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Over the past century, the total material wealth of humanity has been enhanced. However, in the twenty-first century, we face scarcity in critical resources, the degradation of ecosystem services, and the erosion of the planet’s capability to absorb our wastes. Equity issues remain stubbornly difficult to solve. This situation is novel in its speed, its global scale and its threat to the resilience of the Earth System. The advent of the Anthropence, the time interval in which human activities now rival global geophysical processes, suggests that we need to fundamentally alter our relationship with the planet we inhabit. Many approaches could be adopted, ranging from geo-engineering solutions that purposefully manipulate parts of the Earth System to becoming active stewards of our own life support system. The Anthropocene is a reminder that the Holocene, during which complex human societies have developed, has been a stable, accommodating environment and is the only state of the Earth System that we know for sure can support contemporary society. The need to achieve effective planetary stewardship is urgent. As we go further into the Anthropocene, we risk driving the Earth System onto a trajectory toward more hostile states from which we cannot easily return.

The term Anthropocene, proposed and increasingly employed to denote the current interval of anthropogenic global environ- mental change, may be discussed on stratigraphic grounds. A case can be made for its consideration as a formal epoch in that, since the start of the Industrial Revolution, Earth has endured changes sufficient to leave a global stratigraphic signature dis- tinct from that of the Holocene or of previous Pleistocene inter- glacial phases, encompassing novel biotic, sedimentary, and geochemical change. These changes, although likely only in their initial phases, are sufficiently distinct and robustly estab- lished for suggestions of a Holocene-Anthropocene bound- ary in the recent historical past to be geologically reasonable. The boundary may be defined either via Global Stratigraphic Section and Point ("golden spike") locations or by adopting a numerical date. Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. This datum, from the perspective of the far future, will most probably approximate a distinctive stratigraphic boundary.

A recently published analysis by Lewis and Maslin (Lewis SL and Maslin MA (2015) Defining the Anthropocene. Nature 519: 171–180) has identified two new potential horizons for the Holocene−Anthropocene boundary: 1610 (associated with European colonization of the Americas), or 1964 (the peak of the excess radiocarbon signal arising from atom bomb tests). We discuss both of these novel suggestions, and consider that there is insufficient stratigraphic basis for the former, whereas placing the latter at the peak of the signal rather than at its inception does not follow normal stratigraphical practice. Wherever the boundary is eventually placed, it should be optimized to reflect stratigraphical evidence with the least possible ambiguity.

Geologist Jan Zalasiewicz takes the reader on a fascinating trip one hundred million years into the future--long after the human race becomes extinct--to explore what will remain of our brief but dramatic sojourn on Earth. He describes how geologists in the far future might piece together the history of the planet, and slowly decipher the history of humanity from the traces we will leave impressed in the rock strata. What story will the rocks tell of us? What kind of fossils will humans leave behind? What will happen to cities, cars, and plastic cups? The trail leads finally to the bones of the inhabitants of petrified cities that have slept deep underground for many millions of years. As thought-provoking as it is engaging, this book simultaneously explains the geological mechanisms that shape our planet, from fossilization to plate tectonics, illuminates the various ingenious ways in which geologists and paleontologist work, and offers a final perspective on humanity and its actions that may prove to be more objective than any other.

The rise of plastics since the mid-20th century, both as a material element of modern life and as a growing environmental pollutant, has been widely described. Their distribution in both the terrestrial and marine realms suggests that they are a key geological indicator of the Anthropocene, as a distinctive stratal component. Most immediately evident in terrestrial deposits, they are clearly becoming widespread in marine sedimentary deposits in both shallow- and deep-water settings. They are abundant and widespread as macroscopic fragments and virtually ubiquitous as microplastic particles; these are dispersed by both physical and biological processes, not least via the food chain and the ‘faecal express’ route from surface to sea floor. Plastics are already widely dispersed in sedimentary deposits, and their amount seems likely to grow several-fold over the next few decades. They will continue to be input into the sedimentary cycle over coming millennia as temporary stores – landfill sites – are eroded. Plastics already enable fine time resolution within Anthropocene deposits via the development of their different types and via the artefacts (‘technofossils’) they are moulded into, and many of these may have long-term preservation potential when buried in strata.

