How they form!
Tsunami's basically come from earthquakes. Undersea landslides (which are created by earthquakes) makes the water maneuver into a stable position making waves not big enough to be a tsunami though, it takes a lot to form a tsunami, that's why they're so rare. An undersea volcano erupts and that give the waves the push it needs to form a tsunami!
Did you know tsunami's are measured in meters, it has to be at least 3 meters to be considered a tsunami. Think of all the families thrown apart and all the things taken from people because of tsunami's. Tsunami's mostly occur in coastal area, and they travel pretty darn far. Think about the Indonesian Tsunami(December 26th, 2004... Indonesia) it traveled all the way to Madagascar. The Tohoku tsunami(March 11th, 2011, Japan). You can prepare for tsunami's by building houses on poles and to have back up generator and to have canned goods and water!