From the Soil to the Sky
Elise Misao Hunchuck writes to Montserrat Bonvehí Rosich
This text is a response to Montserrat Bonvehí Rosich’s letter to Elise Misao Hunchuck.
Dear Montserrat, your questions have been haunting me because they ask for nothing less than a complete reversal of how we understand urban temporality. When you contemplate whether cities host their past lives under our feet, you’re not only asking about archaeology or design, you’re asking—if not encouraging—us to understand cities (and any and everywhere we inhabit) as temporal compost systems, spaces where past forms of life decompose to feed whatever emerges next.
This is a necropolitical question as much as an ecological one. Every city is built on the decomposed dreams of its previous inhabitants, the material breakdown of obsolete social relations, the nutritive remains of sometimes abandoned, sometimes destroyed, ways of life. Your technosol example in Mexico City contains not just earthquake debris, but one could say, the collapsed aspirations of 1980s urban planning, the remains of modernist confidence, and the chemical breakdown of social forms that no longer function.
When I think about the planned decomposition process that you described—catastrophic sedimentation becoming productive soil1—I think about paleotsunami deposits I encountered in 2015 (the same year you photographed the Mexico City excavation), and I realise they represent a similar process at a different temporal scale: the violent composting of an entire way of coastal living, the transformation of human settlement into substrate for whatever marine-terrestrial ecology might emerge from such disruption.
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The process, as you described it, is instructive in its precision: 1.6 million cubic metres of concrete, red brick, and asphalt from the September 19, 1985 earthquake, compacted to 2.5 to 3 metres thickness, capped with 20 centimetres of tepetate clay, then thin topsoil, then decades of regular composting. Thirty years of weathering, microbial action, and the accumulation of organic matter transformed otherwise sterile rubble into fertile substrate. This is planned decomposition on an urban scale—catastrophic sedimentation becoming productive soil through designed temporal processes. ↩
In July of 2015, I was walking under a blistering summer sun in Onagawa, along one of the few open, accessible roads that led uphill from what used to be the town centre. To my right rose the steep, forested mountains that had amplified the force of the Great East Japan Earthquake and tsunami of 2011.1 To my left, behind a wire fence, was where the centre of the town of Onagawa—one of the most damaged settlements during the disaster—used to be. It was mostly cleared of itself, scraped of surficial debris. Heavy digging machinery was parked here and there across the terraformed expanse. I was looking for a tsunami stone, a monument-marker, when I came upon a construction trench beside the road.
Inside the cut of that trench, interrupting the expected stratigraphy of brown aggregates, was a shocking layer of black ooze that seemed, somehow, still wet four years after the disaster. I wouldn’t know until later that afternoon that I was looking at a paleotsunami deposit2, the heavy organic sludge that remains after a tsunami retreats, the decomposed traces of communities, liquefied and ready to feed new forms of coastal existence.
These paleotsunami deposits demonstrate nature’s own method of catastrophic recomposition: layers of coarser sand interrupting the fine-grained continuity of marsh sediments, anomalous materials like salt crystals, plant remains, and shells all pressed into organic sludge by waters that moved with the force of continents.3 Where one might expect orderly accumulation—the patient deposits of tidal cycles, the gentle settling of river silts—instead appears the violent signature of a single event: marine and terrestrial worlds suddenly converged, their combined detritus becoming the foundation for whatever plant communities can eventually establish on such mixed substrates.
Standing beside that trench, looking down at that black layer, I was witnessing the same process you document in Mexico City: urban catastrophe becoming geological stratum, the built environment returning to substrate, past lives decomposing beneath the surface to feed whatever might grow next.
