Accounts of The Mysterious "Unknown Eruption" Discovered

The early 1800s were defined by nearly a decade of unusual and pressingly cold weather. The year 1816 in particular earned names such as the 'Year Without Summer' and the 'Year of the Beggar,' with unseasonal frost causing rampant crop destruction and starvation.

Researchers have long suspected that this event was caused by the combination of two massive volcanic eruptions, whose far-reaching clouds of smoke and soot literally blacked out the Sun. However, only one of these volcanic eruptions was ever found on record.

The first, which occurred before the Tambora volcanic eruption of 1815, was quickly coined the "unknown eruption," as it appeared that no living human being had seen it or even knew where it occurred.

Researchers finally found conclusive evidence of the unknown eruption's occurrence in the 1990s thanks to the presence of telltale markers, sulphate aerosols, in Greenland and Antarctic ice cores. This evidence dated the cataclysmic eruption back to before 1810 - setting the stage for Tambora's chilling encore performance six years later.

Now, Caroline Williams and her colleagues from the University of Bristol say they have finally discovered eyewitness accounts of the unknown eruption, placing it at general region and time for the history books.

"I spent months combing through the vast Spanish colonial archive, but it was a fruitless search - clearly the volcano wasn't in Latin America," Williams explained in a recent release. "I then turned to the writings of Colombian scientist Francisco José de Caldas, who served as Director of the Astronomical Observatory of Bogotá between 1805 and 1810. Finding his precise description of the effects of an eruption was a 'Eureka' moment." (Scroll to read on...)

According to writings that began in February of 1809, Caldas had been observing "mysterious" obstructions of the Sun as early as Dec. 1808 that sounded exactly like volcanic smoke clouds. At this time, unusual frost began to impact local crops, much like they would again in 1816.

A second account written by physician José Hipólito Unanue in Lima, Peru helped confirm this discovery, and placed the unknown volcano south of the equator.

More importantly, the two accounts date the eruption to within a fortnight of 4 December 1808.

"There have to be more observations hidden away, for example in ship logs," added Erica Hendy, who helped in the investigation. "Having a date for the eruption will now make it much easier to track these down, and maybe even pinpoint the volcano."

The discovery is detailed in full in the journal Climate of the Past.