By burning fossil fuels, humans have changed the carbon cycle, loading the atmosphere with extra carbon dioxide (CO2). Before the current Ice Age, high atmospheric CO2 levels generated warm climates. The Ice Age developed as the volcanic supply of CO2 lessened, and rock weathering increased. The CO2 lost from the atmosphere by chemical weathering was transferred to the ocean and trapped in carbonate sediments. Humans now replicate what volcanic activity did in the distant past, our CO2 emissions driving global warming. Earth's present climate should be cool, based on the present configuration of the Earth's orbit and the tilt of its axis, and on the decline in sunspot activity since 1990. Warming will grow further with rising emissions, further raising sea level. If business continues as usual we will end with an Eocene-like ‘greenhouse climate’ and drowned coastal cities.

Global events such as mass extinctions, the onset of Ice Ages, and changes in geochemistry linked with changes in atmospheric chemistry are timeposts in geological strata. In the timeline for Earth history, they allow segmentation of its 4.6 billion year existence into eons, eras, periods, and epochs. As human activity makes its recently initiated yet globally extensive mark that is leading to mass extinctions, changes in atmospheric and marine chemistry, and altering terrestrial features, should a new epoch be declared? Can such an Anthropocene be geologically standardized in strata? Zalasiewicz et al make their case in this article featured in ES&T’s April 1, 2010 print issue recognizing the 40th Anniversary of Earth Day.

We evaluate the boundary of the Anthropocene geological time interval as an epoch, since it is useful to have a consistent temporal definition for this increasingly used unit, whether the presently informal term is eventually formalized or not. Of the three main levels suggested – an ‘early Anthropocene’ level some thousands of years ago; the beginning of the Industrial Revolution at ∼1800 CE (Common Era); and the ‘Great Acceleration’ of the mid-twentieth century – current evidence suggests that the last of these has the most pronounced and globally synchronous signal. A boundary at this time need not have a Global Boundary Stratotype Section and Point (GSSP or ‘golden spike’) but can be defined by a Global Standard Stratigraphic Age (GSSA), i.e. a point in time of the human calendar. We propose an appropriate boundary level here to be the time of the world's first nuclear bomb explosion, on July 16th 1945 at Alamogordo, New Mexico; additional bombs were detonated at the average rate of one every 9.6 days until 1988 with attendant worldwide fallout easily identifiable in the chemostratigraphic record. Hence, Anthropocene deposits would be those that may include the globally distributed primary artificial radionuclide signal, while also being recognized using a wide range of other stratigraphic criteria. This suggestion for the Holocene–Anthropocene boundary may ultimately be superseded, as the Anthropocene is only in its early phases, but it should remain practical and effective for use by at least the current generation of scientists.

Since 2009, the Working Group on the ‘Anthropocene’ (or, commonly, AWG for Anthropocene Working Group), has been critically analysing the case for formalization of this proposed but still informal geological time unit. The study to date has mainly involved establishing the overall nature of the Anthropocene as a potential chronostratigraphic/geochronologic unit, and exploring the stratigraphic proxies, including several that are novel in geology, that might be applied to its characterization and definition. A preliminary summary of evidence and interim recommendations was presented by the Working Group at the 35th International Geological Congress in Cape Town, South Africa, in August 2016, together with results of voting by members of the AWG indicating the current balance of opinion on major questions surrounding the Anthropocene. The majority opinion within the AWG holds the Anthropocene to be stratigraphically real, and recommends formalization at epoch/series rank based on a mid-20th century boundary. Work is proceeding towards a formal proposal based upon selection of an appropriate Global boundary Stratotype Section and Point (GSSP), as well as auxiliary stratotypes. Among the array of proxies that might be used as a primary marker, anthropogenic radionuclides associated with nuclear arms testing are the most promising; potential secondary markers include plastic, carbon isotope patterns and industrial fly ash. All these proxies have excellent global or near-global correlation potential in a wide variety of sedimentary bodies, both marine and non-marine.