Very Short Answer Questions

Q1. What is the composition of the air?
Ans: Atmosphere is composed of various gases. Major gases present are:
(i) Nitrogen – 78%
(ii) Oxygen – 21%
(iii) Argon - .93%
(iv) Carbon Dioxide – 0.03%
Other Gases – 0.04% (like – helium, hydrogen, methane, ozone, etc. and water vapours & dust particles.

Q2. What is normal lapse rate?
Ans: Temperature decreases at the rate of 1 degree Celsius from every 165 mtrs of ascent. This decline is known as normal lapse rate.

Q3. Define: (a) Weather (b) Climate?
Ans:
(a) Weather: The condition of atmosphere at a particular place and time is known as weather.
(b) Climate: The sum total or average of the weather conditions of a large area over a longer period of time is known as climate.

Q4. What is dew point?
Ans: Temperature at which air gets saturated is known as "Dew Point".

Q5. Which layer of the atmosphere enables wireless communications?
Ans: Thermosphere or Ionosphere is the layer of the atmosphere enables wireless communications.

Q6. Name the unit used for measuring air pressure.
Ans: Barometer is the unit used for measuring air pressure.

 

Short Answer Questions

Q1. What are the factors affecting temperature of any place?
Ans. Following are the factors affecting temperature of any place:
(a) Latitude or Distance From Equator.
(b) Altitude or Height Above The Sea Level
(c) Distance From The Sea
(d) Prevailing Winds and Ocean Currents
(e) Slope of Land

Q2. Why is atmosphere important for us?
Ans. Importance of atmosphere and various gases present in it are:
(a) Life giving gases like oxygen for breathing of animal kingdom and carbon dioxide is inhaled by plant kingdom.
(b) Ozone layer protects us from harmful ultraviolet rays of the sun.
(c) Tiny dust particles help in the formation of the rain droplets.
(d) It acts as a blanket which prevents the earth from becoming too hot during day and too cold during night.
(e) It protects us from falling meteors and other cosmic dusts. They burn when coming in contact with the atmosphere.
(f) Presence of gases, dust particles and water vapours lend colours to sky.

Q3. What do you mean by precipitation? What is the main source of freshwater on the earth's surface?
Ans: The process in which water vapour falls on the surface of the earth is known as precipitation. Types of precipitation: Rainfall, Snowfall, Hail, Sleet, etc. Underground water is the main source of freshwater on the earth's surface.

Q4. What is atmospheric pressure? How is it important to us?
Ans: The weight of air on the earth's surface is referred to as "Atmospheric Pressure". Atmospheric Pressure is a very important element of weather and climate. A difference in the air pressure defines the direction of wind flow and accordingly, brings changes in the weather conditions.

Q5. What is the main cause of air pollution?
Ans: Any change in the composition of air is termed as "Air Pollution". Following are the main cause of air pollution:
(a) Rapid industrial growth.
(b) Excessive burning of the fossil fuels.
(c) Increase in numbers of automobiles.
(d) Burning of solid waste.
(e) Fire, etc.

Q6. Define: (a) Breeze (b) Drizzle
Ans:
(a) Breeze: These are local winds which blow only during a particular period of the day or year in a small area. For example, land and sea breeze.
(b) Drizzle: Light rainfall in the form of very tiny drop of water is called "Drizzle".

 

Long Answer Questions

Q1. Describe the structure of the atmosphere. Draw a diagram also.
Ans. Structure of Atmosphere: Atmosphere is divided into five different layers (Troposphere, Stratosphere, Mesosphere, Ionosphere and Exosphere). It extends upto 500 kms.

1. Troposphere:
• This layer is next to earth surface. It Extends upto 15 kms from the earth's surface.
• Temperature decreases at the rate of 1 degree Celsius from every 165 mtrs of ascent. This decline is known as normal lapse rate.
• Average height: 13 kms at poles and 18 kms over the equator.
• All weather changes take place in this layer. Oxygen exists in this layer.
• The boundary separating troposphere and stratosphere is known as tropopause.

2. Stratosphere:
• This layer is next to troposphere and it extends from 15 kms to 50 kms.
• This layer is free from weather changes, cloud formation and dust particles. Hence, this layer is ideal for the air transportation.
• Ozone layer is present here. Ozone layer absorbs/reflects the harmful ultraviolet rays of the sun.
• The boundary separating stratosphere and mesosphere is known as stratopause.

3. Mesosphere:
• This layer is next to stratosphere and it extends from 50 kms to 80 kms.
• Temperature again drops in this layer and can reach upto -100 degree Celsius at the upper boundary layer.
• The boundary separating mesosphere and ionosphere is known as mesopause.

4. Thermosphere:
• This layer is next to mesosphere and it extends from 80 kms to 400 kms.
• This layer contains electrically charged particles called ions, which are found at a height of 250 kms. Due to presence of these ions, this layer is also known as ionosphere.
• This layer protects us from the harmful radiation. Temperature increase with increase in height.

5. Exosphere:
• This is the uppermost layer above the ionosphere and it extends from 400 kms onwards and there is no end. It is a very thin layer and it merges with the space.
• This layer protects us from the harmful radiation.
• Temperature is very high. Light gases like hydrogen and helium float into space from here.

