European observers noted a completely dark lunar eclipse on May 5, 1110. The Moon completely disappeared from the sky. What really happened? It took more than a thousand years to unravel this mystery.
A major upheaval occurred in Earth’s atmosphere that day: a giant cloud of sulfur-rich particles flowed through the stratosphere, darkening the skies for months or even years, before finally falling to Earth. This veil of dust was the reason why our satellite completely “disappeared” and then reappeared as if nothing had happened. The discovery has been published in the journal Scientific Reports.
A team of researchers from the University of Geneva (Switzerland) has had to review the ice cores of Greenland to identify that, between 1108 and 1113, there was one of the largest sulfate deposition signals of the last millennium. Ice can preserve evidence of volcanism on incredibly long time scales, but determining the precise date of an event that appears in the layers of an ice core remains a tricky business.
“For a long time it was believed that they were the product of the eruption of the Icelandic volcano Hekla in 1104,” they explain, but we know that it really referred to a tropical eruption that occurred in 1108.
How did they find out?
There are several pieces of evidence to support this interpretation. The first is the presence of sulfates in the Greenland ice cores. And not just any ancient deposit, but the largest deposit of the last millennium.
Scientists had assumed that the sulfur deposit had been left behind by a large eruption unleashed in 1104 by Iceland’s Hekla volcano, also called ‘Hell’s Gate’. Given that the thin fringe of ice is among the largest sulfate deposition signals of the last millennium, it sounded plausible. But in the last decade researchers have found that the ice core dates were slightly off, moving the deposit to 1108.
To further explore this idea, the team combined ice core data with historical accounts from around the world. Between 1109 and 1111, there are reports of famines in western Europe related to dramatic changes in the climate, as well as the record of the totally dark lunar eclipse; all this coincides with the story revealed in the ice cores.
“The spectacular atmospheric optical phenomena associated with high-altitude volcanic aerosols have drawn the attention of chroniclers since ancient times,” the team writes.
The volcano responsible for the sulfur cloud that concealed the Moon was Japan’s Mount Asama , which produced a colossal eruption for months in 1108 and whose subsequent eruption in 1783 killed more than 1,4,000 people. It may not be the only factor in this event, the scientists say, but they are confident that it played a key role and that the new dating of the ice cores is correct.
Although the event is well known in the history of astronomy , researchers have never suggested that it could have been caused by the presence of volcanic aerosols in the stratosphere, although that is the most likely cause , the new study suggests.
“We observed that no other evidence of a volcanic dust veil, such as a darkening of the Sun, red twilight glows and / or reddish solar halos, could be found during our investigations during the years 1108–1110 CE,” the researchers write.
Referencia: Guillet, S., Corona, C., Ludlow, F. et al. Climatic and societal impacts of a “forgotten” cluster of volcanic eruptions in 1108-1110 CE. Sci Rep 10, 6715 (2020). https://doi.org/10.1038/s41598-020-63339-3
