Plutonium Spike in Canadian Lake Sediments Marks Dawn of New Epoch in Which Humanity Dominates Planet
Scientists have selected a sinkhole lake in Canada as the site to represent the start of the Anthropocene epoch on Earth, marking the end of stable global environment and the beginning of a new age dominated by human activities. The lake, called Crawford Lake, hosts annual sediments that show clear spikes due to the colossal impact of humanity on the planet since 1950. These include the presence of plutonium from hydrogen bomb tests and particles from fossil fuel burning that have spread worldwide.
If approved by the scientists overseeing the geological timescale, the official declaration of the Anthropocene as a new geological epoch will be made in August 2024. This decision holds not only scientific value but also social and political significance as it testifies to the scale and severity of the planetary transformation processes unleashed by industrialized humanity.
While the climate crisis is the most prominent feature of the Anthropocene, other key impacts include the loss of wildlife, the spread of invasive species, and widespread pollution of the planet with plastics and nitrates. The Anthropocene Working Group, established in 2009, concluded in 2016 that the changes caused by human activities were significant enough to justify the recognition of a new geological time unit.
Several locations worldwide were considered as potential candidate sites, including tropical corals in the US and Australia, a peat bog in Poland, the Antarctic ice sheet, and the debris under the city of Vienna. After multiple rounds of voting, Crawford Lake near Toronto was chosen.
Crawford Lake is unique due to its annual resolution, allowing scientists to observe changes in Earth’s history. The lake’s bottom and surface waters do not mix, providing a clear record in the sediments. The key marker for the Anthropocene selected by the Anthropocene Working Group is plutonium isotopes from hydrogen bomb tests, which were globally spread from 1952 onwards. Other important markers include carbon particles from fossil fuel burning and nitrates from chemical fertilizers.
The 1950s marked the start of the “great acceleration,” an unprecedented increase in industrial, transport, and economic activities that still continue. The increase in plutonium 239 fallout during this period was chosen as the marker for the Anthropocene. The official ratification of the Crawford Lake site and the Anthropocene epoch requires three more votes from geological authorities.
Geologists may face challenges in accepting the concept of the Anthropocene, as they are accustomed to dealing with time periods spanning millions of years and using rocks with fossils as markers. However, the hope lies in the fact that the combined impacts of humanity can be rapidly changed for the better or worse, and that it is not inevitable to slide into continuing environmental poverty.
While some skepticism remains regarding the need for an Anthropocene epoch, many experts view its recognition as a crucial reference point bridging the natural sciences and the humanities. The decision will have implications for understanding and addressing the scale of human influence on the planet.