Mystery 7th-Century Volcanoes That Chilled the Earth Finally Traced
In the 7th century, the world got suddenly, eerily cold. Tree rings stunted. Suns dimmed across the Mediterranean. Empires trembled.
Now, scientists have pinpointed the culprit not as one volcano, but several—including a surprising “moderate” eruption from Oregon that hurled ash all the way to Greenland.
By drilling into the Greenland ice sheet, researchers from the University of St Andrews and their international partners have dated four major 7th‑century eruptions with remarkable precision. Their study, published in Quaternary Science Reviews, rewrites what we thought we knew about ancient climate shockwaves.
The largest of these events, in 626 CE and 682 CE, left unmistakable fingerprints in the ice. The 626 eruption—which triggered severe Northern Hemisphere cooling and coincided with the collapse of the Eastern Turkic Empire—was not a tropical monster but an extratropical blast, likely from a still‑unidentified volcano in the North Pacific arc (the chain including Alaska’s Aleutians and Russia’s Kamchatka). Chemical signatures in the ice show its sulfur plume punched into the stratosphere, spreading a cooling veil for years.
The 682 event was genuinely tropical—one of the seven largest sulfur injections of the last 2,500 years, on par with Indonesia’s 1815 Tambora eruption. But its exact source remains a ghost, despite past speculation linking it to Papua New Guinea’s Rabaul volcano.
Most unexpectedly, the team solved a smaller puzzle: a thin layer of ash in Greenland ice dated to 686 CE. They matched it to the Newberry Pumice eruption from Oregon’s Newberry Volcano—only a VEI 4 event (the scale is logarithmic, with 4 considered “moderate”). Until now, no one thought such a modest eruption could send ash 5,000 kilometres across a continent and an ocean. But the Greenland core contained dozens of microscopic glass shards, proving it did.
The sulfur from Newberry, however, never reached the upper stratosphere. Isotope analysis reveals its plume stayed mostly in the lower atmosphere, meaning its climate effect was local, not global. Yet the discovery carries a modern warning: even moderate volcanoes, given favourable winds, can paralyse airspace and disrupt economies across continents.
Finally, the team debunked a long‑held assumption about a 698 CE sulfate spike previously thought to be tropical. The ice shows it came from a high‑latitude Northern Hemisphere eruption—a reminder that matching Antarctic and Greenland peaks does not always signal an equatorial source.
The work turns ice into a time machine. While the 626 and 682 eruptions remain officially “unidentified,” their chemical signatures now rule out many prime suspects, sharpening the search. And the humble Newberry Pumice—once just a regional footnote—has become a trans‑Atlantic marker, tying together ice cores, lake sediments, and ancient tree rings.
For climate modellers, the message is clear: not all planet‑cooling eruptions come from the tropics. Sometimes, the chill begins closer to home.