What Causes Waves?

The winds cause waves on the surface of the ocean (and on lakes). The wind transfers some of its energy to the water, through friction between the air molecules and the water molecules. Stronger winds (like storm surges) cause larger waves.

Waves of water do not move horizontally, they only move up and down (a wave does not represent a flow of water). You can see a demonstration of this by watching a floating buoy bob up and down with a wave; it does not, however, move horizontally with the wave.

Tsunamis (sometimes called tidal waves) are different from surface waves; they are usually caused by underwater earthquakes, volcanic eruptions, or landslides.

What causes the tides?

Tides are periodic rises and falls of large bodies of water. Tides are caused by the gravitational interaction between the Earth, the Moon and the Sun. The gravitational attraction of the moon causes the oceans to bulge out in the direction of the moon. Another bulge occurs on the opposite side, since the Earth is also being pulled toward the moon (and away from the water on the far side). Since the earth is rotating while this is happening, two tides occur each day. Isaac Newton was the first person to explain tides scientifically.

1. How do the waves appear on the surface of water?

1. through transmitting solar energy;

2. due to rubbing the smallest particles of the air and the water;

3. due to the collision of various tides.

2. What are storm surges?

1. Tsunamis.

2. Waves caused by hurricanes.

3. Ripples.

3. Do the waves move in the flow of water?

1. Yes, they move horizontally.

2. No, they move from side to side.

3. No, they move vertically.

4. Tsunamis are sometimes caused by

1. a mass of rock and earth moving suddenly and quickly down a steep slope;

2. strong winds;

3. hurricanes.

5. The reason of the tides is

1. gravitational impact of the Mars.

2. natural attraction between the Moon and the Earth;

3. gravitational interaction between the Sun and the Earth.

6. The gravitational attraction forces the oceans to

1. stick out from something in a round shape;

2. move the waves horizontally;

3. form storm surges.

(Based on http://www.enchantedlearning.com/subjects/ocean/Waves.shtml,

http://www.enchantedlearning.com/subjects/ocean/Tides.shtml)

Task 7. Reading. Tsunami

7.1 Match the words to their definitions. One of the definitions is extra:

1. a huge tropical cyclone that originate over oceans near the equator, such as the Caribbean Sea and the Gulf of Mexico. One of the most destructive elements of it is the huge waves that are formed because of the strong winds and heavy rains.

2. one of weather’s most deadly and fascinating forces. Even though they are often limited by size (not being more than one kilometre wide at most) they leave vast areas of destruction and death behind them. They are also called twisters or cyclones.

3. It has incredible energy because of the great volume of water affected. Towering walls of water have struck populated coastlines with such fury that entire towns have been destroyed.

4. a vent in the earth through which hot gases and molten rock rise to the surface.

5. shaking of the ground caused by the sudden dislocation of material within the earth's outer layer, or crust.

6. a period or condition of unusually dry weather within a geographic area where rainfall is normally present.

7. discharge of electricity between rain clouds or between a rain cloud and the earth. It is usually seen as an arc of extremely bright light which can be many kilometres in length, however, there are other forms as well.

(Based on http://library.thinkquest.org/16132/frames.html)

7.2 Answer the following questions:

1. What are the most destructive natural disasters? (select one or more from the table)

2. Is there a tsunami in this list? Why?

3. What do you know about the destruction from tsunami?

7.3 Study the following abbreviations and measures:

1. mph – miles per hour; do not confuse with MPH - Master of Public Health.

2. kph – kilometers per hour; 1 Mile per Hour = 1.609344 Kilometers per Hour.

3. km/hr or km·h−1 – kilometers per hour

4. Richter scale – a numerical scale for expressing the magnitude of an earthquake on the basis of seismograph oscillations. The more destructive earthquakes typically have magnitudes between about 5.5 and 8.9; it is a logarithmic scale and a difference of one represents an approximate thirtyfold difference in magnitude.

7.4 Fill in the prepositions using the tips in brackets. Then scan the text to check:

1. travels ___ up to 90 km/hr (expressing location or arrival in a particular place or position);

2. a system of sirens ___ the beach (located somewhere in the general surface area of (a place));

3. crashing ___ in the water (expressing movement or action with the result that someone or something makes physical contact with something else);

4. warning systems exist in many places ___ the world (on every side of).

5. the distance ___ crest to crest (indicating the starting point of a specified range on a scale).

6. run ___ higher ground or inland (in the direction of getting closer to achieving (a goal)).

7.5 Read the following text and decide whether the statements after it are true (T) or false (F):