Tsunamis can be caused by earthquakes, volcanic eruptions, underwater explosions, landslides, glaciers, and other events. For example, the 2004 Indian Ocean tsunami was one of the deadliest, killing 290,000 people across 14 countries and causing $4-4.5 million in damage to the Aceh region of Indonesia that took 3-5 years to recover from. Tsunamis are destructive waves that form after large displacements of water.