In 1831, a mystery eruption filled the atmosphere with sulfurous gases, causing a 1°C drop in global temperatures and triggering a severe climatic event. Nearly two centuries later, researchers at the University of St Andrews have finally identified its source.
The cooling event nearly 200 years ago reflected sunlight critical for photosynthesis, devastating crops and leading to worldwide famines. For generations, the eruption remained the most recent of the so-called “mystery eruptions”—unidentified volcanic events that altered the climate and, with it, human society, while the volcano responsible remained unknown.
Locating a Devastating Mystery Eruption
The event was anything but subtle for those who lived through it. A written account survives from German composer Felix Mendelssohn, who, traveling through the Alps in the summer of 1831, wrote: “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…”
Despite the severe global cooling that lasted into 1833, scientists remained uncertain about the eruption’s location. Some researchers proposed Ferdinandea in the Strait of Sicily as the likely culprit. Until now, the only solid evidence came from ice cores dating to 1831, which preserved ash samples from the event.
Dr. Will Hutchison, a research fellow at the University of St Andrews School of Earth and Environmental Science, led the new study. Through analysis of ice core records, his team matched the ash deposits to the Zavaritskii volcano on the uninhabited island of Simushir.
Simushir and the Kuril Islands
“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,” Hutchison said. “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.”
Simushir is a remote speck of land in the Kuril Islands, a volcanic archipelago of 56 islands and numerous small islets. Control of the archipelago has long been contested between Russia and Japan; the islands were under Japanese control until they were seized by the Soviet Union after World War II. Today, while the islands are controlled by Russia, they lie only about 800 miles from Hokkaido, Japan.
Simushir is now uninhabited, although during the Cold War, the Soviet Union used the island as the secret location for a base where it moored nuclear submarines in a flooded volcanic crater.
A Challenging Search for a Mystery Eruption
“We analysed the chemistry of the ice at a very high temporal resolution,” Hutchison said. “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.”
Matching those samples was like finding a needle in a haystack. The St Andrews team collaborated with colleagues across Russia and Japan to collect samples from obscure and remote volcanoes.
“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,” Hutchison explained.
Continuing to Monitor Volcanic Climatic Impacts
The team’s work not only solves an almost 200-year-old mystery but also underscores how poorly studied the volcanically active Kuril Islands remain, despite their geological and geopolitical significance. The case of Simushir illustrates how incidents in remote areas can have global climatic consequences, emphasizing the importance of mapping and monitoring volcanic regions that pose potential threats to humanity.
“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,” Hutchison said.
“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.”
The paper “The 1831 CE Mystery Eruption Identified as Zavaritskii Caldera, Simushir Island (Kurils)” appeared on December 30, 2024, in the Proceedings of the National Academy of Sciences.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.