Q2. What are the different types of winds? Describe each giving examples.
Ans. Permanent or Planetary Winds: These winds blow constantly throughout the year in a particular direction. These winds are broadly classified as: -
(a) Trade Winds
(b) Westerlies
(c) Polar Easterlies

(a) Trade Winds: These winds blow from Sub-Tropical high pressure belt towards Equatorial low pressure belt. They blow from North-East in the northern hemisphere and South-East in the southern hemisphere.
(b) Westerlies: These winds blow from Sub-Tropical high pressure belt to Sub-Polar low pressure belt.
(c) Polar Easterlies: These winds blow from Polar high pressure belt to Sub-Polar low pressure belt.

2. Seasonal or Periodic Winds: These winds change their direction in different seasons. The best example is "Monsoon Winds".

3. Local Winds: These winds blow only during a particular period of the day or year. For example, land and sea breeze. These winds bring short time changes in the weather conditions over a smaller area. Some of the examples are: -
(a) Chinook: Chinook means 'snow eater'. These winds are strong, warm and dry. They blow in North America.
(b) Loo: These are hot and dry winds which, blow during the summer season in the northern part of India.
(c) Sirocco: These are hot and moist winds, which blow from Sahara desert to Mediterranean Sea.
(b) Mistral: These are very cold winds, which blow down from the Alps over France.

Q3. Describe the different types of rainfall, Support your answer with appropriate diagram.
Ans. Rainfall can be classified into three types:
1. Convectional Rainfall: When hot air expands and rise to the upper layer of the atmosphere, condensation takes place which leads to formation of clouds. These clouds produce sudden and heavy rainfall. It's a daily feature in the equatorial regions.

2. Relief Rainfall: Relief rain occurs when warm air is forced to cool when it rises over a hill or mountain and then condenses. The other name for relief rain is orographic rainfall. The windward side of the mountains receives heavier rainfall in comparison to that of the leeward side (opposite) of the mountain receives little or no rain at all. It always produces a rain shadow effect.

3. Cyclonic Rainfall: When warm air mass and cold air mass meet, the warm air being lighter climbs over the cold air and cools down, leading to formation of clouds and then rainfall. This type of rain usually is due to the occurrence of cyclonic activities.

Q4. Why do places lying the windward side get rainfall while the leeward side remains dry?
Ans: The windward side gets more rainfall than the leeward side of a mountain. This is because the prevailing winds come up and the cool air tries to hold that much moisture. But since cool air can't hold as much moisture as warm air, it begins to precipitate on the windward side (the side of mountain that is facing the prevailing winds). The dry air moves on to the leeward side (the side of a mountain that is not facing prevailing winds) and stays there, usually causing deserts to form. This makes the leeward side of the mountain have a dry climate.

 

Q5. What is a cyclone? How is it different from anti cyclone?
Ans. A cyclone is a large wind system that moves around an area of low atmospheric pressure. Surrounding air moves toward the low-pressure area and starts to circulate, cyclone moves clockwise in the Southern Hemisphere and anticlockwise in the Northern Hemisphere. Cyclones can produce cloudy weather and broad areas of rain and even snow. In the United States, cyclones often are called tornadoes.
An anticyclone system has characteristics opposite to that of a cyclone. That is, an anticyclone's central air pressure is higher than that of its surroundings, and the airflow is anticlockwise in the Southern Hemisphere and clockwise in the Northern Hemisphere.

 

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Some important points to remember:

• The gaseous envelope around the earth's surface consisting of mixture of gases, water vapour and tiny dust particles is called atmosphere.
• The atmosphere has its own weight called atmospheric pressure.
• Concentration of gases and other constituents of atmosphere decrease with the increase in height.
• Atmosphere is endless with no visible boundary.

 

COMPOSITION OF ATMOSPHERE:

Atmosphere is composed of various gases. Major gases present are:
(a) Nitrogen – 78%
(b) Oxygen – 21%
(c) Argon - .93%
(d) Carbon Dioxide – 0.03%
(e) Other Gases – 0.04% (like – helium, hydrogen, methane, ozone, etc. and water vapours & dust particles.

Importance of atmosphere and various gases present in it are:
(a) Life giving gases like oxygen for breathing of animal kingdom and carbon dioxide is inhaled by plant kingdom.
(b) Ozone layer protects us from harmful ultraviolet rays of the sun.
(c) Tiny dust particles help in the formation of the rain droplets.
(d) It acts as a blanket which prevents the earth from becoming too hot during day and too cold during night.
(e) It protects us from falling meteors and other cosmic dusts. They burn when coming in contact with the atmosphere.
(f) Presence of gases, dust particles and water vapours lend colours to sky.

 

STRUCTURE OF ATMOSPHERE:
Atmosphere is divided into five different layers (Troposphere, Stratosphere, Mesosphere, Ionosphere and Exosphere). It extends upto 500 kms.

1. Troposphere:

• This layer is next to earth surface.
• It Extends upto 15 kms from the earth's surface.
• Temperature decreases at the rate of 1 degree Celsius from every 165 mtrs of ascent. This decline is known as normal lapse rate.
• Average height: 13 kms at poles and 18 kms over the equator.
• All weather changes take place in this layer.
• Oxygen exists in this layer.
• The boundary separating troposphere and stratosphere is known as tropopause.

