Unprecedented planetary change in a human lifetime?

Humans have been seen as active geological agents on our planet since the earliest days of our science. But the concept of the Anthropocene really took hold as the Earth System Science and Global Change (ESS) communities began to grasp the unprecedented speed and scale of environmental change driven by the collective activities of industrialised humanity. Realising this, and frustrated that his colleagues were still using the term Holocene to refer to the present, the atmospheric chemist and Nobel laureate Paul Crutzen made a now-famous intervention at a meeting of the International Geosphere-Biosphere Programme in 2000. “We’re not in the Holocene anymore”, he burst out, “We’re in the … Anthropocene”.

This improvised term and the Anthropocene concept quickly took root in the ESS communities, becoming widely used and published as a de facto epoch to describe these current, transformed, planetary conditions. But is there a chronostratigraphic basis for the Anthropocene? Have human activities altered the functioning of our planet to such an extent that they have left a synchronous, indelible, globally recognisable archive in the geological record – strata that chronicle a substantial and rapid shift in planetary process away from those typical of the Holocene, such that they call for formal recognition as a separate epoch in the geological timescale?

If so, when precisely did this epoch begin? The Anthropocene was initially associated with the onset of the Industrial Revolution in the UK in the late 18th century (Crutzen, 2002). However, the concept of a ‘Great Acceleration’ of fossil-fuelled industrialisation and globalisation that profoundly and rapidly changed physical, chemical, and biological processes on Earth from the mid-20th century was also emerging, and was soon seen as the most optimal start of the Anthropocene (Steffen et al., 2015, updated from earlier work). Here we discuss some of the stratigraphic evidence supporting the idea that the Anthropocene does warrant formalisation as an epoch, and one that did indeed begin in the middle of the last century.

Regardless of how we name it, the Anthropocene has already irreversibly set the Earth System on a new course with many consequences, some of which reach into the heart of our science

A geological reality

Recognition that dramatic human-induced changes could amount to the termination of the Holocene was first considered geologically by the Geological Society’s own Stratigraphy Commission in 2008 (Zalasiewicz et al., 2008). This led to an invitation to set up the Anthropocene Working Group (AWG) as a task group of the Subcommission on Quaternary Stratigraphy. From 2009, the AWG has investigated the potential of the Anthropocene as a formal geological time unit, and therefore a new interval of the International Chronostratigraphic Chart as maintained by the International Commission of Stratigraphy (ICS). For formal recognition as an epoch, strata formed during the Anthropocene would need a clearly recognisable base, defined via a reference point within a stratigraphic section that marks the lower boundary and beginning of the new geological unit, a so-called Global Boundary Stratotype Section and Point (GSSP), informally termed a ‘golden spike’.

The AWG, the first truly multidisciplinary task group of the ICS, examined the stratigraphic evidence of human activity while also exploring humanities-linked perspectives – appropriate given the Anthropocene’s overlap of geological and historical time. What the AWG found was striking evidence that the Anthropocene does indeed possess geological reality consistent with a formal, chronostratigraphic epoch (Zalasiewicz et al., 2017).

The AWG could not identify a consistent, correlatable boundary associated with the early Industrial Revolution, because the course of the industrialisation, and the regional signals it generated, took place at different times in different parts of the world. However, an effective boundary could be placed in stratigraphic successions spanning the mid-20th century, reflecting the transformational, more globally synchronous planetary changes caused by the Great Acceleration (Syvitski et al., 2020, 2022). These changes, having no precedent in the Holocene, subsequently guided the AWG’s analyses towards proposal of a formal GSSP.

