Complex sentence: Cerén was evacuated in AD 250 due to the eruption of the Ilopango volcano but was repopulated no earlier than the year 400 and was, at the time of its final evacuation, a tributary to nearby San Andrés.
Split into simpler sentences: Cerén was evacuated in AD 250 due to the eruption of the Ilopango volcano. It was repopulated no earlier than the year 400 and was, at the time of its final evacuation, a tributary to nearby San Andrés.