2. Stratosphere:

• This layer is next to troposphere and it extends from 15 kms to 50 kms.
• This layer is free from weather changes, cloud formation and dust particles. Hence, this layer is ideal for the air transportation.
• Ozone layer is present here. Ozone layer absorbs/reflects the harmful ultraviolet rays of the sun.
• The boundary separating stratosphere and mesosphere is known as stratopause.

3. Mesosphere:

• This layer is next to stratosphere and it extends from 50 kms to 80 kms.
• Temperature again drops in this layer and can reach upto -100 degree Celsius at the upper boundary layer.
• The boundary separating mesosphere and ionosphere is known as mesopause.

4. Thermosphere:

• This layer is next to mesosphere and it extends from 80 kms to 400 kms.
• This layer contains electrically charged particles called ions, which are found at a height of 250 kms. Due to presence of these ions, this layer is also known as ionosphere.
• This layer protects us from the harmful radiation.
• Temperature increase with increase in height.

5. Exosphere:

• This is the uppermost layer above the ionosphere and it extends from 400 kms onwards and there is no end.
• It is a very thin layer and it merges with the space.
• This layer protects us from the harmful radiation.
• Temperature is very high.
• Light gases like hydrogen and helium float into space from here.

 

GLOBAL WARMING:

• Earth's atmosphere acts as a green house with the presence of harmful gases coming out from the factories, vehicles, refrigerators, etc.
• There is a layer of carbon dioxide around the earth which does not allow the heat to radiate into the space, rather this layer blocks the heat, due to which there is increase in the temperature. This increase in temperature is known as global warming.
• When the temperature increases – snow melts – due to which the water level increases causing floods.
• There may be major changes in the climate leading to the extinction of some vegetation and wildlife.

WEATHER:
The condition of atmosphere at a particular place and time is known as weather.

METEOROLOGY:
The scientific study of weather is known as meteorology.

Temperature, pressure, wind, humidity, moisture, sunshine, precipitation, etc. are the major elements of weather and climate.

CLIMATE:

• The sum total or average of the weather conditions of a particular place over a longer period of time is known as climate.
• Climate influence the type of vegetation, agricultural crops grown, animals found, lifestyle, houses build, eating habits, etc.

INSTRUMENTS USED FOR MEASURING WEATHER:

1. Thermometer - Temperature
2. Barometer - Air Pressure
3. Rain Gauge - Rainfall
4. Wind Vane - Wind
& Anemometer

 

TEMPERATURE:

• The intensity of heat (warm or cold) is known as temperature.
• Main source of heat is sun.
• Surface temperature of sun is around 5500 degree Celsius.
• Heat energy given out by sun is known as solar radiation.
• Incoming solar radiation is known as insolation.
• The solar radiation takes 7 minutes to reach the earth's surface.
• Due to the spherical (round) shape of the earth, all parts does not receive same amount of insolation.
• On an around equator, insolation is maximum and it decrease when we move towards the poles.
• On the basis of the insolation received, earth is divided into different zones, which are as follows:-

          1. Torrid Zone
          2. Temperate Zone
          3. Frigid Zone 

 

Heating and Cooling of Atmosphere:
The heat energy given out by the earth is known as terrestrial radiation. It is the same heat which was absorbed by the earth through insolation.
Heat is transferred by the earth's surface into the atmosphere through the following ways: -
1. Conduction: The transfer of heat through contacts is known as conduction. In this, a cooler body comes in contact with the warmer body a gets heated up. This process is carried out until the temperature of both the bodies become same.

2. Convection: The actual movement of heat molecules from lower level to the higher level is known as convection. This process is common on equator and in tropics during the summers.

3. Advection: Transfer of heat from one place to another by the winds and the oceanic currents is known as advection. In this process, the cooler wind lowers the temperature of the warm wind and vice-versa, when they come in contact with each other.

4. Radiation: The process of releasing heat energy is known as radiation. The head energy absorbed by earth during the day time is radiated to the atmosphere during the night time.

 

Factors Affecting the Temperature:
Temperature is unequally distributed on the earth's surface and it differs from place to place. Factors controlling the temperature are as follows:

1. Latitude or distance from equator: Places located near the equator are warmer in comparison to the places located near the poles. Places near the equator receive direct sunrays because here the sunrays travel shorter distance and cover small area.
On contrary, in Polar Regions, sunrays travel longer distance and cover large area.

2. Altitude or height above the sea level: As we go higher the temperature decreases (i.e. 1 degree for every 165 metres). Mountainous areas are therefore cooler. The lower layers of atmosphere are denser and have water vapour and dust particles which absorb heat, which is not prevalent in the higher altitude. E.g. Missouri is cooler than Delhi.

3. Distance from the sea: The Sea is cooler than the land in summer, but warmer in winter. This is because it takes the sea a long time to heat up, but it is slower to cool down than land.
Areas experiencing uniform and mild temperature throughout the year as they are located near the sea have maritime type of climate. E.g. Mumbai.
Areas experiencing hot temperatures in summers and cold temperatures in winters due to longer distance from the sea have extreme or continental type of climate. E.g. Delhi.

4. Prevailing winds and ocean currents: Both winds and ocean currents (hot and cold) influence the temperature of the land. For e.g. hot and dry winds 'loo' in summers from Rajasthan increase the temperature of Delhi and in winters cold winds from Himachal Pradesh decreases the temperature of Delhi.