The Great Acceleration is characterised by unprecedented levels of production and waste materials consequently finding their way into stratigraphic successions worldwide, including landfill sites containing novel synthetic materials (© iStock)

The Great Acceleration is characterised by stratigraphic successions worldwide spanning the latter half of the last century that contain a glut of stratigraphic markers including novel synthetic materials, and evidence of ecological disruption and mass perturbation of Earth’s major element cycles (Zalasiewicz et al., 2019; Williams et al., 2022). Many are specific to the technological, consumerist changes seen since the 1950s, such as the mass-use of plastic and concrete, and the mass production of technological artefacts, including vehicles, weapons, and computers (becoming preserved as technofossils). Others are due to fossil fuel burning, such as spheroidal carbonaceous particles (a distinctive type of fly ash only produced by power stations) that have their origin in the 19th century but showed accelerated rates of production and deposition in the mid-20th century, and a pronounced carbon isotope anomaly already being imprinted in carbonate, shell and wood. Some reflect landscape modification (such as urbanisation and dam building), with anthropogenic sediment consumption having increased 2,000% since 1950 and anthropogenic exceeding natural sediment flux >15-fold (Syvitski et al., 2022). Others reflect the intensification and industrialisation of agriculture (to feed a population that increased from ~2.5 billion in 1950 to around 8 billion currently), marked by the appearance of novel persistent organic pollutants found in pesticides and mass use of fertiliser (recorded as both raised and isotopically altered nitrogen and phosphorus levels), as well as anoxic ‘dead zones’ recorded in sedimentary successions. Not least, the unique historical, geopolitical circumstances of the 1950s resulted in above-ground thermonuclear bomb testing introducing radionuclide markers near-synchronously into global stratigraphic successions. Such a time boundary, occurring in the last 75 years, therefore combines routine deep-time stratigraphic procedure with the historical, political, social, and environmental disciplines used to understand our planet and its inhabitants.

The Stausee Mooserboden Dam, Kaprun, Austria. The construction of ~58,000 large dams since the mid-20th century (a rate of about two per day) has radically modified global river systems reducing river sediment flux to the oceans by 46% in 60 years, with immediate potential flooding impact on the more than 300 million people living on the sedimentstarved great deltas of the world already at risk of subsiding under rising sea-levels (© iStock)

Global synchronicity

The geological investigations to select a succession that defines a chronostratigraphic boundary for the base of the Anthropocene took place alongside a collaborative exploration of their cultural, social and artistic implications by the Haus der Kulturen der Welt in Berlin – which had secured funding to contribute to the analysis – and the Max Planck Institute of the History of Science (Rosol et al., 2023; anthropocene-curriculum.org). The AWG fostered relationships with scientific teams already working on annually resolvable successions from many environmental archives. The ability to identify a precise year in a stratigraphic succession is unique in the history of GSSPs but was sought here due to the merging of calendar and geological timescales in the Anthropocene.

The AWG assembled an array of 12 globally distributed sites in different depositional settings to explore the synchronicity, variability and diversity of the stratigraphic markers (Waters et al., 2023; Fig. 1). Successions were sought that had continual sedimentation not only spanning the mid-20th century but also ranging further back in time and into the present.

Figure 1: Map of sites. Anthropocene successions were intensively studied at 12 sites across the globe. (Image credits: 1) A. Stegner; 2) S. Himson; 3) L. Thomas; 4) K. DeLong; 5) F. McCarthy; 6) M. Wagreich; 7) A. Borsato; 8) B. Fiałkiewicz-Kozieł; 9) J. Kaiser; 10) Y. Han; 11) M. Kuwae; 12) J. Zinke)

Since its geological analysis began, the Anthropocene has triggered fierce controversy

As well as obtaining materials available for analysis, it was also necessary to secure an intact, safely archived portion of the proposed stratotype to be available for future study (here a precedent existed with the Holocene stages: Greenlandian, Northgrippian ice core sections and the Meghalayan speleothem). The successions explored provide effective records of interacting geological and human processes across this transformative interval. Ranging in thickness from 4 mm to 34.9 m, the Anthropocene successions record major planetary change in great detail.

Two marine successions were studied: from the East Gotland Basin in the Baltic Sea and Beppu Bay, Japan. In both successions, the Anthropocene onset is approximated by a clear lithological change, as dark organic-rich laminated sediment follows pale, burrowed sediment, reflecting increased eutrophication and sediment anoxia caused by agricultural and industrial pollution. The Beppu Bay’s fine-scale stratigraphy was deciphered by recognising annual varves and turbidite/tempestite layers from historical floods, typhoons, and earthquakes. Just under a hundred kinds of stratigraphic proxy were measured and correlated. Many begin, or show marked changes, in the early 1950s, reflecting dramatic land-use change from rapid industrialisation and urban growth.

