The How, What, Why, When, and Where of Tsunamis

We had a student who traveled to Thailand recently with their family. When they returned home, they came with pictures and stories of how the region was affected by the massive Tsunami that devastated the area in 1994. The information that the student brought back to share with the rest of the class, promoted a long discussion about the topic. So, even though we are not scheduled to begin Earth Science until the Spring, we ended up spending a day on subduction zone earthquakes. I promised the students that I would post the pictures that I showed them during class, so that they could share with their parents their new knowledge.

All drawings are courtesy of The USGS. More information can be found here.

For reference purposes, I have included a map of the affected region and its place on the globe.














The earth is made up of several crustal plates that float on a layer of molten rock. The crustal plates under the oceans are much heavier than the continental plates. Sometimes, the plates are pushing against each other and when this happens, the ocean plate slides under the continental plate to form a subduction zone.












The plates do not always slide smoothly and can get stuck on one another. When this happens, great pressure is slowly built up and the continental crust can get pushed back and upwards.












When the pressure builds up so much that the stuck portions can no longer hold, it releases suddenly. This is an earthquake.













The portion of the continental crust that had been bent upward, springs back into its previous location and pushes all that water out of its way. That pushed water is the Tsunami, which then travels out across the ocean and on to land.