5. Slope of land: Slopes more exposed to sun, received more sunlight and these places are warmer. On contrary, slopes exposed less to sunlight are cooler and have less vegetation.

 

Temperature of a place is very important as it controls:

1. The presence or absence of water vapours or moisture.
2. Dryness or wetness of air and rainfall.
3. Type of crops to be grown.
4. Type of vegetation in an area.

 

ATMOSPHERIC PRESSURE:

• The weight of air on the earth's surface is referred to as "Atmospheric Pressure".
• Weight of dry air is about 1.2 ounce per cubic foot of air.
• Pressure decreases with increase in height. Pressure is highest at the sea level.
• The air always moves from high pressure to low pressure areas.
• Barometer is the instrument through which pressure variation can be measured.
• Pressure is measured in millibars. Average atmospheric pressure at sea level is 1013 millibars.

Factors responsible for difference in the Atmospheric Pressure:
1. Variations in Temperature Conditions.
2. Changing Altitude.

Distribution of Atmospheric Pressure:

High Temperature – Low Pressure
Low Temperature – High Pressure
The world is divided into seven different pressure belts:
1. Equatorial low pressure belt also called "Doldrums".
2. Subtropical high pressure belt from 30 to 35 degree in North.
3. Subtropical high pressure belt from 30 to 35 degree in South.
4. Sub Polar low pressure belt from 65 degree in North.
5. Sub Polar low pressure belt from 65 degree in South.
6. Polar high pressure belt in North Pole.
7. Polar high pressure belt in South Pole.

 

WIND:

• The movement of air from high pressure area to low pressure areas is called "Wind".
• Winds play a vital role as they are very important.
• Winds transports temperature and moisture from one place to another.
• Slope of pressure from high to low is known as "Pressure Gradient" and this decides the direction of the winds.
• Deflection of the winds is affected by the "Coriolis Force", which is caused by the rotation of the earth. Coriolis is absent on the equator and it increases towards the poles.

Types of Winds: Winds can be broadly divided into three types:
1. Permanent or Planetary Winds.
2. Seasonal or Periodic Winds.
3. Local Winds.

1. Permanent or Planetary Winds: These winds blow constantly throughout the year in a particular direction. These winds are broadly classified as: -
(a) Trade Winds
(b) Westerlies
(c) Polar Easterlies

(a) Trade Winds:

• These winds blow from Sub-Tropical high pressure belt towards Equatorial low pressure belt.
• They blow from North-East in the northern hemisphere and South-East in the southern hemisphere.

(b) Westerlies:

• These winds blow from Sub-Tropical high pressure belt to Sub-Polar low pressure belt.

(c) Polar Easterlies:

• These winds blow from Polar high pressure belt to Sub-Polar low pressure belt.

2. Seasonal or Periodic Winds: These winds change their direction in different seasons. The best example is "Monsoon Winds".
(a) Land Breeze: The offshore breeze is called "Land Breeze".
(b) Sea Breeze: The onshore breeze is called "Sea Breeze".

3. Local Winds: These winds blow only during a particular period of the day or year. These winds bring short time changes in the weather conditions over a smaller area. Some of the examples are: -
(a) Chinook: Chinook means 'snow eater'. These winds are strong, warm and dry. They blow in North America.
(b) Loo: These are hot and dry winds which, blow during the summer season in the northern part of India.
(c) Sirocco: These are hot and moist winds, which blow from Sahara desert to Mediterranean Sea.
(b) Mistral: These are very cold winds, which blow down from the Alps over France.

 

LOCAL STROMS:

• Stroms are very strong blowing winds and they are serious threat to life and property in the coastal areas.
• Cyclones, hurricanes, typhoons and tornadoes are some of the examples of stroms.

 

Cyclones:

• Cyclones refer to a violent and destructive form of winds followed by heavy rainfall.
• Cyclonic winds cause 7 to 10 km high tidal waves that sweep 20 kms inland and bring massive destruction.
• Hurricanes are type of cyclones, which are experienced by eastern coast of India.

Prevention:
These are the natural calamities which cannot be prevented but we can try to minimize the effect by the following ways:
1. People should live far away from the coastal lands.
2. Houses should be constructed with stronger building material.

Instruments:
1. Wind Vane is used to measure the direction of the wind.
2. Anemometer is used to measure the wind velocity.

 

CASE STUDY
CYCLONE IN ORISSA

On 29th of October 1999, a cyclone (hurricane) emerged from the Bay of Bengal. With winds up to 300 km/h and 30 feet tidal waves, it affected the state of Orissa for more than 36 hours. The impacts on people and the environment were massive because of poor preparation.

Effects:

• 20,000 people and 700,000 cattle died.
• 90 million trees have been uprooted or damaged.
• 20 million people were made homeless
• 5 million farmers are out of work
• 1.2 million hectares of standing cropland were destroyed.
• £1.5Billion damage

      

MOISTURE:

• Moisture content in air is called "Humidity".
• When the air is full of water vapour we call it a humid day. As the air gets warmer, its capacity to hold the water vapour increases and so it becomes more and more humid. On a humid day, clothes take longer to dry and sweat from our body does not evaporate easily, making us feel very uncomfortable.
• Instrument used to measure humidity is called "Hygrometer".
• Temperature at which air gets saturated is known as "Dew Point".
• When the water vapour rises, it starts cooling. The water vapour condenses causing formation of droplets of water. Huge masses of water droplets are known as "Clouds". When these droplets of water become too heavy to float in air, then they come down as precipitation.
• Types of precipitation: Rainfall, Snowfall, Hail, Sleet, etc. A very tiny drop of rain water is called "Drizzle".

