If the moon disappeared today and was not visible for weeks, months, or years we would panic. The moon is something that we take as a given in our night sky and while we understand its disappearance for a few seconds during a lunar eclipse, any longer would cause a lot of hysteria. Luckily that is unlikely to happen. In medieval times though it did occur. Now, nearly 1000 years later we finally understand why.
During medieval times most unexplained occurrences were put down to the wrath of the gods. If an eclipse occurred sacrifices were made to appease the anger of the gods. In 1110 when the moon appeared people must have really been wondering what they did that was so wrong that the gods took the moon away.
As we look at some notes that have survived from that time, 1110 was seen as a disastrous year (maybe even strange enough to rival 2020). There was famine, terrible weather and on one particular night the moon disappeared. The moon then stayed away for a long time with no explanation.
Now, many years later, scientists finally understand what happened. To get a clear understanding of what happened back then scientists relied on ice cores from the south and north pole. These cores were able to preserve layers of evidence throughout many centuries and allow scientists to pinpoint exact events. These combined with tree rings and texts from Europe at the time all tell a story.
The story is one of horrible weather conditions that all appear to take place after some significant volcanic eruptions took place. A volcanic eruption has been found in Japan in 1108 that may have caused such a large explosion of ash to enter the atmosphere that it impacted the weather and environment of Europe years later. The eruption of Mount Asma in Japan is believed to have sent large numbers of volcanic particles into the stratosphere and is one possible explanation for the missing moon.
Scientists are unable to say that this eruption was the definite cause but this story makes the most sense. The eruption at the time in 1108 was so strong that it started in August and finished in October. It is believed that the eruption was not only bad enough to cause a long term eclipse two years after the event but that it likely wreaked havoc with the environment for many years as well. In this time there were high rates of famine and extreme weather conditions and the eruption may be to blame for it all.
Prior to this work, it had been thought that an eruption in Iceland in 1104 was to blame but scientists now believe it was the larger and later eruption in Japan that was the cause.
It is incredible to think that a volcanic eruption happening on the other side of the world in 1108 could cause so much upset to occur two years later in Europe. In modern history, we have had a number of volcanic explosions but none of them reached this scale. The last eruption that rated a VEI 7 on the volcanic scale was in 1815, since then we have only had eruptions of VEI 6 and below. The 1815 eruption lowered global temperatures by 5 degrees and 1816 became known as the year without summer. While a disaster some people tie it to the invention of the bicycle as it became impossible to use horses during that period. In 1991 the Philippines had a VEI 6 eruption that killed 850 people. It would have been far more if evacuations had not been made in time.
Clearly the world is not prepared for a VEI 7 eruption or higher to take place. While we can hope that one doesn’t occur in our lifetime, there are many volcanoes that are still active around the world. At any given point one could erupt and change the world as we know it.