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Anne-Sophie Milon 2016

A Legacy of the Technosphere

In the end, the technosphere will be buried deep as any other conglomeration of earthly materials, forming timelines of past eras as patterns on the face of cliff faces. Aided by the illustrations of Anne-Sophie Milon, geologist Jan Zalasiewicz speculates about the underground fate of the technosphere’s debris and the puzzle of technofossils that far-future archaeologists will find when digging up the landfills of the global experiment called Anthropocene.
There is a remarkable rock exposure along the lovely Elan Valley in central Wales, visible as one makes one’s way westwards from the town of Rhayader, toward the bleak (or austerely beautiful, if you prefer) hills of mid-Wales. This singular outcrop makes up almost the whole of a hillside at Caban Coch just outside the town, and you can examine it closely by stopping in the carpark by the first of the several dams that form a string of reservoirs successively up the valley. The carpark, indeed, is in the base of an old quarry from which the rock had been hewn (to make, of course, the dam below). The rock is a conglomerate, an ancient mass of pebbles and sand from the Silurian Period, compressed and cemented together in the intervening 420 million years to make an exceedingly tough material (ideal, indeed, for dam-building). It makes for a layer that is strikingly light-colored in reality, but depicted on the geological map of the district in bright red, to contrast with the greys and greens of the endless slates that otherwise make up this Welsh landscape. As layers go, though, it does not go very far at all. Traced to the next hill along, in both directions, it thins and fizzles out, and the endless slates resume their dominance. Indeed, it is not so much a layer as a giant half-cylinder viewed end-on, an ancient underwater canyon choked with gravelly debris swept off an ancient beach, its silhouette traceable on today’s hillside.
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Anne-Sophie Milon 2016

This classical outcrop of Silurian geology sometimes comes to my mind when I think of the debris of the technosphere, that we sweep out of mind into the canyons of our landfill sites. The scale is similar, for a landfill site may pile up rubbish to a thickness approaching ‒ or exceeding – a hundred meters, and may be kilometers in length and width. Rather like the gravel-filled Caban Coch canyon, they contrast sharply with the sediment layers within which they are embedded – the rubbish of our civilization is often packed within the holes that are gouged into the ground for brick clays, for instance, or building sand. And, rather like the Caban Coch rock, they may endure for hundreds of millions of years, to preserve a narrative far into the future. Let us continue the parallel. The Caban Coch conglomerate, and the ancient geography and processes that it encapsulates, has survived for a span some three times longer than that which separates us from the dinosaurs. It has survived in the safest place on Earth – for a rock, that is – which is deep underground. The first few millions of years were critical. The Silurian canyon, quite simply, was buried by the silts and muds that poured in from the eroding landscape; a brief few million years later, it was some five kilometers below the sea floor, as the muds kept pouring in and piling, their enormous weight alone helping the crust to subside. By that time, heated by the Earth’s inner warmth and compressed by the enormous weight of sediment on top of it, the conglomerate was likely already a rock, the pebbles and sand grains firmly cemented together by subterranean chemical processes. Then – an accident, as the piece of crust the mass was on was involved in a collision with another fragment of crust that today we call Spain. The Welsh mountains rose as a result of the immense forces generated, and for the next 396 million years (we can tell this from radioactive chemistry triggered by that event, which took place around the fossilized remains of tiny planktonic organisms that lived in and around the canyon) the canyon has been inching ever-nearer to the surface, as the mountains above have been eroded away. By another accident of time, this prehistoric canyon happens to be on the Earth’s surface, exposed on the Caban Coch mountainside, right now. Another few million years of erosion might wear it away completely.
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Anne-Sophie Milon 2016