 

TYPES OF RAINFALL:

Rainfall can be classified into three types:

1. Convectional Rainfall: Sudden and heavy rainfall
2. Relief Rainfall: The windward side of the mountains receives heavier rainfall in comparison to that of the other side.
3. Cyclonic Rainfall: Rainfall is associated with cyclones.

 

POLLUTION:

• Any change in the composition of air is termed as "Air Pollution".
• Some of the air pollutants are: Chlorofluorocarbons (CFC), Carbon Dioxide, Carbon Monoxide, Shulphur Dioxide, Nitrogen Oxide, etc.
• Some of the hazards of air pollutions are: Health problems, Loss of biodiversity, Damage to the historical monuments (e.g. Taj Mahal is getting harmed), etc.
• Serious steps should be taken to protect the environment and the human life.

 

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Multiple choice questions:

Q1. .............. environment consists of plants, animals and human beings. (1)
(a) Abiotic (b) Chemical (c) Human (d) Biotic

Ans: (d) Biotic

Q2. "NIFE" is related to which layer of the earth? (1)
(a) Core (b) Mantle (c) Crust (d) Mountains

Ans: (a) Core

 

Very short answer questions:

Q3. Study of relationship between living organisms and their surrounding is called? (1)
Ans: Study of relationship between living organisms and their surrounding is called Ecology.

Q4. Fossil fuels are found in which type of rocks? (1)
Ans: Fossil fuels are found in Sedimentary rocks.

Q5. What is oceanic crust called? (1)
Ans: The ocean crust is called SIMA.

 

Short answer questions:

Q6. What is lithosphere? Why it is important? (2)
Ans: The hard outermost solid layer of the earth which is made up of rock material is called crust. This solid crust of the earth is called Lithosphere. On this lithosphere we find different landforms such as the mountains, plateaus and plains. It provides us land where we live and also, it is a great source of vegetation, wildlife and mineral wealth. The crust is covered by a thin layer of soil which is of great importance for life. Lithosphere provides us the three basic necessities of life, i.e. Food, Cloth and Shelter.

Q7. Distinguish between: Crust and Mantle. (2)
Ans:

Q8. Define the terms: (a) Focus (b) Epicenter (2)
Ans:
(a) Focus: The point of origin of an earthquake is called its Focus.
(b) Epicenter The point directly/vertically above the focus on the earth's surface is known as Epicenter.

 

Medium answer questions:

Q9. What is igneous rock? Write its main features. (3)
Ans: The word 'Igneous' is derived from Latin word "Ignis" meaning "Fire". This is also called Primary rock. These are the first rocks to be formed and are known as the ancestors of all the rocks. Igneous rocks are the hardest rocks available and it is formed by cooling and solidification of the Lava coming out from the interior of the Earth's interior. E.g. Granite, Basalt, etc. Igneous rocks are of two types:
(a) Solidification of rocks below the earth's surface is known "Intrusive rocks".
(b) The magma which reaches the earth's surface and gets solidified is known as "Extrusive Rocks".

Features of igneous rocks are:
1. These rocks do not form layers.
2. They contain crystals of varying sizes.
3. They do not contain fossils.

Q10. Describe the rock cycle with a suitable diagram. (3)
Ans: Rocks undergo a cycle of transformation. Change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Hence, this cycle of change from one type of rock to another is called 'rock cycle'.

Rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

Q11. Explain the types of volcanoes? (3)
Ans: Natural openings in the earth's crust through which molten materials, rocks, ashes, gases, etc are thrown out are called 'Volcanoes'. Volcanoes are classified into three types:
(a) Active Volcanoes: These volcanoes erupt frequently and give out gases, ash, lava, etc. e.g. Mt. Etna in Italy.
(b) Dormant Volcanoes: These are also known as 'Sleeping Volcanoes'. They erupt after a very long time. E.g. Mt. Vesuvius in Italy.
(c) Extinct Volcanoes: These are also known as 'Dead Volcanoes'. They have been inactive since a very long time. E.g. Mt. Kilimanjaro in East Africa.
Long answer questions:

Q12. With a suitable diagram write a note on the domains of the earth. (5)
Ans:
Lithosphere: The solid crust of the earth is called Lithosphere.
Hydrosphere: The water bodies on the earth's surface together form the Hydrosphere.
Atmosphere: The layer of air around us is called Atmosphere.
Biosphere: The living world where land, water & air interact with each other to support life is called the Biosphere.
Plant and animal kingdom together make Biosphere or the living worlds. It is a narrow zone of the Earth where Air (Atmosphere), Water (Hydrosphere) and Land (Lithosphere) interact with each other to support life. All the three spheres are equally important for the existence of life or the Biosphere.

