Jun 17, 2026 05:46 PM
https://aeon.co/essays/the-strange-rocks...without-us
EXCERPTS: As a geologist, I have studied various types of natural rocks, but recently I have become interested in ‘anthropogenic geomaterials’ – things like industrial slag – and how they become entwined in geological and environmental processes. I came to Workington originally to look at the slag...
[...] For geologists who study rock day in day out, it’s such a foundational concept that we rarely stop to ask what’s the actual definition of a rock. So I quizzed a few, in a non-statistical, non-exhaustive informal survey of geological friends and colleagues. When asked, hardness featured heavily in people’s definitions, and most agreed that a rock is a substance made of minerals. There was less agreement with the dictionary when it came to size though – the OED and Cambridge definitions point to rock being a large mass or even the whole Earth, but some geologists would argue that a grain of sand could be considered a rock. It is, after all, hard and made of minerals, like quartz or feldspar.
Perhaps the most debated part of the definition, and the one most relevant to this essay, is whether a rock must be natural. The overwhelming majority of rocks on Earth form through natural geological processes such as solidification of molten lava flows, or compression and compaction deep within the Earth. However, everyday materials created by humans such as pottery, concrete or bricks are made of minerals. Are these rocks? Many would say not. Perhaps that’s because these materials are processed, manufactured, and more often found in the built environment rather than in wild landscapes. As we discovered at Workington, though, the border between natural and human is more difficult to draw.
If you were to tell anybody about a pile of thousands of tonnes of industrial waste, most people’s reaction would probably be to recoil in disgust. In many cases this holds true, such as when old landfills of municipal waste are exposed through coastal erosion, resulting in old rags, sanitary products and medical waste leaking onto coastlines. There’s something about a wet muddy bit of fabric on the beach that just gives you the ‘ick’. However, the vast majority of visitors to a place such as Workington would be none the wiser that they were in the proximity of a huge volume of industrial waste.
[...] Human beings have created slag for thousands of years, ever since people started working with metals. While in the past it was simply dumped, today the material is often reused in other settings, such as cement production, road construction, agriculture, or along railway lines as ballast.
[...] Once the slag that makes the cliff was poured and solidified, human involvement in the story ends. Workington is quite an exposed coast, with storms rolling in over the Irish Sea. The waves crashing against the slag cliffs causes them to erode – just like natural coastal cliffs – chipping off small, angular pebble-sized pieces. The wave and tide action then rounds off the corners.
[...] Anthropogenic rock formation is a frontier research area with relatively few examples documented. However, once we understood what was going on at Workington, we were able to identify the same process occurring in other places where iron and steel slag had been dumped historically, with examples in northern England and southwest Scotland. We also started to find evidence of ‘rocks’ forming from other human-made materials, or where human processes had been key.
[...] Geologists are also learning that the more ‘solid’ examples of industrial waste can actually bring many benefits. Slag has carbon dioxide mineralising properties – essentially scrubbing CO2 out of the atmosphere, giving it the opportunity to help us in our fight against anthropogenic climate change. Additionally, old slag banks are known to be havens for rare species of plants and invertebrates – their gravelly and alkaline nature makes them an unusual habitat. However, if the gravelly slag has fused together into a rock, it may be more difficult for ecological colonisation. The study of such anthropogenic materials is a frontier area of research and there remain many unknowns.
In our discipline, we geologists are used to looking back into the distant past, perhaps to learn lessons about what our geological future might look like. With these anthropogenic rocks it is difficult to do this, as no ancient analogues exist... (MORE - missing details)
EXCERPTS: As a geologist, I have studied various types of natural rocks, but recently I have become interested in ‘anthropogenic geomaterials’ – things like industrial slag – and how they become entwined in geological and environmental processes. I came to Workington originally to look at the slag...
[...] For geologists who study rock day in day out, it’s such a foundational concept that we rarely stop to ask what’s the actual definition of a rock. So I quizzed a few, in a non-statistical, non-exhaustive informal survey of geological friends and colleagues. When asked, hardness featured heavily in people’s definitions, and most agreed that a rock is a substance made of minerals. There was less agreement with the dictionary when it came to size though – the OED and Cambridge definitions point to rock being a large mass or even the whole Earth, but some geologists would argue that a grain of sand could be considered a rock. It is, after all, hard and made of minerals, like quartz or feldspar.
Perhaps the most debated part of the definition, and the one most relevant to this essay, is whether a rock must be natural. The overwhelming majority of rocks on Earth form through natural geological processes such as solidification of molten lava flows, or compression and compaction deep within the Earth. However, everyday materials created by humans such as pottery, concrete or bricks are made of minerals. Are these rocks? Many would say not. Perhaps that’s because these materials are processed, manufactured, and more often found in the built environment rather than in wild landscapes. As we discovered at Workington, though, the border between natural and human is more difficult to draw.
If you were to tell anybody about a pile of thousands of tonnes of industrial waste, most people’s reaction would probably be to recoil in disgust. In many cases this holds true, such as when old landfills of municipal waste are exposed through coastal erosion, resulting in old rags, sanitary products and medical waste leaking onto coastlines. There’s something about a wet muddy bit of fabric on the beach that just gives you the ‘ick’. However, the vast majority of visitors to a place such as Workington would be none the wiser that they were in the proximity of a huge volume of industrial waste.
[...] Human beings have created slag for thousands of years, ever since people started working with metals. While in the past it was simply dumped, today the material is often reused in other settings, such as cement production, road construction, agriculture, or along railway lines as ballast.
[...] Once the slag that makes the cliff was poured and solidified, human involvement in the story ends. Workington is quite an exposed coast, with storms rolling in over the Irish Sea. The waves crashing against the slag cliffs causes them to erode – just like natural coastal cliffs – chipping off small, angular pebble-sized pieces. The wave and tide action then rounds off the corners.
[...] Anthropogenic rock formation is a frontier research area with relatively few examples documented. However, once we understood what was going on at Workington, we were able to identify the same process occurring in other places where iron and steel slag had been dumped historically, with examples in northern England and southwest Scotland. We also started to find evidence of ‘rocks’ forming from other human-made materials, or where human processes had been key.
[...] Geologists are also learning that the more ‘solid’ examples of industrial waste can actually bring many benefits. Slag has carbon dioxide mineralising properties – essentially scrubbing CO2 out of the atmosphere, giving it the opportunity to help us in our fight against anthropogenic climate change. Additionally, old slag banks are known to be havens for rare species of plants and invertebrates – their gravelly and alkaline nature makes them an unusual habitat. However, if the gravelly slag has fused together into a rock, it may be more difficult for ecological colonisation. The study of such anthropogenic materials is a frontier area of research and there remain many unknowns.
In our discipline, we geologists are used to looking back into the distant past, perhaps to learn lessons about what our geological future might look like. With these anthropogenic rocks it is difficult to do this, as no ancient analogues exist... (MORE - missing details)
![[Image: CI1TDJ4.jpg]](https://iili.io/CI1TDJ4.jpg)