The Younger Dryas Impact: The Comet That Reset Civilization

Around 12,800 years ago, something catastrophic happened to Earth. In geological terms, it happened overnight. Temperatures in the Northern Hemisphere plunged by as much as 8 degrees Celsius in a matter of decades — possibly in a single year. The warming trend that had been melting the great ice sheets for thousands of years reversed violently. Megafauna that had survived millions of years of climate oscillations suddenly vanished: mammoths, mastodons, saber-toothed cats, giant ground sloths, short-faced bears, American horses, American camels — gone. In North America, the Clovis culture, the most widespread and successful human adaptation on the continent, disappeared from the archaeological record.

This period is called the Younger Dryas, named after a cold-weather wildflower (Dryas octopetala) whose pollen suddenly reappears in European lake sediments at this boundary. It lasted approximately 1,200 years, ending as abruptly as it began around 11,600 years ago, when temperatures spiked upward again by 10 degrees Celsius in perhaps a single decade.

For decades, the standard explanation was that the Younger Dryas was triggered by a massive influx of freshwater into the North Atlantic — meltwater from Lake Agassiz, the enormous glacial lake that covered much of central North America, bursting through an ice dam and shutting down the Atlantic thermohaline circulation. It was a tidy, contained explanation.

Then, in 2007, a team led by Richard Firestone of Lawrence Berkeley National Laboratory, James Kennett of UC Santa Barbara, and Allen West published a paper in the Proceedings of the National Academy of Sciences that proposed something far more dramatic: the Younger Dryas was triggered by the impact or airburst of a large comet or asteroid fragments striking the Earth.

The Evidence Trail

The Younger Dryas impact hypothesis (YDIH) rests on a growing body of physical evidence found at a distinctive boundary layer dating to approximately 12,800 years before present. This boundary layer has now been identified at more than 50 sites across five continents. Here is what it contains.

Nanodiamonds. Tiny diamonds that form only under conditions of extreme pressure and temperature — precisely the conditions created by cosmic impact or airburst. In 2009, Douglas Kennett and colleagues reported nanodiamonds, including lonsdaleite (hexagonal diamond, previously found only in meteorites and impact craters), in sediments from multiple Younger Dryas boundary sites across North America and also in lake bed cores from Lake Cuitzeo in Mexico. Lonsdaleite requires pressures above 70 gigapascals to form — conditions achievable only through extraterrestrial impact.

Magnetic and glassy microspherules. Tiny iron-rich spheres and droplets of melted glass that form when material is heated above 1,700 degrees Celsius and rapidly cooled. These are found in the Younger Dryas boundary layer across North America, Europe, and the Middle East, and are compositionally distinct from volcanic or industrial spherules.

Platinum anomaly. In 2013, Michail Petaev and colleagues at Harvard reported a hundredfold spike in platinum concentration in the GISP2 ice core from Greenland, dated precisely to approximately 12,890 years before present. Platinum is rare in Earth’s crust but common in certain types of meteorites and comets. In 2017, Christopher Moore and colleagues extended this finding, documenting platinum anomalies at eleven continental sites dated to the Younger Dryas boundary. The geographic spread is now global — sites in North America, South America, Europe, the Middle East, and South Africa all show elevated platinum at the same stratigraphic level.

Meltglass. High-temperature glass formed by temperatures exceeding 1,700 degrees Celsius, found at multiple Younger Dryas boundary sites. In 2012, a study documented meltglass at Abu Hureyra, a site in modern Syria, with formation temperatures estimated at 1,720 to 2,200 degrees Celsius — far higher than any known human technology of the period could achieve, and consistent with cosmic airburst.

Shocked quartz. In 2024, James Kennett and colleagues reported the presence of shock-fractured quartz at sites in New Jersey, Maryland, and South Carolina, dating to the Younger Dryas boundary. Shocked quartz forms only under the extreme pressures of cosmic impact — typically above 2 gigapascals. The paper, published in ScienceOpen’s Airbursts and Cratering Impacts, concluded that the pressures and temperatures were consistent with “touchdown” airbursts rather than direct crater-forming impacts.

Biomass burning. Continental-scale charcoal layers at the Younger Dryas boundary indicate massive, simultaneous wildfires. In 2018, a study published in Scientific Reports documented the impact signature in sediments from Patagonia, southern Chile, including evidence of biomass burning, providing the first South American evidence for the YDIH.

The Impact Scenario

The current model does not envision a single asteroid striking the Earth and leaving one giant crater. Instead, the hypothesis proposes that a large comet — possibly 100 kilometers in diameter — fragmented as it entered the inner solar system, and multiple fragments struck Earth’s atmosphere in a concentrated bombardment. Some fragments would have detonated as airbursts (like a vastly amplified version of the 2013 Chelyabinsk event, which injured 1,500 people and damaged 7,200 buildings from a mere 20-meter-wide object). Others may have struck the Laurentide Ice Sheet, which covered much of North America in ice up to 3 kilometers thick.