Q13. Explain the following. (5)
(a) Aggradation (b) Endogenis forces (c) Tectonic plates (d) Delta (e) Meanders
Ans:
(a) Aggradation: The process of depositing the eroded material is called aggradation.
(b) Endogenic Forces: Forces which are working in the interior of the earth leading to earth movements, earthquakes and volcanic eruption are known as endogenic forces.
(c) Tectonic Plates: The crust of the earth is broken into a number of large and small plates known as the Tectonic Plates or the Lithospheric plates.
(d) Delta: The network of distributaries forming a triangular shaped feature on the river mouth is known as delta.
(e) Meanders: Curves and large bends or loops formed by rivers in the plains are known as meanders.

 

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Objectives and Goals:

• Pangaea.
• The Continental Drift Theory.
• The Theory of Plate Tectonics.
• The forces active behind the changes on the earth.
• The Lithospheric Plates.
• The Tectonic Movements.
• Endogenic (Internal) and Exogenic (External) Forces.
• The Earth Movements.
• The Volcanoes.
• Three different types of volcanoes (i.e. Active, Dormant and Extinct).
• Earthquakes. Instrument used to measure an earthquake.
• The major landforms. Weathering, Erosion, Aggradations and Degradation.
• Work of a river and features formed by a river.
• Work of ice and features formed by ice.
• Work of wind and features formed by wind.
• Work of waves and features formed by waves.

 

Some important points to remember: -

• Forces like earthquake and volcanoes occurs beneath the earth's crust.
• Forces like weathering, erosion, etc. are responsible for the changes on the earth's surface.
• Forces are of two types: Endogenic (Internal) and Exogenic (External) forces.

(a)    Endogenic (Internal) Forces: Forces which form mountains, plateaus, plains, rising & sinking of coastal plains, movement of continental blocks, etc. These are slow and sudden forces. Internal forces are: -

         (i)   Earth Movements

         (ii)  Earthquakes

         (iii) Volcanoes

(b)   Exogenic (External) Forces: These forces originate on earth and form new landforms on the earth's surface. External forces such as: -

          (i)   Changes in atmospheric conditions.

          (ii)  Rivers, glaciers, sea waves and winds.

 

Earth Movements:

 Earth's crust or lithosphere consists of several lithospheric plates.Surface of Earth changes as the lithospheric plates moves.Earth movements arise inside the earth.Temperature and pressure inside the earth changes causes changes on the earth's surface.

According to the theory of continental drift, the world was made up of a single continent through most of geologic time. That continent eventually separated and drifted apart, forming into the seven continents we have today. The first comprehensive theory of continental drift was suggested by the German meteorologist Alfred Wegener in 1912.

Million of year also there was a single continent named "Pangaea". Pangaea broke into pieces due to internal forces and is drifting away from each other since last almost 250 million years.Two landmasses – "Laurasia in North" and "Gondwanaland in South". Both the landmasses were separated by a shallow sea called "Tethys Sea".Size of Tethys Sea kept on decreasing due to movement of landmasses towards each other, thus, resulting in the formation of the young fold mountains "Himalayas".

 

 

Theory of Plate Tectonics:

The continental blocks or the plates are floating on mantle. They move with the change or release of pressure and temperature inside the earth.Tectonic movements are of two types:

(a)    Vertical Movement: Causes land to uplift or subside or both.

(b)   Horizontal Movement:  Formation of mountains, trenches in the sea, widening of water bodies, etc. Such movements can cause both folding and faulting of structure.

 

Folding:

Caused by compression, when blocks of landforms come closer to each other, they form wrinkles or folds on the earth's surface. E.g. the young fold mountains 'Himalayas'. These young fold mountains are formed by sedimentary rocks.

Faulting:

The structure of rocks cracks or breaks along the weaker areas due to tension, this is called faulting. This may cause upliftment and subsidence of land and can form Block Mountains. E.g. Vindhyas and Satpura hills.When a part of land subsides between two faults, it forms Rift Valley. Narmada & Tapti Rivers flow through the rift valley.

 

Earthquakes:

• The crust of the earth has cracks in it called the 'Faults'.
• The study of earthquake shocks and its effects is called 'Seismology'.
• Instruments used to records the shaking of land is known as 'Seismograph'.
• The vibrations are called Seismic Waves.Earthquake is measured from 1 to 10 on the Richter Scale.
• The point of origin of an earthquake is called its 'Focus'.
• The point directly/vertically above the focus on the earth's surface is known as 'Epicenter'.
• The scientists who study earthquake is known as 'Seismologists'.

 

Effects of earthquakes:

• Displacement of the earth's crust (uplifts and subsides).
• Results in landslides and avalanches in mountainous regions.
• Destruction done by earthquakes can be seen like, falling of buildings, damaged roads, communication system, etc.

 

Volcanoes:

• Natural openings in the earth's crust through which molten materials, rocks, ashes, gases, etc are thrown out are called 'Volcanoes'.
• Volcanoes erupt due to excessive 'heat and pressure' inside the earth.
• The opening through which lava comes out is called 'Vent of Volcano'.
• The funnel shaped depression at the top of the vent is called 'Crater'.
• Around the Pacific Ocean along the belt of volcanoes called 'Ring of Fire'.
• About 68% of volcanoes occur in this region.
• Lava ejected by volcanoes can be thick or thin in nature.

 

Volcanoes are classified into three types: -

(a)    Active Volcanoes: These volcanoes erupt frequently and give out gases, ash, lava, etc. e.g. Around Pacific Ocean, Hawaii Islands, etc.

