1. Multiple choice questions.
(i) Upward and downward movement of ocean water is known as the :
(a) tide (b) current (c) wave (d) none of the above
(ii) Spring tides are caused :
(a) As result of the moon and the sun pulling the earth gravitationally in the same direction.
(b) As result of the moon and the sun pulling the earth gravitationally in the opposite direction.
(c) Indention in the coast line.
(d) None of the above.
(iii) The distance between the earth and the moon is minimum when the moon is in :
(a) Aphelion (b) Perigee (c) Perihelion (d) Apogee
(iv) The earth reaches its perihelion in:
(a) October (b) September (c) July (d) January
2. Answer the following questions in about 30 words.
(i) What are waves?
Ans. Waves are actually the energy, not the water that moves across the ocean surface. Wind causes waves to travel in the ocean and the energy is released on shorelines.
(ii) Where do waves in the ocean get their energy from?
Ans. Wind provides energy to the waves.
(iii) What are tides?
Ans. The periodical rise and fall of the sea level, once or twice a day, mainly due to the attraction of the sun and the moon.
(iv) How are tides caused?
Ans. Tides are said to be caused by the gravitational pull of the sun and moon.
(v) How are tides related to navigation?
Ans. One of the main benefit of high tide is that it helps in navigation. When high tides occur the water level rises up. This is the time when it is safe for the large ship to enter and leave the harbor. Large ship can easily sail in water when there is high tide.
3. Answer the following questions in about 150 words.
(i) How do currents affect the temperature? How does it affect the temperature of coastal areas in the N. W. Europe?
Ans. Ocean currents act like a conveyor belt, transporting warm water and precipitation from the equator toward the poles and cold water from the poles back to the tropics. Thus, ocean currents regulate global climate, helping to counteract the uneven distribution of solar radiation reaching Earth’s surface. The North Atlantic Drift, carrying warm equatorial waters northwards, increases temperatures along the coast of north-western Europe and helps to keep coastal areas warm throughout the year.
(ii) What are the causes of currents?
Ans. Ocean currents are caused due to temperature variation, salinity, prevailing winds, Coriolis force and topography of ocean floor. Watch this video you will understand the factors responsible for the causes and movement of ocean water / currents.