Deep within Greenland’s vast ice sheet, scientists have discovered an unusual chemical signal that has sparked years of debate. At the heart of the mystery is a sudden rise in platinum levels found in ice cores (cylinders of ice dug out of ice sheets and glaciers) that date back approximately 12,800 years. This discovery was once considered evidence that Earth may have been hit by a rare meteorite or comet.
New findings suggest a much more realistic explanation. The platinum spikes may have come from an eruption of a volcanic fissure in Iceland rather than an object from space.
Young Dryas and sudden climate change
The timing of this signal is important. It appears to be near the beginning of the Younger Dryas event, a period of dramatic cooling that lasted from approximately 12,870 to 11,700 years ago. During this period, temperatures across the Northern Hemisphere dropped sharply.
This cooling occurred just as the Earth was emerging from the last ice age and beginning to warm. Determining the cause of this sudden reversal could provide valuable insight into how Earth’s climate system behaves under stress.
Researchers now suggest that the cold spell may have been caused by a large volcanic eruption in Germany, or by an as-yet-unidentified volcanic eruption.
Competing theories behind the climate mystery
Ice core records show how extreme the Younger Dryas was. Temperatures in Greenland were more than 15 degrees cooler than today. Across Europe, forests were replaced by tundra and low-latitude rainfall patterns moved south.
The main explanation has long been thought to be a large influx of freshwater from the melting of the North American ice sheets. This surge is thought to have disrupted ocean circulation and cooled the climate. However, another theory claims that a comet or asteroid impact over North America caused this event.
Platinum spikes raise new questions
In 2013, scientists studying ice cores from the Greenland Ice Sheet Project (GISP2) discovered unusually high platinum concentrations. What was particularly puzzling was the ratio of platinum to iridium. Space rocks usually contain high levels of iridium, but this signal did not contain it. The chemical signature also did not match any known meteorites or volcanic materials.
Some researchers suggested that the spikes could be evidence of an unusual asteroid rich in iron. Others suggested it could be related to Germany’s Lake Rahel volcanic eruption, which occurred around the same time and had a unique chemical profile.
To find out, the researchers analyzed 17 samples of volcanic pumice taken from the Lurcher Lake deposit. They created a chemical fingerprint by measuring platinum, iridium, and other trace elements.
The results were conclusive. The pumice sample contained very little platinum, at levels below the detection limit. This ruled out the possibility that the Lurcher eruption was responsible for Greenland’s platinum surge.
Telling stories with different timing and duration
A closer look at the timeline revealed another important clue. The latest ice core dating shows that the platinum spike occurred about 45 years after the Younger Dryas began, too late to cause the initial cooling.
This finding is consistent with previous research. Furthermore, the increase in platinum levels persisted for about 14 years, indicating that there was a sustained process rather than a sudden event like a meteorite or comet impact.
When scientists compared the chemistry of the ice cores to other geological samples, the best match was for volcanic gas condensates (products formed when gases emitted by volcanoes cool from a gaseous to liquid or solid state), particularly those associated with underwater volcanic activity.
Icelandic volcano as a likely source
Iceland’s volcano can cause fissure eruptions that last for years or even decades, coinciding with the 2014 platinum signal. In the period leading up to the Younger Dryas, increased ice sheet melting may have reduced pressure on the Earth’s crust and increased volcanic activity in the region.
Undersea and subglacial eruptions interact with water in ways that can produce unusual chemical signatures. Seawater can remove sulfur compounds while concentrating metals such as platinum in volcanic gases. These gases can travel through the atmosphere and be deposited on ice sheets far away, including in Greenland.
Evidence from the recent Icelandic eruption supports this idea. The Katla eruption in the 8th century led to a 12-year surge in metals such as bismuth and thallium in Greenland’s ice core. The 10th century El Doja eruption left behind a cadmium signal. Although platinum was not measured in these cases, it was shown that Icelandic volcanoes can transport heavy metals over long distances.
Did a volcano cause the Young Dryas?
The platinum spike occurred after cooling began, so it was not the trigger for the Younger Dryas. But other ice core records have revealed massive volcanic sulfate spikes that precisely coincide with the onset of cooling about 12,870 years ago.
The eruption released as much sulfur into the atmosphere as any of the most powerful eruptions in recorded history, whether from Lake Larch or any other volcano. Sulfur in the stratosphere can cool the Earth by reflecting sunlight, which can cause feedback effects such as expanding sea ice, changing winds, and disrupting ocean circulation.
This volcanic activity may have pushed the Earth system back into a cold state, when Earth’s climate was already in a delicate transition between glacial and interglacial periods (periods between cold waves).
What this means for future climate risks
The study focused specifically on the platinum signal and did not evaluate other proposed impact evidence, such as spherules (spherical pieces of molten rock) or black mats (mysterious dark layers in the soil). Still, the simplest explanation based on current evidence points to large volcanic eruptions in the Northern Hemisphere as the primary cause of the Younger Dryas.
Understanding how past events caused rapid climate change is essential to predicting future risks. Large meteorite impacts and large-scale volcanic eruptions are rare in any given year, but they are unavoidable over long timescales. Knowing how the Earth has responded in the past helps scientists prepare for the consequences of future global disruptions.