(b)    Dormant Volcanoes: These are also known as 'Sleeping Volcanoes'. They erupt after a very long time. E.g. Mt. Vesuvius in Italy.

(c)    Extinct Volcanoes: These are also known as 'Dead Volcanoes'. They have been inactive since a very long time. E.g. Mt. Kilimanjaro in East Africa.

 

MAJOR LAND FORMS

• The landscape is being continuously changing away by two processes – weathering and erosion.
• Weathering is the breaking up of the rocks on the earth's surface.
• Erosion is the wearing away of the landscape by different agents like water, wind and ice.
• The eroded material is carried away or transported by water, wind, etc. and eventually deposited.
• This process of erosion and deposition create different landforms on the surface of the earth.
• The process of reduction of height of landform is called 'degradation'.
• The process of depositing the eroded material is called 'aggradation'.

 

Work of a River:

1.  Rivers are the most important agents of degradation.

2.  Work of the river depends on two factors: -

(a)  The volume of Water.                                     (b)  Slope of river beds.

3.  Common features formed by river while flowing through mountains: -

(a)  'I', 'V' shaped valley.                             (b) Gorges or Canyons (deep valleys)

(c)  Waterfalls, etc.

4.   Common features formed by river while flowing through plains: -

(a)  Meanders (curves & large bends or loops)      (b) Oxbow Lakes

(c)  Flood Plains                                                    (e)  Levees (slightly raised river banks)

5.   Common features formed by river when it reaches near the sea: -

(a)  River breakup into various streams called 'distributaries'.

(b)  Delta

 

Work of Sea Waves

• The erosion and deposition of the sea waves gives rise to coastal landforms.
• Sea waves continuously strike at the rocks. Cracks develop. Over time they become larger and wider. Thus, hollow like caves are formed on the rocks. They are called sea caves.
• When these cavities become bigger and bigger only the roof of the caves remain, thus forming sea arches.
• Further, erosion breaks the roof and only walls are left. These wall like features are called stacks.
• The steep rocky coast rising almost vertically above sea water is called sea cliff.
• The sea waves deposit sediments along the shores forming beaches.

 

Work of Ice

• Glaciers are "rivers" of ice which too erode the landscape by bulldozing soil and stones to expose the solid rock below.
• Glaciers carve out deep hollows. As the ice melts they get filled up with water and become beautiful lakes in the mountains.
• Formation of "U" shaped valleys, which are deep and have steep sides.
• The material carried by the glacier such as rocks big and small, sand and silt gets deposited. These deposits form glacial moraines.

 

Work of Wind

• An active agent of erosion and deposition in the deserts is wind.
• In deserts you can see rocks in the shape of a mushroom, commonly called mushroom rocks.
• Winds erode the lower section of the rock more than the upper part. Therefore, such rocks have narrower base and wider top.
• When the wind blows, it lifts and transports sand from one place to another.  When it stops blowing the sand falls and gets deposited in low hill – like structures. These are called sand dunes.
• When the grains of sand are very fine and light, the wind can carry it over very long distances.
• When such sand is deposited in large areas, it is called loess. A large deposit of loess is found in China.

 

 

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Objectives and Goals:

• The interior of the earth.
• The three different layer of the earth (i.e. Crust, Mantle and Core).
• Differences between rocks and minerals.
• The classification and characteristics of rocks (i.e. Igneous, Metamorphic and Sedimentary Rocks).
• The "Rock Cycle".
• The usefulness of rocks.

 

Some important points to remember:

• Lithosphere (outer part of earth's structure) was formed 5 billion years ago. 
• Geologists are the scientists who study the earth, its structure and substances. 
• Petrology is the science which studies rocks and its formations. 
• Fossils – remains of dead plants and animals are called fossils trapped in the layers of rocks. 
• Ore – a rock in which a particular mineral is found in large percentage is called an ore. 
• Plates – large blocks of earth's crust which are moving. 
• Magma – it is molten rock material inside the earth. 
• Rock cycle – rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

 

The radius of Earth is 6371 kms.  Earth's interior is broadly divided into three layers: -

1. Crust – Forms only 0.5% of the total Earth's volume.

2. Mantle - Forms only 16% of the total Earth's volume.

3. Core - Forms only 83% of the total Earth's volume.

 

CRUST:

• Its is also called SIAL (Silica & Aluminum)
• The outermost and thinnest layer of Earth.
• It consists of lightest materials and its density is lowest.
• Average thickness varies from 5 to 8 kms under the ocean floors and 35 kms under the continental masses.
• Broken in large continental blocks called "Plates".
• Lower part of Crust (oceanic crust) is known as SIMA (Silica & Magnesium).

 

MANTLE:

• Layer located under the Crust is called "Mantle".
• Its thickness is about 2900 kms.
• This layer is in partially molted form.
• Lithosphere plates (Crust) floats on this layer.
• Layer is divided into two – Upper and Lower Mantle. The upper mantle is in solid form, whereas lower mantle is in semi-molten form.
• Average temperature: Upper Mantle – 870 degree Celsius and Lower Mantle – 2200 degree Celsius.
• This layer is made up of Iron, Magnesium and Silica.

