Younger Dryas Impact Hypothesis (~12,800 BP)

Hypothesis that fragments of a disintegrating comet struck or airburst over Earth ~12,800 years ago, triggering abrupt cooling.

Specifications & Metrics

type: Catastrophism & Impact Chronologies
timespan: ~12,800 – 11,700 years BP (10,800 – 9,700 BCE; Younger Dryas boundary)
defining boundary: Carbon-rich 'black mat' stratigraphic layer across North America, Europe, and Western Asia
proponents or Body: Richard Firestone, Allen West, James Kennett & Comet Research Group (2007–present)
key evidence: Platinum and iridium anomalies, nanodiamonds (lonsdaleite), magnetic microspherules, meltglass

Proposed in 2007 by Richard Firestone, Allen West, James Kennett, and colleagues, the hypothesis states that fragments of a large, disintegrating comet struck or exploded in airbursts across North America, South America, Europe, and Western Asia around 12,800 years BP.
Across dozens of Younger Dryas Boundary (YDB) sites underlying a dark, organic-rich 'black mat' layer, researchers report peaks in platinum, high-temperature iron/silica microspherules, shock-synthesized nanodiamonds, meltglass (such as at Abu Hureyra in Syria), and soot from continental biomass burning.
The model links the cosmic airbursts and subsequent meltwater pulse into the North Atlantic to the abrupt 1,100-year Younger Dryas return to glacial temperatures, the extinction of Pleistocene megafauna (mammoths, mastodons, saber-toothed cats), and the termination of the Clovis archaeological culture.