The Anthropocene

Geologists date epochs from marks left in rock. The proposal here is that human activity has left marks clear enough to count — microplastics in sediment, fly ash from power stations, a spike of carbon-14 from nuclear tests. The debate is not whether the marks exist, but whether they justify a new name.

What is being proposed

The Anthropocene is a proposed geological epoch. Scientists have suggested that humans have become a dominant force shaping the Earth’s environment and climate. It is not yet an officially recognised epoch, but the proposal highlights the extent to which human activities — industrialisation, deforestation, urbanisation — are driving rapid environmental change and species extinction.

Human impacts are significant enough that they are leaving permanent records on Earth’s geology, atmosphere and ecosystems.

The debate

Scientists disagree about whether the Anthropocene should be considered separate from the current Holocene epoch, which began around 11 700 years ago after the last Ice Age.

• Some argue human impacts are significant enough to define a new epoch.
• Others believe these changes, for example in climate, fall within the natural variability of the Holocene.

When would it have started?

The starting point is also debated, with three main proposals.

1610: the carbon dioxide dip

One proposed marker is a dip in carbon dioxide levels around 1610, following the arrival of Europeans in the Americas. The drop is believed to have been caused by the decline of Indigenous populations through European diseases, warfare and slavery, which led to the reforestation of previously farmed land. Those new forests absorbed more CO₂, producing a detectable atmospheric drop. This is sometimes called the “Orbis spike”.

1950: spherical fly ash particles

Another suggested marker is the appearance of spherical fly ash particles in the geological record from around 1950. These were created by burning fossil fuels in coal-fired power plants and have since spread globally, leaving a clear human-made trace in Earth’s sediments. The 1950s also saw the beginning of the “Great Acceleration”, when human impacts such as pollution and greenhouse gas emissions increased dramatically.

1964: carbon-14 markers

The 1964 spike in atmospheric carbon-14, caused by nuclear weapons testing during the Cold War, is a third candidate. Those radioactive isotopes settled into soils and sediments, creating a distinct signal in the geological record.

Evidence of human impact on a planetary scale

Human activity is having a planetary effect that will be detectable in the geological record for millions of years — future geologists could examine Earth’s layers and see clear evidence of our presence, much as we study fossil records to understand ancient life.

1. Chemical pollution accumulating in geological strata. Human-made chemicals such as plastics, pesticides and industrial waste are accumulating in soils and sediments worldwide. Microplastics are a clear example that will be preserved in Earth’s strata far into the future.
2. Mixing of native and non-native species. Global trade and the introduction of invasive species mean species that do not naturally interact now share ecosystems. In future, this mixing will be evident in the fossil record.
3. Modification of terrestrial and marine sedimentary systems. Agriculture, deforestation and urbanisation alter natural sedimentary systems, causing increased soil erosion as topsoil is worn away by wind or water, and changes to river flows and coastal ecosystems as cities and roads block rivers and coastlines, producing unnatural sediment build-up in some areas and erosion in others.
4. Minerals created by human activity. Humans are creating new materials that do not exist naturally — concrete, plastics and metal alloys — which will persist in the geological record for millions of years.

Worked examples