We are living in the Meghalayan Age, the most recent officially recognized subdivision of the Holocene Epoch, which itself sits within the Quaternary Period of the Cenozoic Era. The Meghalayan began roughly 4,200 years ago, coinciding with a severe global drought that disrupted civilizations from Egypt to China. It was formally ratified in June 2018, making it one of the newest additions to the geological time scale, and its defining reference point is not a layer of ancient rock but a stalagmite in a cave in northeastern India.
How the Holocene Got Split Into Three Ages
For most of its history as a recognized unit, the Holocene Epoch was treated as a single, undivided block of time starting at the end of the last ice age, about 11,700 years ago. That changed on 14 June 2018, when the Executive Committee of the International Union of Geological Sciences formally ratified a proposal to carve the Holocene into three stages, each anchored by a physical reference point called a Global boundary Stratotype Section and Point, or GSSP.1Journal of Quaternary Science. Subdividing the Holocene Series/Epoch: formalization of stages/ages and subseries/subepochs, and designation of GSSPs and auxiliary stratotypes The proposal was developed by the Subcommission on Quaternary Stratigraphy, approved by the International Commission on Stratigraphy, and then ratified at the top level.2Episodes. Formal ratification of the subdivision of the Holocene Series/Epoch: two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stages/subseries
The three ages, from oldest to youngest, are:
- Greenlandian: The earliest Holocene, beginning about 11,700 years before 2000 CE. Its reference point is in the Greenland NGRIP2 ice core, marking the abrupt warming at the end of the last glacial period.
- Northgrippian: The middle Holocene, beginning about 8,236 years before 2000 CE. Its reference point is in the Greenland NGRIP1 ice core, tied to a well-known cold snap called the 8.2 ka event.
- Meghalayan: The late Holocene, beginning about 4,250 years before 2000 CE. Its reference point is a speleothem (a mineral formation in a cave) from Mawmluh Cave in Meghalaya, northeastern India.
Each boundary corresponds to a distinct, identifiable shift in Earth’s climate system. The idea was not just to impose arbitrary lines but to anchor each division in a real environmental transition that left a measurable mark in the geological record.
Why a Cave in India Defines Our Current Age
The choice of a stalagmite from Mawmluh Cave as the Meghalayan’s reference point raised eyebrows in some quarters, partly because earlier Holocene boundaries were both set in Greenland ice cores. But the decision was deliberate. The Meghalayan boundary corresponds to a global climate disruption known as the 4.2 ka event, a prolonged drought that hit tropical and subtropical regions especially hard. The oxygen isotope record preserved in the Mawmluh Cave speleothem captures a sharp weakening of the Asian summer monsoon at precisely this time.3Quaternary Science Reviews. Exact dating of the Meghalayan lower boundary based on high-latitude tree-ring isotope chronology
The 4.2 ka event was not just a regional hiccup. It has been confirmed as a meaningful climatic divider between the warmer, wetter middle Holocene and the cooler, drier late Holocene across multiple lines of evidence and geographic regions.4Quaternary International. The 4.2 ka BP climatic event and its cultural responses Research in northwestern India, for instance, has linked isotopic enrichment in archaeological bone samples from the Mature Harappan period to a weakened monsoon aligning with this global event, supporting the timing of the Meghalayan onset.5The Holocene. Optically stimulated luminescence dating of Late Quaternary sediments in NW India: Insights into the Meghalayan drought and decline of Indus valley civilization The cultural fallout was real: the drought has been linked to the decline of the Akkadian Empire in Mesopotamia, disruption in the Indus Valley, and upheaval in Egypt’s Old Kingdom. Whether the climate shift alone caused those collapses or just compounded existing pressures is debated, but the environmental signal in the rock and ice is not.
Tree-ring isotope chronologies from higher latitudes have helped pin down the boundary’s exact date to around 2190 BCE.3Quaternary Science Reviews. Exact dating of the Meghalayan lower boundary based on high-latitude tree-ring isotope chronology That kind of precision is unusual for geological boundaries, which are often defined in millions of years. The Holocene’s divisions work on a much finer scale because the record from ice cores, cave deposits, and tree rings preserves annual or near-annual detail.
