Constantinople

In 536 CE, Procopius described a remarkable solar eclipse that lasted nearly a year and a half. Procopius reports that in that year the sun did shine, but without its normal brightness, more like a faint moon, as if in a permanent eclipse. He explicitly links this phenomenon to an ominous omen, followed by wars, plagues, and other disasters that led to the deaths of many. He wrote this from Constantinople. According to his account, the "dark sun" would have been visible across large parts of Europe, the Middle East, and parts of Asia. His description is considered today one of the most important contemporary texts on the so-called "volcanic winter" of 535–536, a period of significant cooling and crop failures in the Northern Hemisphere. Modern researchers link the dust or fog curtain he described in the atmosphere to one or more major volcanic eruptions, which cast a veil of ash and dust around the Earth, thus weakening sunlight.

Researchers agree that the cause was volcanic, but aren't entirely sure which volcano or combination of volcanoes was responsible. Often mentioned candidates include a large tropical eruption (for example, Ilopango in El Salvador) and/or a major eruption in Iceland, possibly combined with a second major eruption around 540.

Dromos