From more sunlit waters, two coral cores were investigated that preserve detailed records from the 18th century to the present: from Flinders Reef, off the Queensland coast, Australia, and West Flower Garden Bank in the Gulf of Mexico, off the coast of Texas, USA. These are some of the most highly resolved records of all: from both sites, the scientific teams sampled consecutive seasonal growth layers for contaminants throughout the cores. They contain many proxies (such as nitrogen, carbon, and oxygen isotopes) of changing seawater properties, while the most striking Anthropocene signal is a dramatic and precisely correlatable radiocarbon ‘bomb’ spike.

Two sites lie near San Francisco, California: estuarine mud cores from the middle of the South Bay and a core from Searsville Lake, Stanford, a reservoir constructed in 1892 CE. Both illustrate historic human impacts on erosion and sedimentation. San Francisco Bay represents an ecosystem highly modified by industrialisation and urbanisation runoff, and by the introduction of waves of non-native species brought in by shipping, the fossil remains of which provide high-resolution biostratigraphic markers (Williams et al., 2022). The thick Searsville Lake succession results from enhanced soil erosion over the last century. Its annual layers reflect strongly seasonal rainfall, and reveal many time-markers such as from historical applications of copper-sulfate as an algaecide, and seismic disturbance to the sediments during the major 1906 and 1989 earthquakes.

Representation of the mid-20th century in archaeological layers was explored in urban soils exposed during excavations at the Karlsplatz, Vienna, Austria. 19th century layers associated with parklands, urban development and river flooding are overlain by the foundations of an early 20th century hall, demolished and abandoned during World War II, and by further soil layers as the area became developed as the Wien Museum. The World War II rubble contains distinctive technofossils from the war, while overlying soil layers from the mid-20th century contain the global signature of radionuclides, the fallout from aboveground nuclear bomb testing. Significant gaps in deposition made this site unsuitable as a GSSP, but it is still an intriguing reference section.

The underground realm was also studied, following the precedent of a speleothem used to define the GSSP of the Meghalayan Stage of the Holocene (4.2 ka BP at ~7 mm depth). In Ernesto Cave, Italy, the Anthropocene Epoch is contained within ~4 mm of a sectioned stalagmite, in which annual couplets of calcite layers (where darker organic-rich layers form in autumn) include signals of industrialisation such as sulphur isotopes, and also bomb radiocarbon (although these signals were delayed and attenuated by their travel through soil and bedrock before arriving at the growing stalagmite tip). The stratigraphic record here is faithful – but lags the actual events by a decade or two.

By contrast, the ombrotrophic peat sequence (one that receives all its nutrients from rainfall) analysed from near the summit of Śnieżka Mountain in Poland contains an immediately registered and well-resolved archive of European and global atmospheric markers of the mid-20th century. The growing ombrotrophic peat acted as a trap for plutonium isotopes from nuclear weapons testing, fly ash particles, heavy metal aerosols, and pollen, including from non-native species.

The global ubiquity of Anthropocene markers can be seen in even the most remote places, notably the Palmer ice core from Antarctica. Its annual layers show methane concentrations rising from the Industrial Revolution and then yet more sharply at the proposed Anthropocene boundary, and also include traces of plutonium. Extraordinarily, some fly ash particles were detected too, windblown across the Southern Ocean to accumulate in the snow.

Palaeolimnological perfection

In all, the AWG acquired an embarrassment of stratigraphic riches (Waters et al., 2023). Many of the sites summarised above could have formed an effective GSSP – but only one could be chosen. Intense discussion and a series of votes followed to whittle down the candidates. The final contest was between two lake sites, Crawford Lake in Ontario, Canada and Sihailongwan Maar Lake, North-East China. Both lakes contain seasonal/annual varves, highly valued by palaeolimnologists as precise records of past environments. In Crawford Lake, which formed in a karstic sinkhole, seasonal changes in lake water chemistry and the ecology of the lake produced alternating layers of dark and pale (more and less organic-rich) calcite sediment. In Sihailongwan Maar Lake, the varves comprise repeated seasonal layers of pale siliciclastic and darker organic-rich sediment. Both lakes have limited catchments and are deep relative to their area, which not only helps burial and preservation but means the lakes are particularly sensitive to atmospheric inputs. Both contain detailed sedimentary records of the unprecedented mid-20th century changes of the Great Acceleration. In the two lakes, the timing of the upturn of fallout radionuclides is practically identical (dated at 1952-1953). Despite the lakes being geographically small and isolated, the geological record they preserve includes globally distributed signals.

