(i) Precipitation is defined as the deposition of moisture from the atmosphere onto the earth’s surface. This may be occur in the form of rain, hail, frost fog, sleet or snow etc.
(ii) The process by which water changes continuously change its form and circulates between oceans, atmosphere and land is called as the water cycle.
(iii) Factors affecting the heights of the waves are as follows:
- Speed of wind
- Duration of wind
- Distance the wind blows over water
- Earthquakes
- Volcanic eruption
- Underwater landslides
(iv) Factors affecting the movement of ocean water are as given below:
- Temperature
- Earthquake or volcanic eruption
- Gravitational pulls of the sun and the moon
- Underwater landslides
- Rotation of the earth
(v) The rhythmic rise and fall of ocean water twice a day is known as tide. Tides are caused due to the gravitational pull that is exerted by the sun and the moon on the earth’s surface.
(vi) Ocean currents are defined as streams of water flowing constantly on the oceanic surface in definite directions.
(i) Oceanic water is salty because it obtains large amount of dissolved salts. Most of the salt is sodium chloride or contains the common table salt that we eat.
(ii) The quality of water is deteriorating as reasons given below:
- Garbage that we throw in the river.
- Chemicals pollutes water that are released from industries.
- Residues of the harmful insecticides and pest resistant’s flowing in from the fields.
- Unburnt or half burnt corpses of men and animals thrown in water bodies.
(i) (a) water cycle
(ii) (b) equator
(iii) (a) tide
(i) Caspian sea (a) Largest lake
(ii) Tide (b) Periodic rise and fall of water
(iii) Tsunami (c) strong seismic water
(iv) Ocean currents (d) Streams of water mov