What Caused the Younger Dryas

The Younger Dryas was a cold period which started 12,870 years ago. The last glacial maximum had finished about 20,000 years ago, so there had been about 7,000 years when things had been getting warmer. At 12,870 years ago thing got cooler quickly - in Europe the average temperature dropped 6⁰C in just 3 years! I suspect this would make life difficult for the people in the area. This cooling lasted for 1,170 years.

The causes of this are discussed in THIS ARTICLE, partially based on this JOURNAL ARTICLE, and this MAGAZINE ARTICLE. Possible culprits include:

1. A meteor strike
   
   
2. Drainage from a large glacial lake, disrupting the North Atlantic Drift.
   
   
3. An unknown volcanic eruption. (But not the Laacher See eruption - wrong trace elements and a bit later than the start of the Younger Dryas.)

There is evidence of volcanism at the start of the Younger Dryas. Where it was is still unknown. But the meteor strike is now discounted. We are left with culprits 2 and 3. And they do not rule each other out.

Below I attach a summary of the article which started this post, produced by ChatGPT.

The Earth-logs article argues that the long-debated cause of the Younger Dryas cold interval—an abrupt return to near-glacial conditions about 12,870 years ago—is now effectively resolved. The Younger Dryas interrupted the gradual warming that followed the last Ice Age, with temperatures in parts of the Northern Hemisphere dropping dramatically within just a few years and remaining cold for over a millennium.

Historically, several explanations have competed. One popular idea was that a massive influx of freshwater into the North Atlantic disrupted ocean circulation, particularly the Gulf Stream, reducing heat transport to higher latitudes. Another controversial hypothesis proposed that a comet or asteroid impact triggered the cooling, but this has largely been rejected due to lack of reproducible evidence.

The Earth-logs post highlights newer geochemical and ice-core evidence that points instead to a major volcanic trigger. Ice cores from Greenland show a pronounced sulphate spike at the onset of the Younger Dryas, indicating a very large volcanic eruption. While the well-known Laacher See eruption in Germany occurred around the same time, its scale and chemical signature do not match the observed sulphate anomaly. This implies that a much larger, as yet unidentified eruption injected vast quantities of aerosols into the atmosphere.

Such an eruption would have rapidly reduced incoming solar radiation, causing sharp cooling. Crucially, this initial volcanic cooling could have pushed the climate system past a tipping point, weakening ocean circulation and locking the Northern Hemisphere into a prolonged cold state. In this view, volcanism acted as the trigger, while feedbacks within the ocean–atmosphere system sustained the millennium-long chill.

The article concludes that this combined explanation—a large volcanic event initiating a cascade of climatic feedbacks—best fits the available evidence. It reconciles the abrupt onset seen in ice cores with the extended duration of the Younger Dryas, offering a coherent solution to a long-standing geological puzzle.