The magnitude and impact of the 431 CE Tierra Blanca Joven eruption of Ilopango, El Salvador

The Tierra Blanca Joven eruption of Ilopango occurred during Maya times but the exact timing and its impact have been controversial. It was thought to be responsible for the anomalously cold decade experienced in the Northern Hemisphere centered at 540 CE, but this date is at odds with archeological evidence that suggests a date near the start of the Early Classic Period (pre-450 CE). Our precise age of 431 ± 2 CE allows us to pinpoint the eruption in proxy records and shows that its impact was apparently limited. It appears to have only had major effects on populations within ∼80 km of the volcano, where the regions were blanketed by decimeters of ash fallout and pyroclastic density currents.