Q. 1 Where do waves in the ocean get their energy from? 
 Answer Key Points: -
1) Wind provides energy to the waves. Wind causes waves to travel in the ocean and the energy is released on shorelines.
2) The motion of the surface water seldom affects the stagnant deep bottom water of the oceans.
3) As a wave approaches the beach, it slows down. This is due to the friction occurring between the dynamic water and the seafloor.
4) Waves continue to grow larger as they move and absorb energy from the wind.
5) Most of the waves are caused by the wind driving against water. When a breeze of two knots or less blows over calm water, small ripples form and grow as the wind speed increases until white caps appear in the breaking waves.
Q. 2 White the characteristics of waves in the oceanic water. 
 Answer Key Points: - 
Characteristics of waves in the oceanic water are: -
1) The highest and lowest points of a wave are called the crest and trough.
2) Wave height is the vertical distance from the bottom of a trough to the top of a crest of a wave.
3) Wave amplitude is one-half of the wave height.
4) Wave period is merely the time interval between two successive wave crests.
5) Wavelength is the horizontal distance between two successive crests.
6) Wave speed is the rate at which the wave moves through the water, and is measured in knots.
7) Wave frequency is the number of waves passing a given point during a one- second time interval.
Q. 3 Give the Classification of tides on the basis of the frequency.
 Answer Key Points: -
1) Semi-diurnal Tide: - It is the most common tidal pattern, featuring two high tides and two low tides each day. The successive high or low tides are almost of the same height.
2) Diurnal Tide: - There is only one high tide and one low tide during each day. The successive high and low tides are approximately of the same height.
3) Mixed Tide: - Tides having variations in height are known as mixed tides. These tides generally occur along the west coast of North America and on many islands of the Pacific Ocean.
Q. 4 Give the Classification of tides on the basis of their height. 
 Answer Key Points: -
Tides do not rise to the same height every day. They are influenced by the relative position of the moon and the sun with respect to the Earth. Types of tides based on height are: -
1) Spring Tides: - Spring tides occur during the New moon and full moon when the Earth moon and sun are in straight line. At this time the combined gravitational forces of the sun and the moon are stronger and tides are highest. Spring tides occur twice in a month.
2) Neap Tides: - Neap tides occur during the first quarter and the last quarter when the Sun, Earth and Moon are at right angles. During this time the gravitational force of the Moon is offset by the gravitational force of the Sun and the tides are not so high.
Q. 5 Give the importance of tides. 
 Answer Key Points: -
1) They are helpful to the navigators in the navigation activities.
2) A high tide helps shipping vessels to enter shallow ports.
3) A high tide brings in fish which is netted by fishermen.
4) Tides clear silt deposits from the mouth of rivers keeping them free for water transport.
5) Tidal energy is being used to produce electricity.
6) Tides live many shells and other sea products on the shore.
7) Tides keep the sea water in motion this keep the water clear and avoids its freezing many ports in England do not freeze in winters due to tides.
Q. 6 Heating of solar energy, wind, gravitation and Coriolis force affect the ocean currents. Explain Or
What are the causes of currents?
 Answer Key Points: -
The general movement of a mass of Oceanic water in a definite direction is called Ocean Current. Ocean currents are like river flow in oceans. They are caused by two types of forces called: -
 Primary Forces: -
1) Heating by Solar Energy: - Heating by solar energy causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope. The flow is normally from east to west.
2) Wind (Atmospheric Circulation): - Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course.
3) Gravity: - Gravity tends to pull the water down the pile and create gradient variation.
4) Coriolis Force: - The Coriolis force intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. These large accumulations of water and the flow around them are called Gyres. These produce large circular currents in all the ocean basins.
 Secondary Forces: -
1) Temperature: - Cold-water ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. Warm-water currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water.
2) Salinity: - Differences in water density affect vertical mobility of ocean currents (vertical currents). Water with high salinity is denser than water with low salinity and in the same way cold water is denser than warm water. Denser water tends to sink, while relatively lighter water tends to rise.
Q. 7 Why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes? 
 Answer Key Points: -
1) At Equator heating by solar energy causes the water to expand, but deep waters sink into the deep ocean basins at high latitudes, where the temperatures are cold enough to cause the density to increase.
2) The higher the salt content of water, the denser it is. Dense water is heavier than less dense water, and thus will sink because of gravity.
3) This causes a very slight gradient and water tends to flow down the slope.
4) So near the equator the ocean water is about 8 cm higher in level than in the middle latitudes.
Q. 8 Explain different types of ocean currents. Or
Differentiate between warm currents and cold currents.
 Answer Key Points: -
 On the Basis of Depth: -
Surface Water Currents
Deep Water Currents
1. Definition
Surface ocean currents are caused by solar heating and wind. Solar heating causes water to expand.
Deep ocean currents are caused by the interaction between temperature and water density.
2. Size
Surface currents constitute about 10 percent of all the water in the ocean. Surface currents occur in the upper 400 meters of the ocean.
Deep water currents make up the other 90 percent of the ocean water.
 On the Basis of Temperature: -
Cold Currents
Warm Currents
1. Definition
They flow from equatorial regions to high latitudes.
They flow from polar region to low latitudes.
2. Nature
Its temperature is higher than the surrounding water.
Its temperature is below than the surrounding water.
3. Effects
It raises the temperature of coastal areas and is observed normally on the east coast of lower and middle latitude.
It reduces the temperature of the coastal area and is observed on the west of continent in lower and middle latitudes.
4. Results
Winds passing over warm currents absorb a good amount of moisture and bring heavy rainfall on the coastal areas.
Winds passing over cold currents become dry and little rainfall on the coastal area.
5. Benefits
Warm currents are of great help to navigation because they melt ice bergs.
Cold currents reduce navigation because they create ice bergs.
6. Feature
Warm currents keep the ports open in the polar regions free from ice.
Cold currents make the parts un-operational in lower latitudes as they are ice bound.
Q. 9 How do currents affect the temperature? How does it affect the temperature of coastal areas in the N. W. Europe?
 Answer Key Points: - 
Effects of currents influenced by temperature.
1) Warm currents make the place warmer whereas the cold currents make the place colder. E.g. Warm currents of Kuroshio make the southern Japan less cold in winter whereas the cold current of Koroshio makes the winter longer and severe in north Japan.
2) Winds passing over warm currents absorb lot of moisture and cause heavy rainfall in coastal areas. On the other hand winds passing over long currents do not get any warm currents as such; they make the climate of coastal areas dry. This is the reason why hot deserts are located near the coastal areas from where the cold current passes.
3) The places where cold current and warm current near the coastal areas are found in abundance are rich fishing ground. For example, Newfoundland, the east coast of North America where Labrador Current and Gulf Stream meet.
Q. 10 How is the movement of currents influenced by prevailing winds? Give examples.
 Answer Key Points: -
1) The prevailing winds are the winds that usually blow in the same direction, Influence Ocean currents because the wind causes friction on the water surface causing the water to move in the same
direction as the wind.
2) Some prevailing winds are called “Trade Winds” because merchants on sailboats used these regular winds to sail across the Indian Ocean or Atlantic Ocean to trade their goods.
3) The wind made sailing to some places very easy and other places very difficult.
4) Some of these regular winds change direction during certain months. This is called monsoon.
5) Monsoon winds blow one direction from May to October, and then change directions from November to April, which allowed the merchants to sail home in Monsoon areas of the world.
6) The monsoon winds mainly effects South Asia (India). Indian traders sailed west to Africa in the summer and east back to India in the winter.