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PASSAGE 30

ROGUE WAVES

Rogue waves are extremely large waves that are more than double the average height of most waves.

According to mathematical calculations and various personal accounts, rogue waves can reach remarkable

heights. They appear unexpectedly in calm waters and can do major damage, even to large ships. Unlike

tsunamis, which are practically undetectable in deep water, rogue waves only occur far out at sea. Stories

about rogue waves have circulated amongst sailors for centuries, but it was not until recently that

scientists confirmed they actually exist. What they still are not sure of, however, is what causes them.

Some instances of rogue waves have been explained by the interactions of normal wave patterns with

ocean currents. Scientists believe that it is possible for waves to reach the heights described when they

come into contact with strong ocean currents. The wave heights increase significantly when a normal

wave reaches a current head on. In other words, the wave is built up by the power of the current. This

explanation was first proposed after scientists observed a high incidence of rogue waves in the ocean

surrounding the southern tip of Africa. In fact, since 1990, at least twenty ships have encountered the

waves, which reportedly reached up to 190 feet. The waves are thought to be caused by wave interactions

with the strong Agulhas Current, which runs southbound along the east coast of the continent.

Ocean currents may be responsible for rogue waves in some parts of the world, but scientists have

confirmed their existence even in areas that are not affected by strong currents. In those cases, scientists

think that the waves are caused by wave reinforcement. Wave reinforcement is when two or more waves

join together to form one massive wave. When the waves are joined, each height is added to the others.

For example, if a ten-foot wave comes into contact with a fifteen-foot wave, the resulting wave will be

twenty-five feet tall. According to some evidence, it is possible that many waves can join together, which

would create rogue waves. Scientists still do not understand which circumstances cause wave

reinforcement, but many propose that the reason rogue waves appear suddenly is because they are formed

by multiple smaller waves randomly.

Question 1. The passage mainly discusses

.

A. the theories of how rogue waves are formed

B. instances of rogue waves that have been explained

C. the increasingly high waves

D. the circumstances causing wave reinforcement

Question 2. Why does the author mention tsunamis?

A. To explain why rogue waves cannot be predicted

B. To describe the similar mechanism that causes rogue waves

C. To note that rogue waves and tsunamis are unrelated

D. To show that rogue waves are comparable to tsunamis

Question 3. Which of the following is NOT true, according to the passage?

A. Rogue waves can appear unexpectedly in calm waters.

B. Scientists confirmed that rogue waves actually exist only recently.

C. Rogue waves and tsunamis are mostly undetectable in deep water.

D. Rogue waves can reach remarkable heights.

Question 4. The author uses the Agulhas Current as an example of

.