Rogue waves .
1 The Cape of Good Hope, on the southern tip of South Africa, is on a major shipping route. Bartolomeu Dias, the first European to reach the Cape in 1488, named it the Cape of Storms. Since then, over 1,000 ships have sunk in these treacherous waters. There have been reports of many rogue waves. These are unusually large, dangerous, unexpected waves. In the past, these reports had been written off as sailors tales. Now, scientists know that these legends are true.
2 Rogue waves arise as the wind blows across the sea. They begin as very small waves, just a few tenths of an inch across. When the wind increases, the waves get larger. As they travel across the ocean, some waves move faster than others. When they catch up with each other, they combine and grow until they produce giant waves.
3 Captain Dye Davies is a leading expert on wave damage. Hes seen firsthand the damage these waves can do. Following is an interview with the captain.
4 Ive been involved with five major incidents on the Cape. Ive seen 365,000 ton ships lose up to 5,000 tons of steel because of rogue waves.
5 Since 1990, over 20 big ships navigating this busy shipping route have been crippled by giant waves. The Mimosa was one of them. A huge hole was punched in her side.
6 In 1991, the Atlas Pride lost most of her bow, and the waves took out 5,500 tons of steel. One year later, the tanker Katina P had two holes smashed in her side by a giant rogue wave.
7 The captain of the Katina P later told me, This wave came from nowhere and just overwhelmed the ship, and she went down.
8 For a while, no one could explain why there are so many rogue waves here. Finally, scientists discovered a pattern. The damaged ships all lay in the path of one of the worlds strongest ocean currents, the Agulhas current.
9 This current runs around the Cape and can flow up to 10 miles per hour. Like the jet stream does for airliners, this ocean current can cut travel time for ships. It can save up to a day as ships round the coast of Southern Africa, but it also comes with a high risk.
10 Scientists have discovered that when the wind blows in the opposite direction to the current, it pushes against the waves and slows them down. This allows waves behind to catch up. As the waves combine, they can grow to record heights. Sailors have reported waves up to 100 feet that appear out of nowhere! These are the rogue waves that have turned this coastline into a ships graveyard. Now that scientists have discovered exactly why this part of the world is so hazardous, most ships take a safer, slower route, 100 miles further south.
1 Tsunami is a Japanese word that means harbor wave. Tsunamis are large, powerful waves caused by undersea or coastal earthquakes, volcanoes, or landslides. These events can release energy so great, that high-frequency waves travel outward in all directions for thousands of kilometers. Tsunamis can cross an ocean in less than 24 hours and unleash amazing, destructive force.
2 In 1960, the 20th centurys largest earthquake occurred off the coast of South America. It created one of the largest tsunamis ever. The waves reached Hawaii 15 hours after the earthquake. Sixty-one people died. After traveling halfway around the world, the waves hit Japan. The Japanese town, Ofunato, was destroyed, and there was horrible loss of life and property.
3 In 1983, a thin, barely visible line appeared on the horizon. Soon another tsunami was assaulting the Japanese coast. This one was triggered by a powerful earthquake that occurred in the sea off the Japanese shore. The tsunami swept down the coast, surging into inlets and harbors as it passed. It broke thick mooring ropes like threads and set boats adrift. One hundred people drowned, and many houses and boats were destroyed by this incredible tsunami. Surprisingly, for all its fury, a tsunami has the same basic wave characteristics as any wave you may see in the ocean.
What Causes Tsunamis?
4 Ocean waves look like they are taking water with them as they move. But waves arent really moving water; theyre moving energy. The energy within the wave moves through the water. Tsunamis, like all waves, are made of a series of crests and troughs. Unlike typical ocean waves, tsunamis usually have longer wavelengths. Normal ocean waves are caused when wind transfers some of its energy as it pushes along the waters surface. But tsunamis are caused by three different types of high-energy events.
5 Usually, tsunamis are caused by underwater earthquakes that violently shake and move the seafloor. The water above the point of the earthquake is driven up and down by the energy that moves the ocean floor. Another cause of tsunamis is underwater landslides. As underwater rocks fall, they create a tsunami that travels outward from the origin of the slide. These landslide-generated tsunamis are usually limited to a certain area. The third cause of tsunamis is underwater or coastal volcanic activity. These eruptions result in great amounts of earth moving underwater. The moving earth moves great volumes of water and generates the high-powered tsunami waves. Although volcano-generated tsunamis are less common, they can be just as deadly.
6 In the open ocean, tsunamis can travel at speeds up to more than half the speed of sound! Tsunamis in the open ocean are sometimes not very high. Someone on a ship might not even feel one of the waves as it passes beneath them, but when tsunamis approach the shore, the rising seafloor forces the wave to rise. It builds, then breaks into a huge surge of water. Tsunamis can sometimes reach as high as 30 meters above sea level! The height of the wave depends almost entirely on the offshore landscape. Waves usually rise to greater heights along gently sloping shores.
Read the prompt below and then write your response.
You have read two passages about rogue waves and tsunamis. You learned that rogue waves and tsunamis are enormous, sometimes measuring over 100 feet tall. Their power and speed can cause massive amounts of destruction.
Based on what you read, write a multi-paragraph, informative essay comparing rogue waves and tsunamis. Support your comparison with facts and details from the passages you read.
Your writing will be scored based on the development of ideas, organization of writing, and language conventions of grammar, usage, and mechanics.
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