An 8.0 magnitude earthquake on Thursday sent a tsunami toward the Solomon Islands, killing at least nine people. The death toll is expected to rise. Tsunamis can form following various events, including earthquakes, underwater landslides and volcanic eruptions. Such events cause major displacements of water at sea, which in turn send surges of waves toward land. As tsunami waves approach coastal areas, the top of the waves travel faster than the bottom, causing the water level to rise.