How Geological Boundaries Get Made
Geological time divisions are not drawn by any single researcher or institution. They go through a layered process involving working groups, subcommissions, the International Commission on Stratigraphy, and finally the executive board of the International Union of Geological Sciences. Working groups identify candidate sections and study the most appropriate physical markers across a range of environments and latitudes. They nominate a specific marker that will serve as the global reference, then the proposal works its way up through multiple rounds of voting and review.6Palaeogeography, Palaeoclimatology, Palaeoecology. Stability and precision in chronostratigraphic definition: The Global Boundary Stratotype Section and Point (GSSP) is the solution – Section: 6. The concept of a GSSP
The system is conservative by design. A new geological time unit has to be supported by a physical reference point that is accessible, well-preserved, and contains a clear signal of the event that defines the boundary. That conservatism is what makes the Anthropocene debate so contentious.
The Anthropocene Proposal and Its Rejection
If you follow science news, you have probably encountered the term “Anthropocene” used to describe our current moment, a time when human activity is the dominant force shaping Earth’s surface, atmosphere, and oceans. The idea has been around in various forms since at least the early 2000s and gained enormous traction in environmental science, the humanities, and public discourse. But as a formal geological epoch, it was rejected.
In 2023, the Anthropocene Working Group submitted a formal proposal to the International Commission on Stratigraphy. It proposed that the Holocene had ended and a new epoch had begun around the mid-twentieth century, anchored by geological signals tied to the Great Acceleration: the sharp rise in industrial output, nuclear weapons testing, fossil fuel combustion, and synthetic chemical production after roughly 1950. The proposed reference site was a sediment core from Crawford Lake in Ontario, Canada, where undisturbed lake-bottom sediments preserve a remarkably clear record of these changes.7Earth’s Future. The Case for the Anthropocene Epoch Is Stronger Than the Case for the Holocene Epoch The Commission rejected the proposal on the grounds that it did not meet the criteria for establishing a new geological epoch.8Journal of Quaternary Science. The Anthropocene: Proposal, rejection, consequences, alternatives, and a lesson
The rejection did not mean the scientific community denies that humans are transforming the planet. It meant that the specific proposal, defining a new epoch starting in the mid-twentieth century, did not clear the procedural and conceptual hurdles the geological community requires. Some critics argued that human impact has been gradual and geographically uneven, stretching back thousands of years, and that pinning the start to roughly 1950 was too narrow. Others felt that an interval of just a few decades was too short to justify a new epoch, a unit that typically spans millions of years.
The Anthropocene as an Event, Not an Epoch
One of the more interesting alternatives to emerge from this debate reframes the Anthropocene not as a formal time division but as an ongoing geological event. This idea comes from multiple research groups who argue that treating the Anthropocene as an event, rather than an epoch, better captures the messy reality of how humans have interacted with the environment over time.9Episodes. A practical solution: The Anthropocene is a geological event, not a formal epoch
Geological events, unlike epochs, do not require a single, globally synchronous start date. They can be spatially and temporally heterogeneous. Deforestation altered landscapes in the Fertile Crescent thousands of years before it did the same in the Amazon. Rice cultivation changed atmospheric methane concentrations long before industrial-era coal burning dwarfed the signal. An event-based framework can accommodate that unevenness without forcing it into a single boundary line.10Journal of Quaternary Science. The Anthropocene as an Event, not an Epoch
This distinction matters more than it might seem. In other fields that have adopted the term, from literature to political science, “the Anthropocene” often functions as a shorthand for an era of human dominance that may stretch back centuries or millennia. The geological community’s insistence on formal definitions and physical reference points can feel rigid from the outside, but it exists to keep the time scale stable and testable rather than shaped by cultural narratives.
