How big are tsunamis?

Here is my final version of how big are tsunamis?

The size of a tsunami can be determined by what it is caused by. If the tsunami is caused by an earthquake, the bigger the earthquake is, the bigger the waves. It is the same with landslides, volcanic eruptions and meteorites.

The average size of a tsunami when it is travelling in open water is just centimetres in height. This is because the water is very deep and therefore the wave has a great height underwater. The length of the wave when it is in the open water can reach up to 100 kilometres long. These waves can be separated by as much as an hour. This is what makes a tsunami so powerful.

The size of a tsunami can change dramatically when it reaches the shore. Usually the length of the wave becomes smaller but is still very powerful. The height of the wave is the one that changes the most. The height changes from a few centimetres to more the 30 metres. This happens because when the wave reaches shallow water, the wave height underwater has no where to go so it pushes up making the wave a towering figure.

There is such thing as a mega tsunami which is a huge tsunami. A mega tsunami can be more than 100 metres high and can be very powerful. A mega tsunami can start like any other tsunami, but it usually takes something like a huge earthquake or landslide for it to become much more powerful than normal tsunamis.