(CNN) Medieval observations of the moon are helping modern-day researchers study a mysterious cluster of volcanic eruptions on Earth.
Monks, and other scribes from the time, made detailed descriptions of lunar eclipses, when the moon is completely in the Earth’s shadow. At that time, the events thought to predict calamities.
Their writings often noted a reddish orb surrounding the eclipsed moon, as well as more unusual instances where the eclipsed moon seemed to disappear completely from the sky.
“Old people have never seen it like this time, that the location of the Moon’s disk is not visible, as if it disappeared during the eclipse… This is truly something to fear,” wrote the Japanese poet Fujiwara no Teika, of an unprecedented dark eclipse observed on December 2, 1229.
What the chroniclers could not have known was this: An unusually dark eclipse was associated with the presence of large amounts of volcanic dust in the atmosphere, according to Sébastien Guillet, a senior research associate at the Institute for Environmental Sciences at the University of Geneva.
Guillet believe that medieval manuscripts contain a valuable source of information about a string of large but poorly understood volcanic eruptions on the ground.
“Improving our knowledge of these mysterious eruptions is essential to understanding if and how past volcanism affected not only climate but also society during the Middle Ages,” Guillet said in a news release. .
For five years, Guillet and his colleagues researched 12th- and 13th-century European, Middle Eastern and East Asian sources for lunar descriptions, which — when combined with ice core data and tree ring — allows more precise dating of what scientists think. must be some of the largest volcanic eruptions the world has ever seen.
Volcanic dust
Of the 64 total lunar eclipses that occurred in Europe between 1100 and 1300, the study, published April 5 in the journal Naturefound documentation of 51. In six of these cases, these documents also report that the moon was very 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 polar ice cores — in 1108, 1171, 1230, 1257 and 1276. (Of these, only the location of the eruption in 1257 is known, at the Samalas volcano on the Indonesian island of Lombok.)
“These eruptions are much more powerful than some of the most famous volcanic eruptions in recent history,” Guillet said. “One of these powerful eruptions, the 1257 Samalas eruption, stands as one of the largest volcanic eruptions of the past millennium.”
“The resulting volcanic aerosol blocked sunlight and caused widespread climate disruption. Historical records show that the following summer in Europe… was one of the coldest on record in the last millennium .”
Researchers believe that volcanic eruptions occur three to 20 months before dark eclipses, based on observations of recent eruptions and their effect on lunar eclipses.
“We only know about these eruptions because they left traces in the ice of Antarctica and Greenland,” the study said. co-author Clive Oppenheimer, a professor at the University of Cambridge, in a news release.
“By combining information from ice cores and descriptions from medieval texts, we can now make better estimates of when and where some of the biggest eruptions of this era took place. “
Little Ice Age
Climate scientists typically determine past volcanic eruptions by measuring the amount — and acidity — of volcanic ash in cores drilled from polar ice, or by inferring sudden changes in temperature. in tree ring records.
However, these sources sometimes conflict, as volcanic eruptions disrupt weather patterns in different ways depending on their location, intensity and timing, says Andrea Seim, chair of Forest Growth and Dendroecology at the University of Freiburg’s Institute of Forest Sciences in Germany, and Eduardo Zorita, a senior scientist at the Helmholtz-Zentrum Hereon, a German research center, in a commentary accompanying the study.
“The strength of the study by Guillet and coworkers lies in the precision with which the authors estimated the timing of the volcanic eruptions – determining the year, and even in some cases the month, of the event, ” said the pair. Seim and Zorita were not involved in the research.
The study says 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 Europe’s glaciers, and , according to some historians, lead to changes in the social and economic order.