(CNN) Medieval observations of the Moon are helping present-day researchers study a mysterious set of volcanic eruptions on Earth.

Monks and other scribes of the era gave detailed descriptions of lunar eclipses, when the moon is completely in the earth’s shadow. At that time, events It was believed to foretell disaster.

Their writings often referred to a reddish orb surrounding the eclipsed moon, as well as more bizarre cases where the eclipsed moon seemed to disappear completely from the sky.

And the Japanese poet Fujiwara no Teika wrote: “The old people did not see it like this time, when the place of the moon disk was not visible, just as if it had disappeared during the eclipse … It was really scary.” , for an unprecedented dark eclipse observed on December 2, 1229.

What historians didn’t know was this: An exceptionally dark eclipse is associated with the presence of a large amount of volcanic dust in the atmosphere, according to Sebastien Gillet, a senior research associate at the Institute of Environmental Sciences at the University of Geneva. .

guillotine Medieval manuscripts are believed to contain an important source of information about a series of large but poorly understood volcanic eruptions On the ground.

“Improving our knowledge of these mysterious eruptions is crucial to understanding whether past volcanism influenced not only climate but also society during the Middle Ages,” Gillette said in a press release.

Over a five-year period, Gillette and his colleagues combed 12th- and 13th-century sources in Europe, the Middle East, and East Asia for descriptions of the moon, which—when combined with ice core and tree ring data—allowed for a more accurate dating of what scientists believe. It must be some of the largest volcanic eruptions the world has ever seen.

Volcanic dust

Of a total of 64 lunar eclipses that occurred in Europe between 1100 and 1300, the study, Published April 5 in the journal Naturefound documentation for 51. In six of these cases, these documents also stated that the moon was exceptionally dark – in May 1110, January 1172, December 1229, May 1258, November 1258 and November 1276.

These dates correspond to five major volcanic eruptions identified from traces of volcanic ash found in the polar ice cores – in 1108, 1171, 1230, 1257 and 1276 (on the Indonesian island of Lombok.)

“These volcanic eruptions were much more powerful than some of the most famous volcanic eruptions in recent history,” Gillette said. “One such powerful eruption, the 1257 eruption of Samalas Volcano, stands as one of the largest volcanic eruptions of the past millennium.”

“The resulting volcanic aerosols blocked sunlight and caused widespread climatic disturbance. Historical records show that the following summer in Europe…was one of the coldest on record over the past millennium.”

Researchers believe that the volcanic eruptions occurred between three and 20 months before the dark eclipses, based on observations of recent eruptions and their impact on lunar eclipses.

“We only learned about these eruptions because they left traces in the ice of Antarctica and Greenland,” the study said. Co-author Clive Oppenheimer, professor at the University of Cambridge, said in a press release.

“By piecing together information from ice samples and descriptions from medieval texts, we can now make better estimates about when and where some of the largest volcanic eruptions of this period occurred.”

Little Ice Age

Climate scientists usually determine past volcanic eruptions by measuring the amount — and the acidity — of volcanic ash in excavated cores of polar ice, or by inferring sudden temperature changes in tree ring records.

However, these sources sometimes conflict, because volcanic eruptions disrupt weather patterns in different ways depending on their location, intensity and timing, said Andrea Sim, chair of the department of forest growth and tree ecology at the Institute of Forest Sciences at the University of Freiburg in Germany, and Eduardo Zurita. , a senior scientist at Helmholtz-Zentrum Hereon, a German research center, in a commentary accompanying the study.

“A strength of Guillet and colleagues’ study lies in the accuracy with which the authors estimated the timing of volcanic eruptions — pinpointing the year, and even in some cases the month of the event,” the pair noted. Sim and Zurita did not participate in the research.

The study said the new research will help shed light on the onset of the Little Ice Age, a period of cold weather between 1280 and 1340 that disrupted crops, saw the advance of European glaciers, and, according to some historians, It led to a transformation of the social and economic system.