The past may broadly remain the key to understanding the present. But that the present is key to the past is now drawn into question

It was a knife-edge contest. Crawford Lake ultimately received the necessary >60% majority of votes from the AWG in July 2023, and so was chosen to host the proposed GSSP. Two further rounds of voting finalised the decision of where and when to place the GSSP in the core using the upturn of the plutonium isotopes 239+240Pu as the primary marker (Fig. 2). The contact between a 0.33-mm-thick pale calcite lamina and overlying dark organic lamina, both assigned a varve age of 1952 CE at 17.0 cm in the selected core, was proposed as the GSSP for the Anthropocene series and Crawfordian stage (Waters et al., 2024). A notional calendar start for this boundary was chosen: 1st November 1952 at 07:15 local time – coincident with detonation of the first thermonuclear device (Ivy Mike) at Enewetak Atoll in the Pacific Ocean – which broadly coincides with the autumn timing of the onset of the distinct rise in plutonium recorded at Crawford Lake.

Figure 2: Plutonium isotopic and spheroidal carbonaceous particle signature in the stratigraphic reference sections. The 239+240Pu plutonium isotopic and spheroidal carbonaceous particle (SCPs) signature in the Crawford Lake, Canada proposed GSSP and complementary reference sections (SABSs) at Beppu Bay, Japan, Sihailongwan Maar Lake, China and the Śnieżka Peatland, Poland, clearly illustrate the Great Acceleration with the marked 239+240Pu isotopic upturn at 1952 providing a dated reference point for the base of the proposed Anthropocene Epoch. Bq kg-1, Becquerel per kilogram; gDM-1, numbers of SCPs per gram of dry mass of sediment. (Figure adapted from Waters et al., 2024. The Anthropocene Epoch and Crawfordian Age: proposals by the Anthropocene Working Group. Executive Summary: doi.org/10.31223/X5VH70)

While Crawford Lake was chosen at the reference point for the Anthropocene boundary, three reference sections that provide complementary expressions of the boundary (Standard Auxiliary Boundary Stratotypes; SABSs) were also proposed, from Beppu Bay, Japan, Sihailongwan Maar Lake, China and the Śnieżka Peatland, Poland (Waters et al., 2024).

The efforts of the AWG over the past 15 years represent an unprecedented exercise in stratigraphy and in the precision of GSSP analysis and correlation, not to mention a unique and ongoing collaboration between Earth science and the humanities.

Uniformitarianism on the rocks

Since its geological analysis began, the Anthropocene has triggered fierce controversy. The AWG submitted their detailed analysis and recommendation to the Subcommission on Quaternary Stratigraphy in October 2023. Ultimately, the proposal to formally define the Anthropocene as an epoch was rejected, in part because seventy years was deemed too brief for a geological epoch, and the strata too insignificant. ICS favoured reinterpreting the Anthropocene as an informal ‘event’ going back 50 millennia and more, to when humans began raising fire and killing mammoths (Gibbard et al., 2022). This is a valid concept, but is a fundamentally different one to the Anthropocene as proposed by Paul Crutzen and analysed by the AWG, where it is the departure from the relatively stable planetary conditions (and resulting stratigraphic signatures) of the Holocene that is key (Head et al., 2023). Furthermore, it requires the unconventional use of ‘event’ for a prolonged diachronous phenomenon and also appropriation of the suffix ‘-cene’, which is typically used to name formal epochs of the Cenozoic. Under a different name, the ‘event’ idea could usefully complement an Anthropocene Epoch, to represent its deep roots in human history.

