"Mystery Volcano" That Caused Mini Ice Age Identified

After 200 years, the unknown volcano that erupted so explosively in 1831 that it cooled Earth’s climate, has been identified.

The eruption was one of the most powerful of the 19th century, spewing so much sulfur dioxide into the stratosphere that annual average temperatures in the Northern Hemisphere dropped by about one 1 degree Celsius (1.8 degrees Fahrenheit). The event took place during the last gasp of the Little Ice Age, one of the coldest periods on Earth in the past 10,000 years.

While the year of this historic eruption was known, the volcano’s location was not. Researchers recently solved that puzzle by sampling ice cores in Greenland, peering back in time through the cores’ layers to examine sulfur isotopes, grains of ash and tiny volcanic glass shards deposited between 1831 and 1834.

Using geochemistry, radioactive dating and computer modeling to map particles’ trajectories, the scientists linked the 1831 eruption to an island volcano in the northwest Pacific Ocean, they reported last 31 December in the journal Proceedings of the National Academy of Sciences.

According to the analysis, the mystery volcano was Zavaritskii (also spelled Zavaritsky) on Simushir Island, part of the Kuril Islands archipelago, an area disputed by Russia and Japan. Before the scientists’ findings, Zavaritskii’s last known eruption was in 800 BC.

"For many of Earth’s volcanoes, particularly those in remote areas, we have a very poor understanding of their eruptive history," said lead study author Dr. William Hutchison, a principal research fellow in the School of Earth and Environmental Sciences at the University of St. Andrews in the United Kingdom.

"Zavaritskii is located on an extremely remote island between Japan and Russia. No one lives there and historical records are limited to a handful of diaries from ships that passed these islands every few years," Hutchison told CNN in an email.

With little information available about Zavaritskii’s activity during the 19th century, no one previously suspected that it could be a candidate for the 1831 eruption. Instead, researchers considered volcanoes that were closer to the equator, such as the Babuyan Claro volcano in the Philippines, according to the study.

"This eruption had global climatic impacts but was wrongly attributed to a tropical volcano for a long time period," said Dr. Stefan Brönnimann, unit leader in climatology at the University of Bern in Switzerland. "The research now shows that the eruption took place on the Kurils, not in the tropics," said Brönnimann, who was not involved in the study.