Submarine Earthquakes, Part II

Submarine Earthquakes, Part II
Reading Level
     edHelper's suggested reading level:   grades 5 to 7
     Flesch-Kincaid grade level:   10.42

     challenging words:    gauges, geologists, magnitude, mid-ocean, occurrence, oceanographers, seismologists, margin, striking, continental, radiate, frequently, article, destruction, series, affected
     content words:    Submarine Earthquakes, Tsunami Warning Centers, Pacific Ocean, Author Note, On December, Indian Ocean, Sri Lanka

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Submarine Earthquakes, Part II
By Trista L. Pollard

1     As you read in the article, Submarine Earthquakes, Part I, underwater earthquakes can cause tsunamis (pronounced soo-nahm-ee). The word "tsunami" comes from the Japanese language, and it means "harbor wave." People tend to call tsunamis "tidal waves"; however, these waves really are not formed because of tides. In this article we will explore the characteristics of tsunamis and the destruction they cause.
2     Tsunamis are a series of catastrophic ocean waves that are formed after submarine earthquakes, volcanic eruptions, landslides, or asteroids striking the earth. Asteroids may not be a normal occurrence; however, earthquakes, volcanic eruptions, and landslides under the ocean happen more frequently than you realize. This is why seismologists at Tsunami Warning Centers in Honolulu, Hawaii, and Palmer, Alaska, constantly monitor or keep track of underwater disturbances in the Pacific Ocean (the area where tsunamis occur most often) and surrounding areas.
3     Tsunamis occur most often after submarine earthquakes that measure over a 6.5 magnitude on the Richter scale. Underwater volcanic eruptions in the mid-ocean mountains and ridges and landslides in the continental margin can cause submarine earthquakes. Once the earthquake occurs and the ocean floor is disturbed, waves travel outward in all directions from the focus of the earthquake. Imagine throwing a rock into a lake on a summer day. When the rock breaks the surface of the water, ripples appear and radiate outward from the point where the rock entered the water. The waves then travel through the open sea. In the open ocean, these waves may reach a speed up to 500 miles per hour (720 kilometers per hour). Their wavelengths may also be up to several hundred miles. One surprising fact is that their heights at this point may only reach less than three feet (one meter). Even a ship at sea would not notice this tsunami wave.

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