Describe why tsunamis are so large when they come ashore.

the shallower the sea is the more it grows this is called the shoaling affect it can grow sevarl meters higher

The closer they get to land the bigger tsunamis grow. This is caused by an affect which causes the tsunami grow, due to the water becoming more shallow. The more shallow the bigger the tsunami. The affect can allow tsunamis to grow very tall, including several meters high.