Excavators at the Inden open coal pit, Germany. The Great Acceleration is characterised by various stratigraphic markers associated with the burning of fossil fuels, including the accelerated production and deposition of spheroidal carbonaceous particles (© Shutterstock)

Crutzen’s Anthropocene is all too real, and will not go away (Hadly & Barnosky, 2024; page 16). Regardless of how we name it, the Anthropocene has already irreversibly set the Earth System on a new course with many consequences, some of which reach into the heart of our science. The past may broadly remain the key to understanding the present. But, its flipside, that the present is key to the past, is now drawn into question. The surrounding controversy recalls those stirred by the concepts of global glaciation in the 19th century and plate tectonics in the 20th century – equally vehemently opposed by many in their time. For geologists who hold uniformitarianism as one of their central tenets of planetary evolution, no wonder this is unsettling.

Dr Simon Turner

Department of Geography, University College London, UK, and Secretary of the Anthropocene Working Group (AWG).

Prof Colin Waters

School of Geography, Geology & The Environment, University of Leicester, UK, and Chair of the Anthropocene Working Group (AWG) 2020–24.

Further reading

• Crutzen, P.J. (2002) Geology of Mankind. Nature 415, 23; https://doi.org/10.1038/415023a
• Gibbard, P. et al. (2022) The Anthropocene as an Event, not an Epoch. J. Quatern. Sci. 37, 395-399; https://doi.org/10.1002/jqs.3416
• Hadly, E. & Barnosky, A. (2024) Love it or hate it, the Anthropocene is here to stay. Geoscientist 34(3), 16-19;
• Head, M.J. et al. (2023) The Anthropocene is a prospective epoch/series, not a geological event.Episodes J. Internat. Geosci. 46(2), 229-238; https://doi.org/10.18814/epiiugs/2022/022025
• Rosol, C. et al. (2023) Evidence and experiment: Curating contexts of Anthropocene geology.The Anthrop. Rev. 10(1), 330-339; https://doi.org/10.1177/20530196231165621
• Steffen, W. et al. (2015) The trajectory of the Anthropocene: The Great Acceleration. The Rev.2(1), 81-98; https://doi.org/10.1177/2053019614564785
• Syvitski, J. et al. (2022) Earth’s sediment cycle during the Anthropocene. Rev. Earth Environ. 3, 179-196; https://doi.org/10.1038/s43017-021-00253-w
• Syvitski, J. et al. (2020) Extraordinary human energy consumption and resultant geological impacts beginning around 1950 CE initiated the proposed Anthropocene Epoch. Commun. Earth Environ. 1, 32; https://doi.org/10.1038/s43247-020-00029-y
• Waters, C.N. et al. (2023) Candidate sites and other reference sections for the Global boundary Stratotype Section and Point of the Anthropocene series.The Anthrop. Rev. 10(1), 3-24; https://doi.org/10.1177/20530196221136422
• Waters, C.N. et al. (2024) The Anthropocene Epoch and Crawfordian Age: proposals by the Anthropocene Working Group. Executive Summary; https://doi.org/10.31223/X5VH70
  • Part 1: Anthropocene Series/Epoch: stratigraphic context and justification of rank: https://doi.org/10.31223/X5MQ3C ;
  • Part 2: Descriptions of the proposed Crawford Lake GSSP and supporting SABSs: https://doi.org/10.31223/X5RD71
• Williams, M. et al. (2022) Planetary-scale change to the biosphere signalled by global species translocations can be used to identify the Anthropocene. Palaeontology 65(4), e12618; https://doi.org/10.1111/pala.12618
• Zalasiewicz, J. et al. (2008) Are we now living in the Anthropocene? GSA Today 18(2), 4-8; https://doi.org/10.1130/GSAT01802A.1
• Zalasiewicz, J. et al. (2017) The Working Group on the Anthropocene: Summary of evidence and interim recommendations. Anthropocene 19, 55-60; https://doi.org/10.1016/j.ancene.2017.09.001
• Zalasiewicz, J. et al. (Eds.) (2019) The Anthropocene as a Geological Time Unit: A Guide to the Scientific Evidence and Current Debate. Cambridge: Cambridge University Press, pp. 361.
• Zalasiewicz, J. et al. (2024) The Anthropocene within the Geological Time Scale: a response to fundamental questions.Episodes J. Internat. Geosci. 47(1), 65-83; https://doi.org/10.18814/epiiugs/2023/023025

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