Eclipse Records Pin Dates of 12th and 13th Century Eruptions

On the evening of December 2nd, 1229, Fujiwara no Teika, a Japanese courtier and poet, observed the Moon rising over the hills of Kyoto. The Moon was partially obscured by an eclipse, and as it reached totality, the once bright disk dimmed and appeared to vanish entirely.

Teika recorded in his diary a few days later that the elderly had never witnessed anything like it before. He also added that it was a truly fearful experience and in his 70 years of life, he had never come across anything like it.

Ancient observations by Teika and others of infrequent lunar eclipses in the past have gained significance as scientists have utilized these records to determine the timing of significant volcanic eruptions from almost a millennium ago. This research, published in Nature, has the potential to provide insights into the relationship between volcanism and climate change.

During the March 2020 COVID-19 lockdown, paleoclimatologist Sébastien Guillet from the University of Geneva came across a translated version of Teika’s diary, known as the Meigetsuki. He was extremely excited by this discovery, as it was unexpected and happened purely by chance. For many years, he had been meticulously studying countless medieval manuscripts in search of descriptions of lunar eclipses and the color of the Moon during totality.

If they gave any particulars at all, most of the accounts penned by clerics, monks, crusading soldiers, or urban laymen described a reddish “blood moon” typically seen during a total lunar eclipse on a clear night. A few, however, described eerie dark moons such as the one Teika saw.

During the 12th and 13th centuries, there was a high level of volcanic activity, which is evident from the presence of sulfate layers in ice cores from Greenland and Antarctica. Between 1108 and 1286, there were seven significant volcanic eruptions recorded. However, only one of these eruptions, which occurred in 1257 on the island of Lombok in Indonesia, has been attributed to a specific volcano or location.

Guillet stated that these eruptions are particularly intriguing as they occur during a crucial period: the shift from the warm Medieval Climate Anomaly to the significantly colder Little Ice Age. He wonders if they played a role in this transition and to what degree. There is not a definitive agreement among researchers regarding these inquiries.

To establish a causal relationship, scientists require accurate dating. However, while ice cores provide valuable data, it is difficult to pinpoint specific events to a particular year with certainty. Ice can shift over long periods of time and portions may be lost during the drilling procedure.

“If the date is incorrect, even by a margin of 1 or 2 years, it becomes significantly easier to incorrectly attribute something to a volcano that could simply be a result of natural variability,” stated Guillet. Oppenheimer, a coauthor of the study and a volcanologist at the University of Cambridge, also added that it is possible to mistakenly blame the wrong volcano.

The wonderful thing about eclipses is that we can accurately determine their timing. Furthermore, the shade of the Moon during totality serves as a reliable indicator of recent major volcanic activity.

Volcanic eruptions release sulfur gas and particles into the troposphere, but only the most powerful and explosive ones are able to push them into the stratosphere. In this higher layer of the atmosphere, they are dispersed around the globe and create aerosol veils that block sunlight. These events have the ability to temporarily lower global temperatures, as seen in the 1816 “year without a summer” caused by the Tambora eruption. They also impact eclipses.

During a typical total lunar eclipse, when the Earth passes directly between the Sun and Moon, our atmosphere only permits the longer red light waves to pass through and light up the Moon’s surface. However, if there are a lot of sulfate aerosols in the stratosphere, even these reddish rays are unable to reach the Moon, causing it to appear dark.

Scientists have discovered from notable eruptions, such as Krakatau in 1883 and Pinatubo in 1991, that this phenomenon of an eclipse lasts approximately one year.

Records Revealed

While examining ancient manuscripts from Europe, the Middle East, and East Asia dating back to 1100-1300, Guillet and colleagues discovered numerous records of total lunar eclipses. Interestingly, only Teika’s diary mentioned the color of the Moon, with no other accounts from over 200 Japanese, Chinese, and Korean sources making any mention of it.

But medieval Christians, mostly in Europe, considered a blood-red moon to be a sign of the impending apocalypse, so they were paying particular attention and provided information about the color and brightness of the Moon for 36 eclipses—more than half of those that would have been visible during the period.

Data from past occurrences of total lunar eclipses in 1110, 1172, 1229, 1258, and 1276 coincided with five of the most significant volcanic sulfate signals detected in polar ice cores. Other findings from eruptions that happened near those times revealed a normal red appearance of the moon, leading researchers to suggest that the plumes from these volcanoes likely only reached the lower atmosphere and were possibly located near Greenland, causing an amplified signal.

The team correlated the eclipse information with worldwide aerosol simulations, weather predictions, and summer temperature estimates based on tree rings to determine the timing of these significant volcanic eruptions within a couple of months.

Charlotte Pearson, a geoarchaeologist and dendrochronologist at the University of Arizona, who was not part of the study, stated that it is a sophisticated and fresh method that combines various pieces of evidence.

According to the speaker, volcanic eruptions and eclipses are crucial events that aid in aligning chronologies from various sources, like ice cores and tree rings. “The more we can consolidate all the information into one timeline, the more we can understand the significance of these events for people.”

According to the speaker, historical writers from the Middle Ages documented more than just lunar eclipses, but also extreme weather events such as frosts, failed crops, and famines. These records of eclipses can be used to connect these disturbances to major volcanic eruptions. By studying tree rings for evidence of stunted growth, scientists can confirm that the climate was cooled during years when the Moon appeared black due to an abundance of volcanic dust in the stratosphere.

According to Oppenheimer, the information gathered from these eclipses can offer a unique opportunity to study the dispersion of dust in the atmosphere caused by significant volcanic eruptions during medieval times. This understanding could potentially aid in forecasting the impacts of future volcanic activity.

“Kate Evans (@kate_g_evans), a writer in the field of science.”

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According to Evans (2023), the eclipse records indicate that volcanic eruptions occurred in the 12th and 13th centuries, as reported in Eos, volume 104, published on September 13, 2023. The DOI is 10.1029/2023EO230341.

Text © 2023. The authors. CC BY-NC-ND 3.0

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