Medieval moon observations reveal ‘mysterious’ volcanic eruptions

(CNN) – Medieval observations of the Moon are helping researchers study a series of mysterious volcanic eruptions on Earth.

Monks and other scribes of the time gave detailed descriptions of lunar eclipses, when the moon is entirely in the earth’s shadow. At the time, these events were believed to portend disaster.

His writings often referred to a reddish orb orbiting the reckoned moon, as well as more bizarre cases where the refracted moon seemed to disappear completely from the sky.

The Japanese poet Fujiwara no Teika wrote of a dark lunar eclipse “they had never seen in this way before, with the position of the moon’s disk not visible, as if it had disappeared during the eclipse…unprecedented observed on December 2, 1229.”

What historians didn’t know at the time 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.

Guillet believes that medieval manuscripts contain an important source of information about a series of large but poorly understood volcanic eruptions on Earth.

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

Over a five-year period, Guillet and his colleagues searched for descriptions of the Moon in 12th- and 13th-century sources from Europe, the Middle East, and East Asia, which—when combined with data from ice cores and tree rings—allowed a more accurate idea of ​​what scientists believe were some of the largest volcanic eruptions. that 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 Nature, documents were found on 51. In six of these cases, the documents also stated that the moon was exceptionally dark. It was May 1110, January 1172, December 1229, May 1258, November 1258, November 1276.

These dates correspond to five major eruptions identified from traces of volcanic ash found in polar ice cores: in 1108, 1171, 1230, 1257, and 1276 (Volcano 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, constitutes 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 summers on record in the past millennium.”

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

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

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

Little Ice Age

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

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

“A strength of Gillette and co-workers’ study lies in the accuracy with which the authors estimated the timing of volcanic eruptions, noting the year and even in some cases the month of the event,” the colleagues noted. Sim and Zurita did not participate in the investigation.

The study argues that 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 change in the socio-economic system.