Impact or Eruption? The Explosive Debate Buried in Greenland’s Ice
Buried deep within Greenland’s vast ice sheet lies a puzzling chemical signature that has sparked decades of debate. A sharp spike in platinum concentrations, discovered in a Greenland ice core and dated to around 12,800 years ago, was once thought to support the theory of an extraterrestrial impact. But new research suggests a more earthly explanation—volcanic activity in Iceland.
Platinum Spike in Greenland Ice and the Younger Dryas Mystery
Why does this platinum anomaly matter? The spike occurs near the beginning of Earth’s last great cold phase—the Younger Dryas Event (12,870–11,700 years ago). During this period, northern hemisphere temperatures plummeted more than 15°C below today’s levels. Europe reverted to glacial-like conditions, forests gave way to tundra, and global rainfall belts shifted dramatically.
The timing of the platinum surge seemed suspiciously close to this abrupt climate cooling. Could it have been caused by a cosmic strike—or something closer to home?
Comet Impact or Volcanic Eruption? Competing Hypotheses
The traditional explanation for the Younger Dryas centers on a massive pulse of freshwater from melting North American ice sheets. This disrupted the Atlantic circulation system, triggering rapid cooling.
Others proposed a cosmic impact: a comet or asteroid exploding over North America. In 2013, researchers found elevated platinum levels in the Greenland Ice Sheet Project (GISP2) cores—an element commonly associated with meteorites. Yet the chemical ratios raised doubts. Unlike typical space rocks, this spike lacked iridium, making it an odd candidate for an extraterrestrial source.
Meanwhile, volcanologists suggested another culprit: the Laacher See eruption in Germany, a powerful volcanic event with unusual geochemistry that occurred around the same time.
Testing the Laacher See Hypothesis
To investigate, scientists collected and analyzed 17 samples of volcanic pumice from Laacher See deposits. They measured platinum, iridium, and other trace elements, creating a geochemical “fingerprint” of the eruption.
The verdict was clear: Laacher See pumice contained virtually no platinum. Even if some platinum gases escaped during the eruption, the concentrations were far too low to account for the Greenland spike.
Updated ice core chronologies further complicated the cosmic impact theory. The platinum peak actually occurred 45 years after the Younger Dryas began, too late to have triggered the cooling. Even more telling, the anomaly persisted for 14 years, indicating a prolonged event—not the instantaneous signature of a meteorite strike.
Icelandic Volcanoes: A Better Match for the Platinum Signature
When researchers compared the ice chemistry to other geological samples, the closest match came not from meteorites, but from volcanic gas condensates, especially those from submarine eruptions.
This finding aligns with Iceland’s geological history. As ice sheets melted after the last Ice Age, pressure on Earth’s crust lessened, dramatically increasing Icelandic volcanic activity. Large fissure eruptions in Iceland can last for decades—precisely the duration needed to explain the Greenland platinum spike.
Crucially, subglacial or submarine eruptions interact with water in ways that alter volcanic chemistry. Seawater strips away sulfur while concentrating metals like platinum. These platinum-rich gases could have traveled through the atmosphere and been deposited on Greenland’s ice sheet.
Evidence from Historical Icelandic Eruptions
The idea is supported by historical precedents. The Katla eruption in the 8th century produced a 12-year spike of heavy metals in Greenland ice, while the Eldgjá eruption in the 10th century left a cadmium signature. Platinum wasn’t measured in these cases, but they demonstrate Iceland’s ability to inject metal-rich gases into the atmosphere for years at a time.
If Iceland’s volcanoes have done this in recent centuries, why not during the climatic turmoil of 12,800 years ago?
Could Volcanic Eruptions Have Triggered the Younger Dryas?
Because the platinum anomaly postdates the onset of the Younger Dryas, it wasn’t the trigger. Yet, ice cores reveal a massive sulphate spike exactly when the cooling began. This points to a powerful volcanic eruption—perhaps Laacher See or an unknown northern volcano—as the true catalyst.
Sulphur-rich eruptions can dramatically cool the planet by reflecting sunlight back into space. Combined with a climate already teetering between glacial and interglacial states, even one eruption could have tipped Earth into a millennium of cold.
Lessons for the Future: Cosmic Impact or Volcanic Climate Forcing?
The debate over the Younger Dryas raises bigger questions:
How fragile is Earth’s climate system when pushed by sudden shocks?
Are we more at risk from random cosmic strikes or from inevitable volcanic eruptions?
Could a single eruption in Iceland, today, trigger rapid global climate disruption?
While the mystery of Greenland’s platinum spike may be solved by volcanic gases rather than cosmic debris, the larger lesson is sobering. Both meteoritic impacts and volcanic super-eruptions are rare but inevitable. Understanding how past events reshaped climate is vital preparation for the future.
Source: Impact or Eruption? The Explosive Debate Buried in Greenland’s Ice
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