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City-Strata of the Anthropocene

Published online by Cambridge University Press:  05 March 2020

Jan Zalasiewicz
Affiliation:
School of Geography, Geology, and the Environment, University of Leicester, LE1 7RH
Colin Waters
Affiliation:
School of Geography, Geology, and the Environment, University of Leicester, LE1 7RH
Mark Williams
Affiliation:
School of Geography, Geology, and the Environment, University of Leicester, LE1 7RH

Abstract

The fabric of a city represents a transformation of raw geological materials into a complex assemblage of new, human-made minerals and rocks such as steel, glass, plastics, concrete, brick, and ceramics. This activity has been considered in terms of an “urban metabolism,” with day-to-day inflows and outflows of people, food, water, and waste materials. Here we adopt a longer time-scale spanning years to millennia, related to geological time-scales but still meaningful for present and future generations of humans, and consider cities as sedimentary systems. In natural sedimentary systems, flows of materials are governed by natural forces such as climate and gravity, and leave physical records in, for instance, river-strata. In cities, the flows of geological materials needed for construction and reconstruction are directed by humans, and are largely powered by the fossil energy stored in hydrocarbons rather than by gravity or the sun. The resultant assemblages of anthropogenic rocks and minerals may be thought of as sedimentary (and/or trace-fossil) systems that can undergo fossilization and now exist on a planetary scale. Far more diverse than natural geological strata, they are also evolving much more rapidly, not least in terms of their growing waste products. Considering cities through such a perspective may become increasingly useful as they come to be influenced by, and need to adapt to, the changing conditions of the emerging Anthropocene epoch.

Type
The Anthropocene
Copyright
© Éditions EHESS 2019

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Footnotes

This article was originally published in French as “Les strates de la ville de l’Anthropocène,” Annales HSS 72, no. 2 (2017): 329–51.

References

1 The logic behind this process is outlined in Zalasiewicz, Jan, The Earth after Us: What Legacy Will Humans Leave in the Rocks? (Oxford: Oxford University Press, 2008)Google Scholar.

2 A concise history of the concept of the Anthropocene is given in Will Steffen et al., “The Anthropocene: Conceptual and Historical Perspectives,” in “The Anthropocene: A New Epoch of Geological Time?” ed. Mark Williams et al., thematic issue, Philosophical Transactions of the Royal Society A 369, no. 1938 (2011): 842–67. The two key papers launching the concept in its modern sense are Crutzen, Paul J. and Stoermer, Eugene F., “The ‘Anthropocene,’Global Change Newsletter 41 (2000): 1718Google Scholar; and Crutzen, Paul J., “Geology of Mankind,” Nature 415 (2002): 23CrossRefGoogle ScholarPubMed.

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10 See the report by UN-Habitat: http://unhabitat.org/urban-themes/energy/.

11 Most popular articles on the Anthropocene make heavy use of city images, for instance Kolbert, Elizabeth, “Enter the Anthropocene: Age of Man,” National Geographic, March 2011, 6085Google Scholar. The first two volumes produced by the Anthropocene Working Group have also used city images for their covers, the first by day and the second by night: Williams, Market al., eds., “The Anthropocene: A New Epoch of Geological Time?” thematic issue, Philosophical Transactions of the Royal Society A 369, no. 1938 (2011)Google Scholar; Waters, Colin N.et al., A Stratigraphical Basis for the Anthropocene? (London: Geological Society of London, 2014)CrossRefGoogle Scholar. The cityscape of Shanghai appeared on the cover of the first stratigraphical analysis of the Anthropocene: Zalasiewicz, Janet al., “Are We Now Living in the Anthropocene?GSA Today 18, no. 2 (2008): 48.CrossRefGoogle Scholar

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20 This is discussed in detail in Matt Edgeworth, “The Relationship between Archaeological Stratigraphy and Artificial Ground and Its Significance,” in Waters et al., A Stratigraphical Basis, 91–108, which argues for the use of the term “archaeosphere” to describe this kind of terrain, contrasting it with what archaeologists term “the natural,” that is, the undisturbed geological strata that lie below.

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22 If one simplifies greatly and combines these with other global datasets, one can arrive at a rough estimate for the total mass of the Earth’s urban areas, including both functional and waste materials. According to one such calculation, this counts for some 11 trillion tons out of a total estimated mass of the Earth’s “physical technosphere” of around 30 trillion tons: Zalasiewicz, Janet al., “Scale and Diversity of the Physical Technosphere: A Geological Perspective,” The Anthropocene Review 4, no. 1 (2017): 922CrossRefGoogle Scholar. This figure implies that, spread out evenly over the Earth’s surface (both land and ocean), our city-material now weighs in at over 15 kilos per square meter. [See also the following, published since the original version of the present article was written: Terrington, Ricky L.et al., “Quantifying Anthropogenic Modification of the Shallow Geosphere in Central London, UK,” Geomorphology 319 (2015): 1534.]CrossRefGoogle Scholar

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26 Thomas Brinkhoff, “Major Agglomerations of the World,” 2017, http://www.citypopulation.de/cities.html.

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28 Even though older cities, such as Paris and London, are in large part made of an intermeshed filigree of Holocene and Anthropocene components, these are often readily distinguishable on the basis of their distinctive materials and artifacts.

29 With excellent air conditioning, at least in the termite-built structures. See Bordy, Emese M.et al., “Advanced Early Jurassic Termite (Insecta: Isoptera) Nests: Evidence From the Clarens Formation in the Tuli Basin, Southern Africa,” Palaios 19, no. 1 (2004): 6878.2.0.CO;2>CrossRefGoogle Scholar

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31 Peter K. Haff, “Technology as a Geological Phenomenon: Implications for Human Well-Being,” in Waters et al., A Stratigraphical Basis, 301–9.

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