Geological era of man: when did the Anthropocene begin?

The development of the earth is divided into geological eras.

Geological era of man: when did the Anthropocene begin?

The development of the earth is divided into geological eras. There is a lot of talk right now about the so-called Anthropocene, the human age, because humans have caused drastic changes. Its exact beginning is now to be determined.

The Anthropocene is the geological era of man. But when exactly did it start? In search of a precisely defined starting point, geologists are now pursuing an approach that they take from the earth. They shortlisted twelve sedimentary sequences. They want to use one of these drill cores as a kind of reference to mark the beginning of the human age. A preliminary decision should be made this year, write Colin Waters and Simon Turner in the journal Science. The two researchers are at the head of the group of experts (Anthropocene Working Group; AWG) that is to determine the reference sample.

Geologists divide the earth's history into different eras. Accordingly, humanity is currently living in the Holocene, which began almost 12,000 years ago after the end of the last ice age. However, the AWG experts are of the opinion that the Holocene ended in the mid-20th century. The basis for this is that changes in nature, in the atmosphere, in the soil and in the sediments are largely due to human activities - and leave permanent geological traces.

The term "Anthropocene" was coined in 2000 by the US biologist Eugene Stoermer and the Dutch meteorologist and Nobel Prize winner Paul Crutzen, former director of the Max Planck Institute for Chemistry in Mainz. Since then, the word has been used constantly to highlight the immense - mostly negative - influence of mankind on earth. However, the Anthropocene has not yet been confirmed as an official epoch. Establishing a reference sediment profile is one step in this direction.

It is obvious that mankind has had a massive influence on our planet since the beginning of industrialization at the latest. The atmosphere is warming, sea levels are rising, entire ecosystems have disappeared. Industry and agriculture are shifting cycles of carbon, nitrogen and phosphorus, for example. Substances such as plastic, aluminum and concrete particles find their way into the environment on a global scale. Some animal and plant species are spreading far beyond their original areas, while others are dying out.

This change is also visible and measurable in the sediments, because certain substances from the water or the air are deposited there over time. This allows experts to follow how the earth is changing on the surface. So-called markers include radioactive fallout from nuclear weapons tests, fly ash from industrial production or the ratio of certain nitrogen isotopes. The latter indicates changes in the nitrogen balance, such as over-fertilization due to the start of industrial agriculture, as Reinhold Leinfelder, emeritus at Freie Universität Berlin, explains. He is also a member of the AWG Group.

The twelve drill cores that are now on the shortlist were deliberately taken from very different ecosystems so that the new frontier can also be identified everywhere. There is one from the sediments of the Baltic Sea, from a coral reef off Australia, from the bottom of a Canadian lake, an ice core from Antarctica and a sample from a peat area in Poland. "Taken together, the 12 sites offer a diverse perspective on the geological reality of the Anthropocene," write Waters and Turner.

All samples have in common that they consist of layers of sediment or ice cores that have gradually built up over the past decades. The markers are chosen in such a way that their concentration increased sharply at a certain point in time around the middle of the century - and this change can also be measured at a certain point in the drill cores. One or more such particles or substance concentrations, which appear for the first time or are also increasing rapidly, are intended to define the formal start of the Anthropocene as primary markers.

The search is now on for the drill core that has the ideal prerequisites as a reference sample. "Ideally, the sample site will provide precisely dateable strata with a resolution to pinpoint the onset of the Anthropocene to a specific year," Waters and Turner write. Accordingly, such a reference sample would help to describe the effects of human activities on the planet more precisely - in contrast to the relatively stable Holocene.

"The definition of a geological time period with such reference profiles is standard, so that geologists all over the world have the same understanding of the respective time period and reference profiles can also be examined by others again and again," explains Leinfelder.

However, it may still take some time before the human age is actually included in the geological time scale. The reference proposal still has to be approved by several committees. First by the Subcommission on Quaternary Stratigraphy (SQS), then by the International Commission on Stratigraphy (ICS), and finally by the Executive Committee of the International Union of Geological Sciences (IUGS).

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