What Human Activity Is Leaving in the Rock Record
Regardless of whether the Anthropocene ever becomes an official epoch, the physical evidence that humans are reshaping Earth’s geological record is overwhelming. Manufactured materials like aluminum, plastics, and concrete now show up in modern sediment layers worldwide, alongside global spikes in radioactive fallout from nuclear testing and soot particles from fossil fuel burning. These combined signals make present-day deposits look stratigraphically distinct from anything in the Holocene or earlier epochs.11PubMed. The Anthropocene is functionally and stratigraphically distinct from the Holocene
Some of these markers are strikingly durable. Researchers have documented plastiglomerate, a rock-like material formed when melted plastic bonds with natural sediment during campfire burning. Because the resulting material is denser than loose plastic, it resists being carried away by wind or water and has a higher chance of being buried and preserved in the geological record.12GSA Today. An anthropogenic marker horizon in the future rock record Meanwhile, the explosion of commercial fertilizer use in the twentieth century has left a chemical signature in ice cores, where shifts in nitrogen isotope ratios track the massive increase in soil nitrogen cycling driven by human agriculture.13Geophysical Research Letters. The agricultural history of human‐nitrogen interactions as recorded in ice core δ15N‐NO3−
Even the mineral kingdom has been altered. Since the Industrial Revolution, at least 208 mineral species recognized by the International Mineralogical Association exist principally or exclusively because of human activity. Some are manufactured directly, like synthetic garnets used in lasers and Portland cement compounds. Others form indirectly as weathering products in mine dumps and slag heaps.14American Mineralogist. On the mineralogy of the “Anthropocene Epoch” Many of these materials, including novel metals, tungsten carbide, and boron nitride, along with minerals that were rare before industrialization but are now abundant at the surface like mullite in fired bricks and ettringite in concrete, constitute a genuinely new suite of geological signals in strata forming today.15GeoScienceWorld Books. A Stratigraphical Basis for the Anthropocene
How We Compare to Past Earth-Shaking Events
One way to get a sense of scale is to compare what humans are doing now to past rapid carbon releases in Earth’s history. The go-to comparison is the Paleocene-Eocene Thermal Maximum, or PETM, a warming event roughly 56 million years ago when a massive pulse of carbon entered the atmosphere and ocean, driving temperatures up by several degrees and acidifying the oceans. High-resolution isotope records show that the main carbon release during the PETM happened fast by geological standards.16PubMed Central. Evidence for a rapid release of carbon at the Paleocene-Eocene thermal maximum
What is sobering is that current anthropogenic carbon emissions may more closely resemble a precursor event that preceded the main PETM pulse, a carbon release whose mass and rate more closely match what we are doing now.17PubMed Central. Surface ocean warming and acidification driven by rapid carbon release precedes Paleocene-Eocene Thermal Maximum That comparison is unsettling because the PETM’s main pulse still came after. If the analogy holds, current emissions could be an early chapter in a larger story, though the parallel is imperfect and modern Earth is a very different system from the ice-free world of 56 million years ago.
The Biological Fingerprint We Are Leaving
The geological record is not just about rocks and chemicals. It also tracks life. And by that measure, the current moment is already leaving a distinctive biological signal. Research into the young fossil record, the last few thousand years of preserved remains, shows that human-caused extinctions, species introductions, habitat conversion, and nutrient loading have become the primary factors shaping what populations and communities look like today. Within the last two million years, climate change on its own has rarely been enough to drive major extinction pulses without human pressures compounding it.18PubMed Central. Biology in the Anthropocene: Challenges and insights from young fossil records
The fossil record being assembled right now will look profoundly odd to any future geologist examining it. A sudden worldwide reshuffling of species distributions, with domestic animals and crop plants dominating biomass on every continent, a sharp spike in extinction rates, and the appearance of entirely novel organisms created through selective breeding or genetic engineering. These are the kinds of biological signals that, in the deep past, mark major transitions in Earth history.
Humans as a Geological Force in Their Own Right
Beyond chemistry and biology, there is the sheer physical rearrangement of Earth’s surface. Humans move staggering quantities of rock, soil, and sediment every year through mining, construction, and agriculture. One analysis found that technological mass transport, the dirt and rock we move with machines, exceeds the work of every land-based geomorphic system except rivers.19Earth Surface Processes and Landforms. Hillslopes, rivers, plows, and trucks: mass transport on Earth’s surface by natural and technological processes Gravity, wind, and glaciers all move less material across the landscape than bulldozers and plows do.
This reshaping extends further back than most people assume. The early anthropogenic hypothesis holds that humans began altering atmospheric greenhouse gas concentrations thousands of years ago, through early deforestation and rice cultivation, though the magnitude of that early contribution remains debated. One assessment found that early deforestation could account for only about a quarter of the preindustrial carbon dioxide anomaly, suggesting other factors were also at work.20Reviews of Geophysics. The early anthropogenic hypothesis: Challenges and responses Still, the point stands that human geological agency did not begin with smokestacks. It began with fire, farming, and the axe.
Where the Full Address Stands
If you wanted to write out your current geological address in full, it would read something like: Meghalayan Age, Late Holocene Subepoch, Holocene Epoch, Quaternary Period, Cenozoic Era, Phanerozoic Eon. Every one of those divisions corresponds to a physical marker in the rock or ice somewhere on Earth, verified and ratified through the same institutional process. The Meghalayan is merely the most recently added, and by geological standards the most finely resolved. Whether our geological address ever officially changes to include an Anthropocene epoch remains an open question, but for now, we are Meghalayans, living in an age that began with drought and civilizational upheaval and that, formally at least, continues uninterrupted to the present day.