Scottish scientists solve the mystery of the volcano that cooled the world

This cold weather was well-documented worldwide, with the composer Felix Mendelssohn among those who wrote about the catastrophic weather during his summer journey through the Alps in 1831: “Desolate weather, it has rained again all night and all morning, it is as cold as in winter, there is already deep snow on the nearest hills…” 

While scientists knew it was a major event that caused climatic change and societal upheaval, the identity of the volcano responsible remained unknown and fiercely debated, until now. 

New research, led by Dr Will Hutchison from the School of Earth and Environmental Science at the University of St Andrews and published in the journal Proceedings of the National Academy of Sciences, reveals how the team analysed ice core records from the 1831 event and identified a “perfect fingerprint match” of the ash deposits. 

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“Only in recent years have we developed the ability to extract microscopic ash shards from polar ice cores and conduct detailed chemical analyses on them. These shards are incredibly minute, roughly one-tenth the diameter of a human hair,” explained Dr Hutchison. 

Dr Hutchison and his team were able to accurately date and match the ice core deposits to Zavaritskii volcano on the remote, uninhabited island of Simushir, part of the Kuril Islands.  

The islands are a disputed territory between Russia and Japan. Currently controlled by Russia, they operate as a strategic military outpost. During the Cold War, in a plotline reminiscent of a Bond film, the Soviets used Simushir as a secret nuclear submarine base, docking vessels in a flooded volcanic crater. 

“We analysed the chemistry of the ice at a very high temporal resolution. This allowed us to pinpoint the precise timing of the eruption to spring-summer 1831, confirm that it was highly explosive, and then extract the tiny shards of ash. Finding the match took a long time and required extensive collaboration with colleagues from Japan and Russia, who sent us samples collected from these remote volcanoes decades ago. 

“The moment in the lab when we analysed the two ashes together, one from the volcano and one from the ice core, was a genuine eureka moment. I couldn’t believe the numbers were identical. After this, I spent a lot of time delving into the age and size of the eruption in Kuril records to truly convince myself that the match was real.” 

The mystery eruption occurred at Zavaritskii volcano (Simushir Island, Kurils). The explosion generated a 3-km wide caldera revealing spectacular red, black and white layers made up of past eruptive deposits. (Image: Oleg Dirksen) This work highlights the Kuril Islands as a poorly studied yet extremely productive volcanic region. 

The volcano responsible for the 1831 eruption was very remote, yet it had a significant global impact on climate and severe consequences for human populations.  

Identifying the sources of these mystery eruptions is crucial, as it allows scientists to map and monitor the regions on Earth most likely to produce climate-altering volcanic events. 

Dr Hutchison added, “There are so many volcanoes like this, which highlights how difficult it will be to predict when or where the next large-magnitude eruption might occur. 

“As scientists and as a society, we need to consider how to coordinate an international response when the next large eruption, like the one in 1831, happens.”