The deathly gloom was probably the result of a massive volcanic eruption, perhaps in North America, perhaps in Iceland, perhaps in the mid-Pacific, which released gargantuan clouds of ash and dust. And it was followed in 539 or 540 by another vast volcanic eruption, probably at Ilopango in modern El Salvador.40 Together these natural explosions spewed out several dozen cubic miles of rock and pumped more than one million tons of sulfur and
