Deep within Greenland’s icy sheet, scientists discovered an unusual chemical signal that has long sparked debate among experts. At the center of attention was a sharp spike in platinum levels found in an ice core dated to about 12,800 years ago. This discovery was previously considered possible evidence of a rare meteorite or comet impact on Earth.

New Data and Alternative Explanations

Recent research, however, points to a more terrestrial origin for this phenomenon. It is now believed that the platinum peak may have been caused by a volcanic fissure eruption in Iceland, rather than by a cosmic object.

The timing of this signal coincides with the onset of the Younger Dryas—a period of abrupt cooling that lasted from roughly 12,870 to 11,700 years ago. During this time, temperatures in the Northern Hemisphere dropped significantly, just as the planet was emerging from the last ice age. Understanding the cause of this sudden climate shift is crucial for grasping how Earth’s climate system behaves under stress. Researchers suggest that the cold phase may have been triggered by a major volcanic eruption in Germany or perhaps by an as-yet-unidentified volcano.

Ice Core Data

Records from ice cores reveal just how extreme the Younger Dryas was. In Greenland, temperatures fell by more than 15°C compared to modern values. Across Europe, forests gave way to tundra, and precipitation patterns shifted southward.

For a long time, the main explanation for this cooling was a massive influx of freshwater from melting North American ice sheets, which disrupted ocean circulation and cooled the climate. An alternative theory linked the event to a comet or asteroid impact over North America.

Chemical Analysis and New Conclusions

In 2013, the Greenland Ice Sheet Project (GISP2) detected unusually high concentrations of platinum. The platinum-to-iridium ratio was odd: cosmic bodies typically contain much iridium, but this signal did not. The chemical composition also did not match known meteorites or volcanic materials.

Some experts speculated that the platinum spike could be linked to an unusual iron-rich asteroid, while others suggested it was caused by the eruption of the Laacher See volcano in Germany, which occurred around the same time and has a distinctive chemical profile.

To test this hypothesis, 17 samples of volcanic pumice from Laacher See deposits were analyzed. Measurements showed almost no platinum, ruling out this eruption as the source of the Greenland platinum spike.

A more detailed analysis of the timeline showed that the platinum peak occurred about 45 years after the start of the Younger Dryas—too late to have caused the initial cooling. The elevated platinum levels persisted for about 14 years, indicating a prolonged process rather than a sudden event like a meteorite or comet impact.

Comparison with Other Geological Materials

Comparing the chemistry of ice cores with other geological samples revealed the closest match with condensates from volcanic gases, especially those associated with underwater volcanic activity.

Icelandic volcanoes are capable of fissure eruptions that can last for years or even decades, which aligns with the 14-year platinum signal. In the period preceding the Younger Dryas, accelerated melting of ice sheets reduced pressure on the Earth’s crust, likely promoting increased volcanic activity in the region.

Submarine and subglacial eruptions interact with water in ways that can create unusual chemical signals. Seawater can remove sulfur compounds while concentrating metals like platinum in volcanic gases. These gases can travel through the atmosphere and settle on distant ice sheets, including Greenland.

Confirmation from Later Eruptions

Data from more recent eruptions in Iceland support this idea. The Katla eruption in the 8th century triggered a 12-year spike in metals such as bismuth and thallium in Greenland ice cores. The Eldgjá eruption in the 10th century left a cadmium signal. Although platinum was not measured in these cases, they demonstrate that Icelandic volcanoes can transport heavy metals over great distances.

Since the platinum peak occurred after the onset of cooling, it was not the cause. However, other ice core records show a major volcanic sulfate spike that coincides with the beginning of the cooling around 12,870 years ago.

The Impact of Volcanic Activity on Climate

This eruption—whether Laacher See or another volcano—released enough sulfur into the atmosphere to rival the most powerful eruptions in history. Sulfur in the stratosphere can reflect sunlight and cool the planet, leading to effects such as expanded sea ice, altered wind patterns, and disrupted ocean circulation.

At a time when Earth’s climate was already in a fragile transition between glacial and interglacial conditions, this volcanic activity could have pushed the system back into a colder state.

Implications for Future Research

This study focused exclusively on the platinum signal and did not consider other possible impact evidence, such as spherules or black mats. Nevertheless, based on current data, a major volcanic eruption in the Northern Hemisphere is considered the most likely cause of the Younger Dryas.

Understanding how past events triggered abrupt climate changes is vital for assessing future risks. While large meteorite impacts and powerful volcanic eruptions are rare in any given year, they are inevitable over longer timescales. Studying Earth’s past responses helps us better prepare for the consequences of future global upheavals.