Where the "puzzle pieces" come together is called a "fault line." In the United States, many people know of the fault line known as San Andreas Fault. This is where the North American plate and Pacific plate meet.
Even as large as these plates are (see the previous page for the map), they are always moving in a process known as "continental drift." The continents are actually drifting as they "float" on top of the mantle in the Earth's core. However, they are moving very, very slowly. Sometimes, these plates are moving in different directions and the fault lines (where two plates rub up against each other) will move a large distance in a short period of time. Because these plates move more than normal in a short period of time, there is a lot of energy stored up. The sudden release of energy is known as an "earthquake."
Sometimes, these earthquakes happen near or under the ocean. Because earthquakes release such a large amount of energy, the water is displaced. This displacement creates a giant wave called a tsunami, which can be very dangerous when it reaches land.
View more about Earthquake and Tsunami.
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