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In English, the Tōhoku earthquake of 11 March, 2011 is often translated as the “Great East Japan Earthquake.” However, its original name is Higashi Nihon Daishinsai, which means East Japan Great Earthquake Disaster. Daishinsai (earthquake disaster), is not the same as jishin (earthquake), as daishinsai holds within it both the tsunami as well as the damage caused by the Fukushima nuclear power plant crisis (which occurred shortly after the earthquake-tsunami event). ↩
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I must thank Univ.-Prof. Dr. Klaus Reicherter (RWTH Aachen University) for answering my tweet that same day, confirming my suspicions that it was, in fact, a paleotsunami deposit, and for, many years later, in 2025, inviting me to join his research team to go back to Japan and carry out more field work in Honshu and Hokkaido. ↩
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It is recorded that the force of the 2011 earthquake moved the Earth’s axis by approximately 17 centimetres, it moved the main Japanese island of Honshu by about 2.4 metres to the east, and slightly sped up the Earth’s rotation, shortening the length of a day by 1.8 microseconds. Figures reported by Kenneth Chang in “Quake Moves Japan Closer to U.S. and Alters Earth’s Spin” in The New York Times on 13 March, 2011. ↩
The Aketo seawall in Tanohata village (田野畑村, Tanohata-mura), seen here in September 2024, was destroyed in the Great East Japan Earthquake Tsunami of March 11, 2011. Video courtesy Marco Ferrari and Elise Misao Hunchuck (2024).
But there is a third form of recomposition—one that emerged not from a single event but from the slow-motion of urban growth itself. Extending five kilometres into Lake Ontario from Toronto’s harbour lies what planners have termed an “accidental wilderness” previously known as the Leslie Street Spit, now Tommy Thompson Park. Close to 9.5 million cubic metres of various materials were used to create the land, including rubble and debris from old buildings and subway construction.1
If paleotsunami deposits in Onagawa represent the convergence of marine and terrestrial worlds, and the earthquake debris in Mexico City embodies the collision of vertical and horizontal forces, then Toronto’s constructed substrates document the ongoing collision of urban metabolism with geological time. Researchers discovered that the spit is not only comprised of construction waste, but it is literally built from Toronto’s past—household items like teacups, medicine bottles, eyeglasses, and old toothpaste tubes in sections created in 1964, along with bricks from homes demolished in the 1960s and rubble from nineteenth-century row houses. Toronto’s anthropogenic sediments record the continuous catastrophe of urban development, decades of accumulated demolition stratified into substrates that should not exist.
These three sites reveal different temporal scales of the same process. Yet all three became, unexpectedly, fertile ground. The thirty-year timeline for technosol formation parallels how plant communities eventually colonize paleotsunami deposits, slowly transforming emergency geology into productive substrate. But Toronto offers a radically different temporal model. The botanical colonization happened almost immediately. It is thought that the first cottonwoods grew from light-tufted seeds carried by the wind from the nearby Toronto Islands. Already by 1976, a few saplings had attained six metres; by 1982, some trees reached 11 to 13 metres—a rate of succession unusually rapid compared to similar scenarios in eastern North America, suggesting the heterogeneous construction debris created an optimal pioneer habitat. We might say that Tommy Thompson Park represents the ongoing decomposition of urban domesticity itself.
The alkaline chemistry of concrete, the excellent drainage of brick rubble, the seasonal water retention created by impermeable surfaces—all the material properties that made this “waste” problematic from a conventional soil perspective made it productive from an ecological one. Due to the nature of construction and substrates, Tommy Thompson Park is somewhat impervious to water infiltration. The consequence is, in some areas, standing surface water that creates seasonally wet areas that are highly attractive to a variety of wildlife. Today, over 330 bird species now inhabit landscapes fed by the breakdown of mid-century Canadian urban life, their nests built from the nutritive remains of demolished neighbourhoods.2 The violent mixing of materials that should remain separate, creating unexpectedly fertile conditions for new ecologies. The earthquake in Mexico City mixed decades of the city’s built fabric into stratified substrate. The Onagawa deposit mixed marine and terrestrial worlds into organic sludge. Toronto’s ongoing urban metabolism mixed construction debris across multiple eras into highly variable soil.3 The moment of recognition was similar in all three cases—the sudden realization that what appeared to be waste, disaster, or sterile substrate was actually a generative geological event in progress.
