About 1,500 years ago, there were about twenty years of darkness on Earth. The imprint is found in the Greenland ice sheet.
The Sun shone for at most four or five hours a day, but it was permanently obscured, to the point that modern accounts compared its light to that of the Moon.
Beginning in 536 AD, the sky went dark for more than a year. In some parts of Europe and Asia, the sun shone for only about four hours a day, and “the accounts say the sun gave no more light than the moon,” says Dallas Abbott, who studies paleoclimate and extraterrestrial impacts at Columbia University’s Lamont-Doherty Earth Observatory.
The mysterious diminution of the sun caused global cooling, famines, and political unrest. The Chinese reported eclipses that still can’t be explained today. Naturally, “people thought it was the end of the world,” says Abbott.
The scientists presented their theory at a meeting of the American Geophysical Union.
Through research in Antarctica, they discovered that at that time there had been underwater volcanic eruptions that released sediment and microorganisms into the atmosphere, which would be the cause of this giant solar haze. Initially, scientists believed that dust was what was blocking the sunlight, but they couldn’t find scientific evidence to support this.
Underwater volcanic eruptions
By analyzing fossils found in Greenland, researchers were able to confirm the existence of microorganisms and sediments released into the atmosphere by underwater volcanic eruptions, which would have literally “evaporated” large amounts of water and contributed to filling the atmosphere with this material for at least two decades.
In short, a long night whose origins we still do not understand. The answer, however, very often lies right under our feet.
The world did not end then, of course, but this period of sharp decrease in brightness and cooling was the beginning of a longer period of turmoil.
Trees struggled to grow from 536 to 555 AD, which suggests that the solar weakening was widespread and scholars do not know exactly why.
In a poster at the American Geophysical Union meeting, Abbott and his colleague John Barron of the U.S. Geological Survey presented a new interpretation of the event.
Their analysis of a Greenland ice core suggests that undersea eruptions carried sediment and marine microorganisms into the atmosphere, where they helped reduce sunlight.
Volcanic eruptions are known to release sulfur and other particles into the atmosphere that can block sunlight. However, the geological record shows only large eruptions in the 536 and 541 volcanic eruptions, which are not enough to explain the nine-year downward spike in tree growth.
Additionally, it would take a lot of sulfur and ash to darken the sky that much, and some of that material should be visible in rock layers and ice cores. However, Abbott says, “the amount of sulfate deposited was not as great as in other eruptions that experience a similar amount of attenuation.”
