a detrimental effect on ecosystems, and may influence coastal or land use or management.
In this work, the researchers analyzed 2 kilometers of slag waste at the former location of iron and steel foundries, which were in use in the 19th and 20th centuries at Derwent Howe in West Cumbria, England. About 27 million cubic meters of furnace slag accumulated here while these foundries operated, creating cliffs of industrial waste on a coast that is now being eroded by tides and waves.
As the erosion occurs, the stuff in the slag is exposed to air and seawater, and chemical reactions between their components start.
The researchers used a variety of tools to assess samples from irregular parts of the cliffs. They found deposits of highly reactive chemicals like calcium, iron, and magnesium in the slag. These chemicals seem to have sped up rock formation processes. The reactions between the slag materials, air, and ocean generate brucite, calcite, and goethite; these are a kind of natural cement. They are also the same things that link sedimentary rocks in nature.
"For a couple of hundred years, we've understood the rock cycle as a natural process that takes thousands to millions of years," said first study author Dr. Amanda Owen of the University of Glasgow. The rock cycle as it has typically been understood is outlined in the video below.
"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. 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."
There were modern materials like a coin from 1935 and drink tab trapped in these rocks, showing how quickly the rock formation, or lithification, had happened. They estimated that it had taken as little as 35 years for some of this rock to form.
"Slag contains all the elements it needs to turn into rock when it is exposed to seawater and air, so I think it's very likely that this same phenomenon is happening at any similar slag deposit along a relatively exposed coastline with some wave action anywhere in the world," added senior study author Dr. David Brown, also of the University of Glasgow.
Sources: University of Glasgow, Geology
