A tsunami occurs when an earthquake disturbs the seafloor, causing the water above it to form back into a large wave. As the wave moves towards land, it gains more water and becomes bigger and bigger. When it hits the coast, the tsunami behaves like a huge breaking wave, swallowing people and crashing into everything in its path. Before the tsunami, the area had trees and calm water where you could see the landscape, but after, there were no trees, just dirty water and sand everywhere.