On Dec. 26, 2004, a magnitude 9.1 earthquake rocked the bottom of the Indian Ocean off the coast of Indonesia, releasing the energy equivalent of 23,000 Hiroshima-level atomic bombs. If the damage had been contained to the seafloor, it wouldn't have been a big deal. But the powerful quake displaced a tremendous amount of water, sending massive waves of destruction surging toward surrounding coastlines [source: National Geographic].
As tsunami waves measuring no more than a foot (30 centimeters) high swept stealthily across the open ocean, people in surrounding countries went about their daily routines. But soon, strange things began to happen. Some people reported that the ocean was rapidly receding while others heard a roar like a jet engine. As the waves pushed closer to shore they grew taller, reaching as high as 98 feet (30 meters) before crashing onto homes, cars and people in low-lying areas [source: Paris et al.].
Most victims were caught completely off guard because the Indian Ocean region didn't have a tsunami warning system in place. When the waters receded, they left behind 230,000 victims in 15 countries and $14 billion in property damage [source: Kuhne]. It was the deadliest tsunami in recorded history.