Echoes of The Past 
A YEAR OF DARKNESS, DESPAIR, AND NEAR EXTINCTION.
In 536 AD, a mysterious fog darkened the skies across Europe, the Middle East, and parts of Asia for 18 months. Temperatures dropped, crops failed, and famine spread. Modern scientists believe the cause was a massive volcanic eruption—possibly in Iceland—triggering a global climate catastrophe. This was followed by plague and war, plunging the world into what some historians call the worst year to be alive.
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Ignaramis you silly puts no human but globalegasses volcano and such study your history
This was the period when the barbarian heathen Anglo-Saxons conquered Britain, forcing the Romanized British Celts into Wales, Scotland,Cornwall etc. And there are so many volcanoes threatening to go off today, all this could happen again. 🧟
I've read that the cause of this same disaster was a meteor that entered atmosphere over Brazil with large parts hitting between there and Britain. This is thought by some to have caused a mass exodus of sorts into France and the Low Countries that lasted approximately 10 years before they returned.
This is not original research. It copies that produced in a BBC TV series Secrets of the Dead aired in the 2000s.
The offending volcano originated in Indonesia and believed to have been a prot Krakztoa.