An impact on the ice sheet would explain two things simultaneously: the lack of a visible crater (the ice absorbed the impact and subsequently melted) and the catastrophic freshwater flooding that disrupted the Atlantic circulation. The comet did not just trigger the Younger Dryas cooling through atmospheric effects — it also released enough meltwater to shut down the ocean conveyor belt, creating a double mechanism of devastation.

The Taurid meteor stream, through which Earth passes twice a year (producing the Taurid meteor showers in June and November), has been proposed as the source. Astronomer William Napier and others have argued that the Taurid stream contains the debris of a giant comet that entered the inner solar system approximately 20,000 to 30,000 years ago and has been progressively fragmenting. Comet Encke, with a nucleus diameter of about 4.8 kilometers, is believed to be the largest surviving fragment.

The Hiawatha Crater: A Dead End

In 2018, a 31-kilometer-wide impact crater was discovered beneath the Hiawatha Glacier in northwestern Greenland, generating enormous excitement among YDIH proponents. The crater had a rim-to-floor depth of 320 meters and a central uplift up to 50 meters high — clearly the signature of a major impact. If it dated to 12,800 years ago, it would provide the “smoking gun” crater that critics demanded.

However, in 2022, Gavin Kenny and colleagues dated the crater using argon-argon analysis of impact-melted sand and uranium-lead analysis of shocked zircon crystals. The result: approximately 58 million years old — Late Paleocene, formed when Greenland was covered in temperate forest, not ice. The Hiawatha crater is real and impressive, but it has nothing to do with the Younger Dryas.

This is science working as it should: a hypothesis generates predictions, evidence is tested, and conclusions adjust. The absence of a confirmed Younger Dryas crater remains the biggest challenge for the impact hypothesis. But proponents argue that airburst events and impacts on ice sheets would not necessarily leave preserved craters, and that the physical and chemical evidence at more than 50 boundary sites constitutes its own form of proof.

The Scale of Destruction

To understand what this means for the question of lost civilizations, consider the scale. If the Younger Dryas was indeed triggered by a cosmic impact or series of airbursts, the effects would have been civilization-ending by any measure. Massive wildfires consuming millions of square kilometers. Tsunamis generated by oceanic impacts or ice-sheet collapse. A nuclear-winter-like pall of dust and smoke blocking sunlight. A sudden return to Ice Age temperatures lasting over a millennium.

Every coastal settlement on Earth would have been destroyed — not once, but repeatedly, as massive meltwater pulses raised sea levels by as much as 120 meters total between the Last Glacial Maximum and the present. Any civilization concentrated along coastlines (as virtually all civilizations are) would have been erased from the map. And if that civilization had not yet developed writing — or if its records were kept on perishable materials — nothing would remain except the stone structures too massive to wash away and the myths too deeply embedded to forget.

The Scientific Debate

The Younger Dryas impact hypothesis remains one of the most contested ideas in Earth science. James Lawrence Powell, in a 2022 review published in Science & Society, compiled 771 peer-reviewed papers on the topic housed on ScienceOpen and found that approximately 73 percent support at least some aspect of the YDIH evidence. A 2023 paper by Holliday and colleagues in Earth-Science Reviews mounted a comprehensive critique, arguing that the evidence involves “flawed methodologies, inappropriate assumptions, and questionable conclusions.” The YDIH team responded with a detailed rebuttal.

What is not in dispute is that the Younger Dryas happened — a catastrophic, rapid climate shift that devastated ecosystems across the planet, drove dozens of megafauna species to extinction, and obliterated the Clovis culture. The question is mechanism: gradual meltwater routing, or cosmic bombardment? The evidence continues to accumulate on both sides.

For Graham Hancock, the Younger Dryas is the key to everything. It provides the mechanism for the destruction of his hypothesized lost civilization. It explains why we find no intact cities from the Ice Age — they were destroyed by impact, fire, flood, and 1,200 years of freezing darkness. It explains why knowledge survived only in fragments, encoded in myth and stone. And it explains why the first recognized civilizations appear, seemingly from nowhere, almost immediately after the Younger Dryas ends around 9600 BCE — the same date as the founding of Gobekli Tepe.

The comet that ended the Ice Age may also have ended a world we never knew existed. The evidence is written in nanodiamonds and platinum, in the bones of vanished giants and the ashes of ancient fires, waiting at a depth of 12,800 years beneath our feet.

If a civilization existed before the Younger Dryas, and if a comet erased it from the surface of the Earth — how would we ever know, except through exactly the kind of fragmentary, anomalous evidence that mainstream archaeology keeps dismissing?