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The Leslie Street Spit was constructed starting in 1959 by Toronto Harbour Commission as a breakwater for expanded shipping operations. Built from construction debris and including three capped containment cells for toxic materials, the planned harbor expansion never materialized due to changing shipping patterns. By the early 1970s, natural vegetation had colonised the site which would come to be known as Tommy Thompson Park in 1984, named after the first park commissioner of the city of Toronto. ↩
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For more on the bird counting and bird research stations in Tommy Thompson Park, see: https://trca.ca/news/tommy-thompson-park-bird-research-station/ ↩
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Highly variable soils are soils where physical, chemical, or biological properties—texture, pH, nutrient levels, microbial communities—shift unpredictably across space. These differences aren’t just variations: they’re discontinuities that affect how the soil behaves, what it can support agriculturally, and how it responds when environmental conditions change. The variability isn’t uniform or mappable in any simple sense; it’s a kind of spatial instability that resists easy categorization. In this case, the soils support, in close proximity, meadows, poplar forests, meadow marshes, sand dunes and beach/bar communities. ↩
From the overgrowth of Tommy Thompson Park, the horizon of the city of Toronto is seen through a haze of black carbon, the result of hundreds of forest fires burning in the summer of 2025. Video courtesy Elise Misao Hunchuck (2025)
But Montserrat, your second question is even more radical: How should we build our cities if we think about them as future layers of a more fertile soil profile? You’re asking us to design with geological conscience—to build cities that are already anticipating their own productive decomposition.
What would it mean to plan obsolescence as ecological gift? Instead of designing for permanence, we would design structures with optimal decomposition trajectories—buildings that break down into the most nutritious substrates for post-human ecologies. But soil formation is only half the story. The convergence of terrestrial and oceanic worlds in those paleotsunami deposits makes me think about a third layer: the atmospheric.
Our landscapes of hope aren’t just beneath our feet—I think they’re also in every breath we take. What materials become in the soil is inseparable from what they release into the air throughout their lifetimes. Construction debris immediately supporting diverse plant communities while simultaneously creating new atmospheric conditions through the slow release of mineral compounds, the off-gassing of decomposing organic matter, the creation of microclimates where different air chemistries emerge. I keep thinking about temporal stratification—how every urban intervention we make today becomes both a future soil horizon and a future atmospheric condition. The concrete we pour becomes not just the alkaline layer that future plant communities will adapt to, but also the source of mineral dusts, pH-altering aerosols, the slow atmospheric release of embedded carbon. What if we chose building materials not just for their eventual soil chemistry but for their atmospheric gifts?
All three sites in Mexico City, Onagawa, and Toronto created new atmospheric conditions alongside their novel soils. The paleotsunami deposits don’t just provide substrate—they release salt aerosols that create coastal microclimates, influence local precipitation patterns, change the very air that moves inland from the sea. The earthquake technosol isn’t just becoming fertile ground—it’s creating new patterns of soil respiration, new relationships between earth and sky as organic matter decomposes and releases gases that feed atmospheric cycles. The bird communities in Tommy Thompson Park aren’t just nesting in constructed soils—they’re breathing air that’s been filtered through novel plant communities growing on construction debris, air whose chemistry has been altered by the slow release of compounds from decomposing brick and concrete, air that carries the pollen and spores of plants that could only exist on such substrates.
What if we chose materials that improve air quality as they age? That release beneficial compounds into the atmosphere as they weather? That create microclimates conducive to the atmospheric needs of post-human ecologies? This isn’t about returning to entirely natural materials, but about understanding that every material choice is simultaneously a soil choice and an air choice, a decision about what future atmospheres we’re creating for whatever breathes with us—and long after us.
Our landscapes of hope ask us to build backwards from the soil, to start with the question of what kind of substrate we want to leave for future ecologies, and to design cities that will decompose into exactly those conditions. All three sites demonstrate this is already happening. We just need to make it intentional. This is not mere sustainable urbanism. This is necro-ecological urbanism, building cities that are already dead, already becoming soil, already feeding the post-human futures growing beneath our feet and up, into the sky.
p.s. Since writing this letter in September 2025, researchers excavating Toronto’s re-naturalized Don River—just a few kilometres from Tommy Thompson Park—have published their discovery that industrial burial doesn’t destroy substrates. It suspends them. Century-old wetland soils, entombed under seven and a half metres of fill since the 1890s, released living water fleas, worms, larvae, and zooplankton when submerged in water—micro-ecosystems that resumed feeding, moving, spinning after waiting 130 years. The soil was, as one researcher, Shelby Riskin described it, ready to turn on. Cryogenics without the cold. Entire communities of life preserved by the pressure and chemistry of accumulated catastrophe. This reveals the mass-regeneration potential beneath our cities: catastrophic sedimentation moves in both directions. Cities don’t merely decompose forward into future ecologies. They hold past ecologies in stasis, dormant systems waiting for exposure to reverse burial into resurrection. Urban substrates are temporal archives where life doesn’t end—it pauses, ready to continue the moment conditions allow.