Nearly two hundred years ago, an event so rare occurred that even the phrase "once in a blue moon" doesn't quite describe it. The thing is, the Sun turned blue in the sky. The effect of the blue, sometimes greenish, Sun was described by numerous observers around the world throughout the summer of 1831, but no one understood what it was. Centuries passed - and finally, scientists were able to literally uncover the true cause of this strange natural phenomenon. A "forgotten" volcano, a catastrophic eruption, and even, indirectly, an abandoned nuclear submarine base were implicated here. Intrigued yet? Then let's read on! More info: PNAS Image credits: EyeEm / Freepik (not the actual photo) The early 19th century was a challenging time for astronomers and farmers around the world. First, in 1816, there was the colossal eruption of Mount Tambora in the Malay Archipelago, causing the so-called "year without a summer." Indeed, throughout Europe and America in 1816, there was virtually no summer, causing widespread crop failures and even famine in some countries. Image credits: Freysteinn G. Jonsson / Unsplash (not the actual photo) Fifteen years later, the situation repeated itself, albeit on a somewhat smaller scale. Cold weather and crop failures came to the Northern Hemisphere, and throughout most of the summer of 1831, astronomers and ordinary people saw a blue Sun, occasionally even shimmering with green or violet hues. All of this was meticulously documented - but this time, scientists were unable to determine the true driver. Image credits: EyeEm / Freepik (not the actual photo) And here's why. The reason is that the Mount Tambora eruption occurred in a densely populated area, close to busy trade routes. Yes, the death toll from the eruption was colossal - it's believed to be over 70,000 people - but on the other hand, scientists were able to clearly record all stages of the eruption and determine its impact on the planet's climate. Image credits: freepik / Freepik (not the actual photo) As for the 1831 case, scientists also suspected a volcanic eruption, but they couldn't find a “suitable” event in the historic records. The prime “suspect” was the small underwater volcano Ferdinandea near Sicily in the Mediterranean, which erupted in July 1831, but the emissions there were too small to cause such severe consequences on several continents. Image credits: wirestock / Freepik (not the actual photo) Well, just in the last couple of years, a team of scientists from the University of St. Andrews, led by Dr. William Hutchinson, appears to have found the true “culprit” of that long-ago event. At least, all modern research methods point almost infallibly to it. Yes, there was a powerful volcanic eruption in the summer of 1831. But it actually occurred thousands of miles from Sicily... Image credits: Daily Galaxy UK / Daily Galaxy Meet Zavaritski volcano on Simushir Island, a small, remote piece of land located in the North Pacific Ocean, between Kamchatka and Japan. It has three volcanic calderas, the youngest of which dates back to modern times, and in its place now lies a lake approximately 70 meters deep. The volcano erupted three times in the last century, most recently in 1957. So why is there absolutely no record of earlier eruptions? It's very simple: firstly, unlike Tambora, Simushir was almost uninhabited in the first half of the 19th century - only small Ainu tribes and the occasional Russian colonist outposts. Consequently, even if there were any witnesses to a massive eruption, they’re unlikely to have recorded it. Image credits: Daily Galaxy UK / Daily Galaxy Secondly, local sources claim that in the second half of the 20th century, Simushir housed a secret military base for Soviet nuclear submarines, which, just like in old James Bond movies, were based right in the volcanic lake. Unsurprisingly, any access to the volcano had been strictly closed to researchers for a long time. In 1994, the base was closed, allowing scientists to study volcanic rocks from Simushir. And so, by comparing ice cores from Greenland and other sites dated to the summer of 1831 with volcanic pumice from the Zavaritski caldera, William Hutchinson's team concluded that a large-scale eruption occurred on Simushir in the summer of 1831, "responsible" for the blue sun and other phenomena. Image credits: Ruslan Aizatulin / Pexels (not the actual photo) Researchers suggest that the "unknown" eruption was one of the largest of the whole 19th century, comparable at least to the 1991 eruption of Mount Pinatubo, which lowered the average annual temperature worldwide by approximately 0.5 degrees Celsius for several years thereafter. Aerosol haze from the volcano's emissions shrouded the Earth and made the Sun appear blue. Commenting on the results of his study, Dr. Hutchinson calls the discovery a true "Eureka moment." Online commenters meanwhile rightly point out how much we still don't know about our planet and how many mysteries lie hidden in its past. However, scientists still uncover these mysteries from time to time. For example, "once under a blue moon… or blue sun."
