Tsunamis are waves, but they are far different from normal waves that occur every day in the ocean. A normal wave is created by the pull of the moon’s gravity, but tsunamis are a series of great sea waves that are created by a shock from underwater. The most common causes of tsunamis are underwater earthquakes, landslides or volcanic eruptions. On Sunday, 26th December, 2004, a 9.0- magnitude earthquake occurred under the Indian Ocean near the west coast of the Indonesian island of Sumatra. It displaced a large amount of water, and sent shock waves in every direction, resulting in a series of 30-foot waves traveling up to 500 miles per hour. These high speeds cause the waves to be very destructive. They travelled unnoticed at first because they were not visible on the surface, a common pattern in the occurrence of tsunamis. 16. Which of the following best expresses the main idea of the passage? A. Normal waves and tsunamis. B. Characteristics of ocean waves. C. How is tsunamis is caused. D. How to predict tsunamis. 17. According to the passage, what can create a tsunamis? A. Shocks that occur underwater. B. The pull of the moon’s gravity. C. A large rock dropping into the ocean. D. It is not known. 18.The word magnitude in the text is closet in meaning to……. A. destructive B. danger C. size D. importance 19. What caused the tsunamis of December 26, 2004? A. An earthquake. B. An underwater volcanic eruption. C. The moon’s gravity. D. None of the above. 20. Which of the following is not true according to the passage? A. The most common cause of a tsunamis is an underwater earthquake. B. Tsunamis may not be visible on the surface if the ocean is deep. C. Tsunamis occur every day in the ocean. D. Tsunamis are unusual because they are not created by the pull of the moon’s gravity.