By observing the night sky, medieval monks unwittingly recorded some of history’s largest volcanic eruptions.
By observing the night sky, medieval monks unwittingly recorded some of history’s largest volcanic eruptions. An international team of researchers, led by the University of Geneva (UNIGE), drew on readings of 12th and 13th century European and Middle Eastern chronicles, along with ice core and tree ring data, to accurately date some of the biggest volcanic eruptions the world has ever seen. Their results, reported in the journal Nature, uncover new information about one of the most volcanically active periods in Earth’s history, which some think helped to trigger the Little Ice Age, a long interval of cooling that saw the advance of European glaciers.
It took the researchers almost five years to examine hundreds of annals and chronicles from across Europe and the Middle East, in search of references to total lunar eclipses and their colouration. Total lunar eclipses occur when the moon passes into the Earth’s shadow. Typically, the moon remains visible as a reddish orb because it is still bathed in sunlight bent round the Earth by its atmosphere. But after a very large volcanic eruption, there can be so much dust in the stratosphere – the middle part of the atmosphere starting roughly where commercial aircraft fly – that the eclipsed moon almost disappears.
Medieval chroniclers recorded and described all kinds of historical events, including the deeds of kings and popes, important battles, and natural disasters and famines. Just as noteworthy were the celestial phenomena that might foretell such calamities. Mindful of the Book of Revelation, a vision of the end times that speaks of a blood-red moon, the monks were especially careful to take note of the moon’s coloration. Of the 64 total lunar eclipses that occurred in Europe between 1100 and 1300, the chroniclers had faithfully documented 51. In five of these cases, they also reported that the moon was exceptionally dark.
Read more at Université de Genève
Image: Illumination from the late 14th or early 15th century, which portrays two individuals observing a lunar eclipse. It features the words «La lune avant est eclipsee», «The moon is eclipsed» in english. (© Source gallica.bnf.fr / BnF via Université de Genève)
