Class 7, Geography
Questions covered are
Write short note on Water?
Define Water Cycle?
Write about the Water cycle process?
How water is distributed in water bodies ?
Why ocean water is so saline?
Why tropical oceans are more saline?
Write about the temperature of ocean water?
What are the four major oceans?
How Ocean serve as a major role in the life of humans?
What are the three main factors responsible for the movement of ocean water?
What are the three types of movement of Ocean?
How waves are formed?
What is Crest and trough in a wave?
What is Wave height and wavelength?
How Tsunamis are caused?
What are Tides?
What are Spring tides?
What are Neap Tides?
List a few advantages of tides?
What are Ocean Currents?
What are Drifts?
What are the reasons for the formation of Ocean currents?
Write the difference between warm currents and cold currents?
What are the effects of ocean current?
Get some importance of ocean current?
***************************************************************************************************************
Write short note on Water?
- Earth has 71% of surface water and 29% of land.
- Water is found in Oceans, Seas, Lakes, River, Pond and Underground. So Earth is called as Blue Planet or Watery Planet.
- The Watery part of Earth is called as Hydrosphere.
- It includes ice sheets of Polar, High Mountain regions, underground, Water vapour in atmosphere.
Define Water Cycle?
The constant circulation of water from Earth to atmosphere and back to Earth again is known as Water cycle.
Write about the Water cycle process?
- Water in Seas, Rivers, Lakes, Pond evaporates due to heat of sun.
- Water vapour rises up.
- Air in the atmosphere is cooler.
- In atmosphere, water vapour condenses to form water droplets.
- Water droplets join together to form clouds.
- As clouds get cooled, water drops become bigger.
- When clouds become too heavy, they fall on earth as rain.
- This process is called as precipitation.
- Water cycle is main source of groundwater.
- Water cycle is an ongoing process. It never ends.
How water is distributed in water bodies ?
- 3/4th of the Earth’s surface is covered by water.
- 97% of the total Earth water is found in oceans and seas.
- Fresh water is 3% out of which 2 % of the total water is in frozen ice caps and glaciers.
- So only 1% is fit for consumption and is found in lakes, rivers, streams etc.
- Groundwater constitute 0.68 % water vapour constitutes 0.0019 % of total water.
Why ocean water is so saline?
- The water in the oceans have variety of salts, minerals dissolved in it.
- Some of them are Potassium, Magnesium, Calcium, Sodium Chloride.
- Measure of the salt content is called as salinity.
- Average salinity is 35 grams per 100 grams of water.
Why tropical oceans are more saline?
- Amount of salinity is due to increased evaporation.
- When the evaporation rate is high, all water are evaporated and salts are left behind.
- So due to active evaporation under clear sky tropical oceans are more saline.
- How salinity level are lower than equator and polar regions?
- in Equator, salinity levels are lower due to heavy rainfall. Since the rainwater is added to the salty ocean, salinity is low.
- In Polar region, salinity is reduced due to lack of evaporation and addition of water due to melting ice.
Write about the temperature of ocean water? Main source of temperature is heat of the sun.
Near the equator Ocean water is warmer and near polar regions it is cooler as temperature decreases.
What are the four major oceans?
Oceans are large water bodies on the surface of Earth.
Four major oceans are
- Pacific Ocean
- Atlantic Ocean
- Indian Ocean
- Arctic ocean
How Ocean serve as a major role in the life of humans? Oceans are prime source of water cycle.
- Ocean serves as means of transport.
- Oceans are the storehouses of marine food and home for many marine animals.
- Ocean tides and waves are used to generate powers.
- Climate of landmasses are greatly influenced by oceans.
What are the three main factors responsible for the movement of ocean water? The three main factors are
- Effect of planetary winds
- Density variation in sea water and temperature difference.
- Difference in salinity of ocean water.
What are the three types of movement of Ocean?
The three types of movement of ocean are
Waves, Tides and Ocean currents.
How Waves are formed?
- Wind actions are responsible for creating waves.
- Waves can be described as rise and fall of water on the surface of oceans.
- When the surface water is disturbed by blowing wind, it result in the formation of waves.
What is Crest and trough in a wave?
- The rise in a wave is known as Crest.
- The fall in the wave is known as Trough
What is Wave height and wavelength?
- The vertical and the horizontal distance between the crust and trough is known as wave height.
- The horizontal distance between two crest or two trough is known as wavelength.
How Tsunamis are caused?
- During heavy storm or strong volcanic eruption or earthquakes huge waves are formed These are called as Tsunamis.
- These are 20 to 30 m high and travel at the speed of 500 to 1000 km per hour and cause great destruction.
What are Tides?
- A strong gravitational pull is exerted by the sun and moon on Earth.
- This leads to alternate rise and fall in the level of the water called as Tides.
- Rise in water level is high tide and fall in water level is called as low tide.
What are Spring tides?
During full and New Moon days, Sun, Moon and Earth are in the same line and tides are highest.
These are called as spring tides.
What are Neap Tides?
When Moon is in the first and last quarter gravitational pull of Sun and Earth draws the ocean water in diagonally opposite directions. These are called as Neap Tides.
List a few advantages of tides?
- Tides are used to generate powers.
- Tidal power stations are installed in UK, Canada, Japan, France.
- These are helpful in navigation Kumar trading and fishing.
- Water level near the coast rise during high tides.
- Due to this. Big ships and that and leave the harbour safely.
- Example: Diamond Harbour in West Bengal and Kandla in Gujarat.
- Huge silts are loaded at the mouth of the big river. Their deposits are washed by the tidal water resulting in opening of river mouth for ships and boots to enter and exits.
What are Ocean Currents?
- Ocean currents are streams of water flowing on the surface of ocean in definite direction.
- They are narrow, deep and swift.
- These ply at the speed of 2 -10 Km per hour
What are Drifts?
- Broad and slower currents that are shallow in depth or called Drifts.
- Drift ply at the speed of 1-3 kilometre per hour.
What are the reasons for the formation of Ocean currents?
- Ocean currents are formed due to planetary wins
- Difference in temperature of ocean water
- Shape of land masses
- Rotation of the Earth
- Difference in density of the ocean water.
Write the difference between Warm currents and Cold currents?
| Warm currents | Cold current |
| Warm current flow from equator to poles. | Cold current flow from polar areas towards the equator. |
| They are warmer than surrounding water. | They are colder than surrounding water |
How the ocean current move in both the hemispheres?
- Ocean current follow Ferrel’s law.
- They move clockwise in Northern hemisphere and anticlockwise in southern hemisphere.
What are the effects of ocean current?
- The temperature of the coast is raised by warm current and decreased by cold currents Winds that blow over the warm currents or moist and bring rainfall.
- Dry and cool wind blow over the cold current do not have any moisture.
- Ship sailing in the direction of the current move faster and saves time and fuel.
- When warm and cold currents meet, dense fog is created resulting in the little visibility and creating accidents.
- These area are called as Fishing banker. Example Dogger Bank, the Great Fisher Bank of North Sea.
Get some importance of ocean current?
- Ocean current play a major role in climatic changes.
- It helps to improve the economic life of people.
- It helps in creating the clouds and bring rainfall.
- Ocean transport. Cheapest transport in the world.
**********************************************************************************************************
Useful links