By analyzing layers in the glacier in the Alps, scientists were able to detect variations in medieval lead pollution caused by historic events in England more than 800 years ago.
So what this is about
There was a paper published recently in the Antiquity journal presenting an analysis of the ice core they obtained from the Colle Gnifetti glacier in Switzerland (see the map below). This is a part of Monte Rosa massif, with the highest peaks on the Swiss-Italian border and the highest in the Alps with the exception of Mont Blanc.
The map also shows the glacier route from the Swiss side to the Capanna Gnifetti (or Monte Rosa hut), the highest mountain hut in the Alps. These are high mountains and perhaps you can realize their beauty from this photo I took more than a decade ago from my tour to Fletschhorn. The Monte Rosa hut is on the highest point completely on the left.
Scientists retrieved a 72-meter-long ice core and were able to analyze yearly lead pollution in the European Middle Ages. The physics behind this is that glacier keeps a record of the chemical composition of the air that is trapped in its bubbles. This is somewhat similar to what you have in trees and in their annual growth rings.
In short, they found a physical evidence of the events that took place in England in the period 1170-1220. This all is based on lead pollution caused by atmospheric circulation and winds. The lead was carried by air flows all the way to the Alps and it was deposited there.
In fact, this is an 1170 murder story known from history books, the assassination of Thomas Becket, the Archbishop of Canterbury. The murder was more or less ordered by King Henry II and Becket was beheaded at Canterbury cathedral on 29 December 1170.
Now, there were lots of air pollution from the lead at this time due to lead and silver mining the Peak District and in Cumbria. So scientists were able to observe a huge surge in lead in the air and dust captured in the 12th-century glacier layers. And they also compared the results with the existing tax records of lead and silver production in England from that same period.
In the period before the murder, there is a fall in the lead production that year. But due to the murder, the king was excommunicated by the Pope. So to get himself out of trouble, Henry built and restored many monastic institutions in a short period of time. For this, he needed lots of silver to pay for the works, and lead of course for roofs and pipes, etc.
This increased lead production was clearly detected in the glacier layers. This is not only for the mentioned murder period but also during the wars that were frequent at those times, in this period between 1170 and 1220. Anyway, if you want to read more about the scientific part of the story, the mentioned paper is available here.
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