The ocean never seems to sit still. Its waves rise and fall.On beaches they push forward and fall back. But what makes ocean water into waves?
Most waves are created by the wind. The wind blows along the surface of the water and forces waves in the same direction. The top of a wave is called the “crest,” and the lowest part in between the crests is known as the “trough.” When waves roll through the open ocean, they’re called “swell.” As they reach the shore, their crests get higher and closer together and finally topple over. Then they’re called “breakers” or “surf.” A gentle wind makes long waves that don’t rise very high. But stronger winds push harder on the water and create taller waves. Big storms mean strong winds, and that means huge, powerful waves. Major ocean storms, called “hurricanes” or “typhoons,” can cause enormous waves. Some are so big they can smash oceanside houses into pieces or tip over ships that get in their way. During violent storms waves have been known to reach to the tops of lighthouses and to toss boats completely out of the water. The most destructive waves are tsunamis, but they’re quite different from other waves. Tsunamis (from the Japanese for “harbor wave) also wrongly called “tidal waves”,aren’t caused by tides or by the wind. These huge waves are created by underwater earthquakes or volcanic eruptions. A tsunami is a large destructive wave created by the shock from an earthquake or volcanic eruption. The impact of a meteorite could also create a tsunami. Tsunamis travel fast and have the force to destroy entire coastal communities within moments.
A tsunami can travel at speeds of 450 miles per hour or more (as fast as a jet plane) and packs tremendous force. As the tsunami approaches land, it grows larger. It continues to travel until its energy is completely used up. All low-lying coastal areas are vulnerable to a tsunami disaster. In December 2004 an earthquake caused a major tsunami in the Indian Ocean. The earthquake struck off the coast of Indonesia. Two hours later, waves as high as 30 feet hit coastal areas some 750 miles away. The tsunami killed more than 200,000 people….
If you’ve ever looked at a rainbow and wondered how all those bright
colors got in the sky, you’re not alone.
The ancient Greeks thought these arcs of color were signs from the gods to warn people that terrible wars or storms were going to happen. The Norse people believed a rainbow was a bridge the gods used to walk down from the sky to the Earth. Other legends said there was a pot of gold waiting at the end of a rainbow. But as beautiful as rainbows are, they aren’t magic. And they aren’t solid enough to walk on. In fact, a rainbow is just colored light. The seven colors are always the same and appear in the same order: red, orange, yellow, green, blue, indigo (a very deep blue), and violet. The name “Roy G. Biv” helps you remember the first letters and the order of the colors.
Rainbows often appear after or at the end of a storm, when the Sun is shining again but there is still some rain in the air. The sunlight looks white, but all seven rainbow colors are mixed together in it. So when a beam of sunlight passes through raindrops, it’s broken into the seven different colors. But you don’t have to wait for rain to see rainbows. You can make your own rainbow.
Place the glass of water in direct sunlight and then submerge a small mirror halfway in the water. Half of the mirror should be below the water line and half above the water line. Tilt and rotate the mirror until you catch the sunlight, which will then be refracted through the water to create the rainbow colors.