On December 26, 2004, a major earthquake occurred off the west coast of Sumatra. Because it happened in the Indian
Ocean, the energy released caused waves to form. When these waves reached land, they caused a lot of damage and loss of life. Could this happen in New York? Can people recognize waves formed by an earthquake in time to protect themselves?
Most earthquakes happen because the solid crust of the earth floats on the earth’s liquid core. The crust is actually made up of different pieces which scientists call plates. Most earthquakes happen where these plates touch one another. When the plates move or when one plate slides underneath another, they grind against each other. This makes the earth’s crust shake or vibrate. This release of energy is an earthquake.
Most of the United States is on one of the earth's plates. The edges of this plate are along the Pacific Ocean and in the middle of the Atlantic Ocean. Most large earthquakes in the United States happen on the western edge of the plate in Alaska and California. New York sometimes does have small earthquakes that have a different cause.
During the last Ice Age, huge layers of ice pressed down on the bedrock across most of New York State. Once the ice was gone, the rock started to slowly rebound, causing small earthquakes to happen. This is a little like when someone sits on a bed, making the mattress sag. When the person stands back up, the mattress bounces back up. With rock, the bouncing back up happens much slower and it is still happening.
Any earthquake that happens near or under a large body of water can cause waves. These waves are called tsunamis. You can make a model of a tsunami when you are in the bathtub. Just move your arm or leg in the water and you will make waves. The waves may not seem like much until they reach the side of the tub. Then they may splash high. The same thing happens in the ocean. A tsunami may not seem like much until it reaches land where it may become a very tall wave or even several very tall waves.
There are systems of seismographs to sense and measure earthquakes in both the Pacific and Atlantic Oceans. If a major earthquake happens, there is a system in place to warn communities about possible tsunamis so that people can move to safer paces. It uses the radio and TV systems of the weather service (NOAA) to get warnings out to the public.
On December 26, one beach was cleared before the waves hit because a ten-year old student recognized the sudden odd drop in water levels as the first sign of an approaching huge wave. She told her parents that she had learned in science class that they had only 10 minutes to get to high ground. They told a life guard and the whole beach full of swimmers and sunbathers was cleared and lives saved.
To learn more about earthquakes, you can visit some of the sites listed below.