Youíll know when a tsunami is coming because youíll see a big wave that keeps getting larger and larger like a storm swell. Several minutes after that, the first wave will hit, making the beach flood. Then it will move to the coast. Thatís not all, though. The largest waves are usually the third through eighth. The seismic waves that an earthquake makes travel faster than the tsunami made by the same earthquake. As a tsunami wave travels, it seems to have a lot of different curves, because the water is deeper in some places and shallower in others. As the tsunami nears the coast, it changes. It grows taller and it breaks up into several waves. These waves slow down as they hit the land. How fast a tsunami moves depends on how deep the water is. Meaning if the water is deeper the faster it goes. The height, as it nears the shore, is decided mostly on the appearance of the underwater land surface off the shore. As they decrease in speed, they increase in height. Even though it slows down as it nears the shore, it still has great force underwater. They usually increase in height at slightly curved shores, bays along the coast, or land ridges beneath the sea. As it reaches the coast, it might look like a fast rising or falling tide. Because tsunami waves are so big when they hit the shore, there is nowhere for the water to go but on land, therefore causing terrible flooding. Tsunami waves can be up to 62.14 miles long! They can also be about three feet high in the middle of the ocean. Because of its strong underwater energetic force, the tsunami can rise up to 90 feet, in extreme cases, when they hit the shore! Tsunami waves act like shallow water waves because they are so long. Because it is so long, it can last an hour. In the Pacific Ocean, a tsunami moves 60.96 feet a second, passing through water that is around 1219.2 feet deep.