Annihilated by hunger, conquered by enemies, wiped out by earthquakes and volcanic eruptions. Much more often, in reality, they have vanished without a clue. We are talking about some great ancient civilizations, which we know existed but we do not know how they disappeared. For example, the Moche in Peru may have been weakened by earthquakes, prolonged droughts and floods caused by El Niño. But there is also an American civilization that disappeared in a mysterious way – the Anasazi.