We humans have changed the earth more than any organism before us. For this reason, our era is to be included in the geological nomenclature in the future as the “Anthropocene”. A working group of the International Commission on Stratigraphy (ICS) has now selected a global reference point for this: The sediment layers in a small lake in Canada, Crawford Lake, become the Global Stratotype Section and Point (GSSP) – the place on earth where the defining features of the Anthropocene, including the radioactive fallout from the atomic bomb tests of the 1950s and other anthropogenic changes in the environment, are particularly evident. If the other bodies also accept this proposal, the “Anthropocene” could be declared an official epoch in the history of the earth as early as next year.
Officially, we are still living in the geological epoch of the Holocene, which began around 12,000 years ago with the end of the last ice age. As with other geological epochs before it, the beginning of this era is marked by a global and extensive change in environmental conditions or the living environment. In the case of the Holocene, this was the retreat of Ice Age glaciers and the sharp rise in global temperatures. This can be seen from the isotope values and characteristic changes in the fossils and minerals deposited in the geological strata. Other epochal transitions are characterized by large mass extinctions and the changes associated with them, such as the end of the Cretaceous period around 66 million years ago. For thousands of years, little has changed since the beginning of the Holocene around 12,000 years ago, and the earth system has remained relatively stable.
Three prerequisites for the Anthropocene
But with the beginning of modern times and the rapid growth of the world population, this has changed. Mankind is increasingly intervening in material cycles, nature and the climate, and this has long been evident everywhere on planet Earth: in greenhouse gas and pollutant emissions, in the destruction and urban sprawl of landscapes, in the accelerated extinction of species or the ubiquitous remains of plastic and other synthetic materials. As early as 2000, some scientists, including Nobel Prize winner Paul Crutzen, then Director at the Max Planck Institute for Chemistry in Mainz, suggested defining the era shaped by humans as a new geological age – the “Anthropocene”. The International Commission on Stratigraphy (ICS) is responsible for the classification of geological and thus stratigraphic time sequences. It decides if and when a new geological age will be introduced.
In order for this to happen, three requirements must be met: There must be at least one typical feature of the new epoch that is clearly legible and verifiable in geological layers, It must be determined – and based on these features, among other things – when this epoch began, and you need a point of reference – a place where the defining characteristics of the new epoch emerge particularly clearly and representatively. These reference points are called the Global Stratotype Section and Point (GSSP). Because these are marked with gold-colored metal plaques, they are also referred to as “Golden Spike” – Golden Nail. In order for the Anthropocene to become an official geological-stratigraphic epoch, these three questions had to be answered.
Radioactive fallout as marker, Lake Canada as GSSP
In 2009, the International Commission on Stratigraphy set up a working group to examine this. In 2019, after a thorough examination, this Anthropocene Working Group (AWG) decided that there were sufficient indicators for the Anthropocene as a new stratigraphic epoch. However, when this began was initially disputed: Crutzen and others suggested the beginning of the industrial revolution as the starting point. However, the associated geological changes cannot be detected in the same way and at the same time worldwide. The same applies to changes in land use or the detection of synthetic materials. Therefore, it was agreed that the Anthropocene began around 1950. During this period, nuclear weapons testing reached its peak and the plutonium and other radioactive nuclides released were distributed around the world. “In nature, plutonium occurs only in minimal traces. But in the 1950s we see an unprecedented surge of plutonium in drill cores from around the world,” explains Andrew Cundy of the University of Southampton. Also around this time, the end of the Second World War and the subsequent economic recovery led to an acceleration and intensification of anthropogenic interventions in nature and material cycles.
That left the third requirement: a reference point. To this end, the ICS working group has examined twelve candidates on five continents in detail over the past few years. Now the experts have made their choice. The panel proposes Crawford Lake in Canada as the official “Golden Spike” for the Anthropocene. This small lake is located in a nature reserve on the north shore of Lake Ontario. “The lake is very deep for its size at 24 meters,” explains Francine McCarthy of Brocks University in Ontario. Its correspondingly calm deep water allows undisturbed sediment deposition. The annual layers of the sediment are therefore particularly easy to distinguish and thus form a stable geological archive. The environmental changes of the last thousand years can be read from them like “annual rings” – including the strong increase in plutonium and other radioactive isotopes from the atomic bomb tests of the 1950s.
This means that small Crawford Lake is well on the way to becoming the “Golden Spike” for the Anthropocene. The proposal to provide Crawford Lake with the “Golden Spike” for the Anthropocene now has to go through further votes within the stratigraphic community. If he finds appropriate majorities, the International Union of Geological Sciences could ratify the new GSSP in August 2024.
Source: Max Planck Society