El Salvador eruption in A.D. 536 triggered extreme global cooling

– El Salvador eruption in A.D. 536 triggered extreme global cooling:

Would have filled the skies with ash and dust for more than a year.

El Salvador’s Lake Ilopango – an ancient crater lake boasting 100-meter-tall cliffs – may have been the site of one of the most horrific natural disasters in the world. It may also have caused the extreme climate cooling and crop failures of A.D. 535-536, reports Robert A. Dull of the University of Texas at Austin.

The massive event, the second-largest volcanic eruption in the last 200,000 years, would have instantly killed up to 100,000 people, displaced up to 400,000 more and filled the skies with ash and dust for more than a year. “This event was much bigger than we ever thought,” Dull said.

Such an eruption would explain the extreme global cooling of A.D. 535-536, an 18-month period of cloudy skies, crop failures and famines described in both Roman and Chinese historical accounts. “It’s very well established this event took place,” Dull said. “The question has been the cause.”

Sulfate levels in ice cores from Greenland and Antarctica dated to A.D. 536 indicate that a massive tropical volcanic eruption had ejected ash around the planet. However, the location of such a tropical volcano that could have produced a sufficient volume of ash to block the sun remained unknown.

Over the years, researchers have discovered huge tephra deposits as far away as Nicaragua and Honduras, as well as in offshore deposits.

The wider geographic distribution of deposits indicates that the eruption produced a huge  volume of ash and debris, which Dull now calculates at 84 cubic km (20 cubic miles), more than 64 times as much as the 1980 eruption of Mount St. Helens.

Twenty cubic miles!

“An eruption that big has to leave a big hole in the ground,” Dull said, and the dimensions of Ilopango’s caldera, at 11 kilometers by 17 kilometers, fit the bill. Such an eruption would have been larger than the 1816 eruption of Tambora, which caused the “year without a summer.”

(According to Wikipedia, the Tambora eruption occurred in 1815. It created an ejecta volume of 160 km³ (38 cu mi), much larger than Ilopango. During the following year crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century.)

The most recent eruption at Ilopango took place in 1879-1880, during which a lava dome formed creating the Islas Quemadas in the central part of the lake

http://www.earthmagazine.org/article/aag-eruption-el-salvadors-ilopango-explains-ad-536-cooling

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