Let us put one of humanity’s huge landfill sites through a similar history. There are enough to choose from, accumulating around every major city – many of which are sited on deltas and coastal plains, regions that are natural sites of crustal subsidence. They are poised, geologically soon, to be deeply buried, as if on a gigantic down-going tectonic escalator, the process being helped by the ongoing rise in sea level. When the escalator reverses, some hundreds of millions of years from now (for argument’s sake let’s give our landfill a similar longevity to our ancient canyon) to expose the landfill site at the surface of some future hillside – and especially, if there is some future geologist, of whatever species, to gaze curiously at it . . . what then? On first appearances, it would seem at least as striking as our Silurian canyon-fill, no matter, almost, what rock would encase it from a distance so that it would appear notably dark, through, not pale-colored, by contrast with the surrounding rock. The rubbish we throw away contains a lot of uneaten food, and also a lot of paper and plastic and wood fragments. All of these are essentially hydrocarbons, and all of it, over the millions of years, underground, will be heated and pressurized (releasing some oil and gas in the process) and converted into blackened carbonized remnants. From a distance, this will likely give the petrified landfill something of the appearance of a short and stubby but monstrously thick coal layer, standing out against the paler rocks of the hillside. Seeing a quite unusual rock type from a distance, a geologist – whether contemporary or in the far future – will want to get closer and see what it is made of. This close look will be challenging. The rubbish that we throw daily into landfill sites contains not just scraps of food and paper and plastic, but also discarded televisions and computers, furniture, toys, cutlery and crockery, chicken bones and vegetable peelings, broken tools, CDs, containers of all sorts, building rubble, clothes, used nappies, ballpoint pens, toothbrushes and‒ almost literally ‒ a million other things. There is more here to examine and analyze than there is in a mass of pebbles and sand.
This is not to denigrate pebbles and sand: properly interrogated, these sedimentary particles can tell all kinds of tales about the world of the past. But the cast-offs of the technosphere bring with them a whole new dimension of geological complexity.
First off – how much might remain to interrogate? Among ancient fossils, there is a huge range in fidelity of preservation, from rough imprints on rock surfaces that include no useful detail, to almost perfect preservation of complex biology, right down to details of cellular structure. The reason for this enormous range is all down to the length of time a dead animal and plant stayed on the surface, where it is subject to scavenging and decay, and also to the chemical environment, the remains subsequently underground, as they are buried in strata. While some environments promote dissolution and dispersal of complex biological material, others petrify them within armor-layers of newly precipitated minerals. So how might the complex structures of our discarded technology fare? It is both fascinating puzzle and global experiment rolled into one. The burial part is easy – a modern, well-regulated landfill site will quickly bury objects far out of the reach of scavenging seagulls and rats and earthworms. But what then? Here the sheer variety of the materials tipped into a landfill site should offer a huge range of preservation environments, all depending on particular local subterranean micro-conditions. Consider, say, a digital wristwatch, a commonplace technological marvel of modern times, discarded once its battery has run out because it is cheaper to buy another watch than replace the battery. Like most other objects in the landfill, it will be within one plastic bag (like the one in your kitchen bin) and then within a larger structure, the plastic sheets put in by the landfill operators to isolate the rubbish from the local environment.
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Anne-Sophie Milon 2016

This kind of ultra-compartmentalization will guarantee myriad microenvironments, each providing a different underground fate and form to all of the buried objects. Placed in a bag with discarded food, the watch will soon stew in acid leachate, and may corrode away completely. However, if placed together with some discarded plaster or concrete mix, it could rapidly become encased in newly crystallized calcium carbonate (just like, say, superbly preserved fish fossils from Jurassic times). This calcium carbonate armor can preserve fine details of the shape in outline of its tiny machinery, even though, over millions of years, some of the metals might leak, atom by atom, away into the surrounding rock. If the watch falls into some discarded tar spilt from a half-empty tin tossed into the waste, then even this information-loss might be stopped, so that the microtechnology is carried into the far future, as insects from the times of the dinosaurs are preserved, when encased in amber, to the present day. The far-future paleontologists who will (we will assume) reconstruct, from these infinitely variable petrified remnants, the technosphere built by humans, will move, inch by inch, across these fossilized landfills, as not only the objects but also their aspects change their nature, centimeter by centimeter. A square meter might include such complexity and variety as to provide work for a lifetime of such study. One can almost envy our distant imagined successors the puzzles that will consume them, the hypotheses they will generate, the care and patience they will need to extricate the most beautifully preserved fragments from the unforgiving rock. The long view of deep time has its consolations. When one is in the middle of a revolution, perhaps contemplation of a distant aftermath, by then detached from the forces that drove it, might provide some perspective. That perspective can show us, by comparison with ancient strata, that what is going on now is something truly new and remarkable. But whether that perspective can usefully help us guide the forces driving the hyper-rapid evolution of the technosphere in the tumultuous here and now . . .? Well, that is quite another question.