Waves (波浪) are beautiful to look at, buthuge waves are greatly harmful to ships at sea, as well as houses and buildingsnear the seaside. What causes waves? Most waves are caused by winds' blowingover the surface of the water. The sun heats the earth, causing the air to riseand the winds to blow. The winds blow across the sea, pushing little waves intobigger and bigger ones.

    The sizeof a wave is decided by how strong the wind is, how long it blows, and howlarge the body of the water is. In a smallbay, big waves will neverbuild up. But at sea the wind can build up big, powerful waves.

    It isbelieved that the height of a wave (in metres) will usually be no more thanone-tenth of the wind's speed (in kilometres). In other words, when the wind isblowing at 120 kilometers an hour, most waves will be 12 meters high or less.Of course, some waves may came together to form big waves that are much higher.