 

CORE:

• The innermost layer, forming the metallic centre of the Earth.
• Core of the Earth is like a dense magnetic ball of minerals (Iron & Nickel). Hence, it is also called NIFE (NI – Nickel & Fe – Ferrous Magnesium i.e Iron).
• Temperature increases at the rate of 1degree Celsius for every 32 meters of depth.
• This layer is divided into two:

            (a) Outer Core: It is so hot that even metal also melts. Temperature is around 2200 degree Celsius.

            (b) Inner Core: Here the temperature is around 5000 degree Celsius.  Pressure is maximum in this layer.

 

MATERIAL OF THE EARTH'S CRUST

Earth's crust is composed of rocks and minerals. All solid materials of the earth's crust, whether hard or soft, that make up the earth's crust are called Rocks.

 

Characteristics of Rocks:

• They are made up of one or more minerals.They don't have a definite chemical composition.There are broadly 12 rocks forming minerals.
• Rocks form the solid mass of the earth's crust.
• The rock forming materials are known as "Minerals".
• Minerals are chemical substances found in nature. They have definite chemical composition and physical characteristics. Any variation in their proportion gives rise to a different mineral.
• Rocks containing minerals gives us metals like Copper, Iron, Gold, etc.

 

Rocks have different colours, mineral composition, hardness, etc. and according to their formation, rocks can be classified into three categories: -

1.  Igneous Rocks

2.  Sedimentary Rocks

3.  Metamorphic Rocks

 

1.  IGNEOUS ROCKS

The word 'Igneous' is derived from Latin word "Ignis" meaning "Fire".

• This is also called Primary rock. These are the first rocks to be formed. These are ancestors of all the rocks.
• Igneous rocks are the hardest rocks available and  it is formed by cooling and solidification of the Lava coming out from the interior of the Earth's interior. E.g. Granite, Basalt, etc.
• Solidification of rocks below the earth's surface is known "Intrusive rocks".
• The magma which reaches the earth's surface and gets solidified is known as "Extrusive Rocks".

Features of igneous rocks are: -

• These rocks do not form layers.
• They contain crystals of varying sizes.
• They do not contain fossils.

 

2.  SEDIMENTRY ROCKS

• The word 'Sedimentary' is derived from Latin word "Sedimentum" meaning "Settle Down".
• Particles that form a sedimentary rock by accumulating are called sediments.
• Before being deposited, sediment was formed by weathering and erosion in a source area, and then transported to the place of deposition by water, wind, ice, mass movement or glaciers which are called agents of denudation.

Features of igneous rocks are: -

• They are layered, called stratified rocks.
• They do not contains crystals.
• They contain fossils embedded in them.
• They are rich in coal and petroleum deposits.
• Examples of Sedimentary rocks are: - Sandstone, Clay, Limestone, etc.
• 70% of the total earth's surface is dominated with these rocks.

 

3.  METAMORPHIC ROCKS

• The word 'Metamorphic' is derived from Greek word "Metamorphose" meaning "Change of Form".
• When igneous or sedimentary rocks are subjected to great heat or pressure, the original character and appearance of the rock change into a new form. Thus, these rocks are formed by the alteration of other rocks. E.g. graphite, slate, Marble, etc.

Features of metamorphic rocks are: -

• They are hard in nature.
• Valuable minerals like gold & silver are found in these rocks.
• They do not contain fossils.
• Takes a long time to form.

 

ROCK CYCLE

Change into sedimentary rock or into metamorphic rock. Sedimentary rock can change into metamorphic rock or into igneous rock. Metamorphic rock can change into igneous or sedimentary rock. Hence, this cycle of change from one type of rock to another is called 'rock cycle'.

Rock Cycle: Rocks are continually being formed, destroyed and reformed due to changing weather conditions and forces of nature (eg. Wind, river, glaciers, earth movements, etc.)

             

 

ROCKS PROVIDE US:

• Different vegetations.
• Different types of minerals for industries.
• Different rock materials for construction purposes.
• Different chemicals for medicine and fertilizer industries.
• Source of fuels like coal and crude oil.Source of precious stones like, gold, silver, etc.

 

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Project Topic                           :      OUR ENVIRONMENT

Software Used                         :       MS POWERPOINT

 

Important: Project should be prepared only on the basis of the educational field trip which was organized on 27 April 2014 (Sunday).

 

GUIDELINES (SOCIAL SCIENCE - GEOGRAPHY):

1.   Students will highlight all the details related to the environment which they have seen, noticed, observed, felt during the educational field trip organized on 27 Apr 2014.

2.   Student needs to explain role of human beings in the construction or destruction of the environment.

3.   Add photographs to your presentation to highlight the important phases of the trip.

 

GUIDELINES (ENGLISH):

1.   Presentation, delivering and briefing the topic as per the slides.

2.   Uses of language and Sentence Formation.

3.   Overall content.

 

GUIDELINES (COMPUTER SCIENCE):

1.   Students will prepare a documentation of minimum of 15 slides.

2.   Document must be formatted using various formatting options.

3.   Animation effects should be given to all the slides.

4.  Proper clip art, word art and all formatting should be done.

5.  Use of Auto shapes i.e., Banners, Call outs, etc. should be made to make to make presentation attractive.

6.  Rehearse Timings should be given to the presentation.

7.  You can also give Sound (Audio) and Video files to your presentation.

8.  Flow charts can be projected to explain sequence if needed.

9.  The Presentation should be typed using proper Case as needed and should summarize the entire plan of trip.

 

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