Anthropocene

Topic: Origin and Evolution of the Earth and the Solar System · NCERT: Beyond NCERT

Meaning

Anthropocene ("human-new") is a proposed geological epoch. It would mark the time when human activity became the main force changing the planet [3]. In March 2024, geologists rejected it as an official unit of the time scale. Officially, we still live in the Holocene epoch, Meghalayan age. The word is still widely used informally, and it often comes up in questions on climate change and biodiversity loss [3].

Explanation

Where it would sit on the geological time scale

• Geological time scale: a calendar of the Earth's 4.6 billion years, built from rock layers and the fossils in them.
• The units, from largest to smallest: Eon → Era → Period → Epoch → Age.
• The official chart is the International Chronostratigraphic Chart. The International Commission on Stratigraphy (ICS) keeps it, and the ICS works under the International Union of Geological Sciences (IUGS). Stratigraphy is the study of rock layers and their order in time.
• The present position: Phanerozoic eon → Cenozoic era → Quaternary period → Holocene epoch → Meghalayan age.
• The Quaternary has two epochs. The Pleistocene was the age of the great Ice Ages. The Holocene is the present warm epoch, which began 11,700 years ago.

• The Holocene was split into three ages in June 2018: Greenlandian, then Northgrippian, then Meghalayan [1].

• What the Anthropocene would have changed: it would have been a new epoch after the Holocene, and so a new top layer on the time scale.

How humans leave a mark in the rock record (cause → process → result)

• Cause: after World War II there was a sharp rise in population, economic growth and resource use. This is called the Great Acceleration [3].
• Process: human-made materials settled into fresh layers of mud and sediment all over the world:
• Radioactive fallout (radioactive dust that falls back to Earth) from nuclear bomb tests
• Plastics

• Higher levels of carbon dioxide

• Result: these markers form a layer in the sediment that is different from everything below it. Supporters said this layer could mark the start of a new epoch [3].

The "golden spike" and the proposed site

• GSSP (Global Boundary Stratotype Section and Point), or "golden spike": a single reference point in rock or ice. It shows where a time unit begins.
• A new epoch needs a GSSP. The site proposed for the Anthropocene was Crawford Lake in Halton Region, Ontario, Canada [3].
• The mud at the bottom of the lake builds up in yearly layers, a bit like tree rings [3].
• Plutonium from hydrogen-bomb tests first shows up in the layer for 1952 [3].
• So 1952 at Crawford Lake was put forward as the start of the Anthropocene.

The decision: proposed, then rejected

• Who voted: the Subcommission on Quaternary Stratigraphy (SQS), which is part of the ICS.
• What happened: the SQS rejected the proposal by a wide margin on 5 March 2024 [3]. The IUGS upheld the decision.
• What it means now:
• The official epoch is still the Holocene, and the official age is still the Meghalayan.
• "Anthropocene" stays an informal term. It is still widely used in science and policy [3].

Where it occurs

• World: Crawford Lake, Halton Region, Ontario, Canada. This was the proposed reference site. Its yearly mud layers record plutonium from 1952 [3].
• World, all regions: the proposed markers (radioactive fallout, plastics and higher carbon dioxide) are found in recent sediment layers. They come from the post-war Great Acceleration [3].
• India: Mawmluh Cave, near Sohra (Cherrapunji), East Khasi Hills, Meghalaya. A stalagmite from this cave is the GSSP for the Meghalayan age. That is the age we officially live in, because the Anthropocene was rejected [1][2].
• A stalagmite is a column of limestone that grows up from a cave floor as dripping water leaves minerals behind.
• Mawmluh is the first Indian site to define a global time unit.

Don't confuse with

• Holocene: the official present epoch, which began 11,700 years ago when the last Ice Age ended. The Anthropocene was only a proposed epoch that would have followed it, and it was rejected in 2024.
• Meghalayan age: an official age inside the Holocene, ratified in 2018. It began about 4,200 years ago, and its marker is the Mawmluh Cave stalagmite in Meghalaya [1]. It is a smaller unit than an epoch, and it was approved. The Anthropocene was proposed as an epoch and was turned down.
• Sixth mass extinction: the fast, human-driven loss of species happening today. It describes a biological event. The Anthropocene is a proposed time unit on the geological scale. The two ideas support each other, but they are not the same thing.
• Great Acceleration: the post-World War II rise in population, economic growth and resource use. It is the cause behind the proposed Anthropocene markers. It is not a geological unit [3].

Prelims Hooks

• Trap: "The Anthropocene is the current official epoch of the Earth." This is false. The SQS rejected it on 5 March 2024, and the IUGS upheld the decision [3].
• Current official position: Quaternary period → Holocene epoch → Meghalayan age.
• Proposed GSSP → country: Crawford Lake → Ontario, Canada. Its marker is plutonium in the 1952 mud layer [3].
• Proposed markers: radioactive fallout from bomb tests, plastics and higher carbon dioxide, all linked to the post-war Great Acceleration [3].
• Who decides: the SQS, under the ICS, which works under the IUGS. It is not UNESCO and it is not the IPCC.
• Order of time units: Eon → Era → Period → Epoch → Age. The Anthropocene was proposed at the epoch level.

Mains Points

• Human impact as a geological force (GS-I/GS-III): the formal label was rejected, but the markers are real:
• Plutonium, plastics and carbon dioxide in sediment layers show that humans now leave a lasting signal in the rock record [3].

• The rejection was about formal rules for dividing time, not a denial that this human impact exists.

• Link to biodiversity and climate action (GS-III):

• The Anthropocene idea supports the view that a sixth mass extinction is under way.

• It strengthens the case for global action under the CBD (Convention on Biological Diversity) and the UNFCCC (UN Framework Convention on Climate Change).

• Lessons from past climate shocks (GS-I):

• The present Meghalayan age began with the 4.2 ka event, a drought of about 200 years when the Indian Summer Monsoon weakened [1]. "ka" means thousand years.
• This drought is linked to the Harappan decline. Today's monsoon-dependent farming faces a similar risk as humans warm the planet.

Related concepts

• Mass extinction
• Chicxulub impact
• Lonar crater
• Meghalayan age

Read more

• The geological time scale, impacts, extinctions and the Anthropocene