Ans. Quality of water is deteriorating because
i. River water, which is our primary source of water, gets contaminated due to various reasons such as direct disposal of sewage by municipalities, excessive discharge of industrial pollutants, use for daily chores like washing, bathing, livestock bathing, garbage disposal, etc.
ii. Water sourced from groundwater too has deteriorated due to the excessive use of pesticides & insecticides in agriculture, which seep into the groundwater as well as get washed away into the rivers.
i. Tsunami is a Japanese word that means “Harbour waves” as the harbours get destroyed whenever there is tsunami.
ii. An earthquake, a volcanic eruption or underwater landslides can shift large amounts of ocean water.
iii. As a result a huge tidal wave called tsunami, that may be as high as 15m., is formed. The largest tsunami ever measured was 150m. high. These waves travel at a speed of more than 700 km. per hour.
iv. The tsunami of 2004 caused wide spread damage in the coastal areas of India. The Indira point in the Andaman and Nicobar islands got submerged after the tsunami.
Ans. Ocean Currents
i. Ocean currents are streams of water flowing constantly on the ocean surface in definite directions.
ii. The ocean currents may be warm or cold. Generally, the warm ocean currents originate near the equator and move towards the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes. The Labrador Ocean current is cold current while the Gulf Stream is a warm current.
iii. The ocean current influence the temperature conditions of the area. Warm currents bring about warm temperature over land surface. The areas where the warm and cold currents meet provide the best fishing grounds of the world. Seas around Japan and the eastern coast of North America are such examples. The areas where a warm and cold current meet also experience foggy weather making it difficult for navigation.
Ans. The movements that occur in oceans can be broadly categorised as: waves, tides and currents.
Waves - When the water on the surface of the ocean rises and falls alternately, they are called waves. Waves are formed when winds scrape across the ocean surface. The stronger the wind blows, the bigger the wave becomes.
Tides - The rhythmic rise and fall of ocean water twice in a day is called a tide. It is high tide when water covers much of the shore by rising to its highest level. It is low tide when water falls to its lowest level and recedes from the shore. The strong gravitational pull exerted by the sun and the moon on the earth’s surface causes the tides.
Ocean Currents - Ocean currents are streams of water flowing constantly on the ocean surface in definite directions. The ocean currents may be warm or cold. Generally, the warm ocean currents originate near the equator and move towards the poles. The cold currents carry water from polar or higher latitudes to tropical or lower latitudes. The Labrador Ocean current is cold current while the Gulf Stream is a warm current.
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