It has also been decided that the time period will be an “Epoch”, which means that it is a longer than an Age, but not as long as a Period. For example, the Maastrichtian Age is the very last segment of the Late Cretaceous, the final chapter in the history of the non-avian dinosaurs. In this case, the Cretaceous is the Period, and the Late Cretaceous is the Epoch.
Right now, we are in the Quaternary Period, and within this, we are in the Holocene Epoch, which began 11,700 years ago when the glaciers began to retreat and the world warmed. This will now change to the Anthropocene Epoch, which will last tens of millions of years.
There are plenty of markers of human activity, including the fact that plastic has entered the rock cycle, the spike in carbon dioxide in the atmosphere from burning fossil fuels, and the sudden jump in species extinction rates. However, the AWG have settled on the plutonium fallout from the atomic weapons tests that began in earnest in the 50s as the “primary signal”.
There were several options for the start date choice, including around the start of the Industrial Revolution and 7,000 years ago, around the time that advanced agriculture and livestock farming became widespread and methane produced by it began to gradually, but noticeably, warm the climate.
However, by 1950, all human activity had accumulated to the point wherein it was clear beyond any reasonable doubt that we had significantly altered the environment – and what better primary marker to have to underline this than the debris left over from the mushroom clouds of atomic weapons?
In order to make it official, a specific rock unit will need to be found and chosen as containing the “golden spike” – a collection of signals, including the primary signal, which clearly marks the start of the Anthropocene. Only then can an official request be made to the International Union of Geological Sciences, so for now, we’re still officially lounging around in the Holocene.
Plastic entering the rock cycle was another considered primary signal. Rich Carey/Shutterstock