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Class 7 Social Science Chapter 5 Our Earth Notes Questions and Answers
Our Earth Class 7 Notes Pdf
Class 7 Social Science Chapter 5 Question Answer Kerala Syllabus
Question 1.
Observe the picture given below. What information do you get about the interior of the Earth?
Answer:
- The interior of the earth is divided into different layers.
- The outermost layer is the Crust.
- Mantle is the layer below the Crust.
- The inner layer is the Core. It is divided into the Inner core and outer core.
Question 2.
Prepare a note on the interior of the earth.
Ans:
Crust
The crust is the outermost and relatively thin layer of the earth. This layer is made up of solid rocks. The crust has two parts, namely continental crust and oceanic crust. The continental crust is thicker than the oceanic crust. The average thickness is about 30 kilometres. In mountain areas. continental crust has a thickness of about 70 kilometres, but the average thickness of the oceanic crust is 5 kilometres.
Mantle
The mantle is the layer below the crust. This is relatively thick. It extends up to about 2900 kilometres. The part of the earth that comprises the crust and the upper part of the mantle is called the lithosphere. The part a molten state due to the melting of rock particles (magma), is known as the asthenosphere. The portion below the asthenosphere is in solid state.
Core
The layer below the mantle is the core. It is divided into an outer core and an inner core. The outer core is in liquid state, while. the inner core is in solid state. The core is mainly made up of metals like Nickel (Ni) and Iron (Fe). Hence, the core is also known as NIFE. The temperature in the inner core is about 5500 degrees Celsius.
Question 3.
Complete the diagram given below by including the features of each layer of the earth’s interior.
Structure of the Earth – Features
Answer:
Crust
- Thin Layer
- It has two parts, namely Continental Crust and Oceanic Crust.
Mantle
- Thick layer
- The part of the earth that comprises the crust and the upper part of the mantle is called the lithosphere.
Core
- The layer below the mantle
- Divide into Outer Core and Inner Core
Question 4.
The features of each layer of the Earth’s interior are given in the table. Draw ‘
‘towards the correct ones and ‘
‘towards the wrong ones.
| The crust is the outermost solid part of the earth, which is made up of rocks. |
| Lithosphere is made up of crust and upper mantle. |
| The asthenosphere is the molten part formed by the molten rock particles (magma) |
| The outer core is in liquid state |
| The continental crust and the oceanic crust are the two parts of the crust. |
| The core is also known as NIFE |
Answer:
Question 5.
Illustrate the structure of the earth in a chart by giving separate colour for each layer. Write the features and display it in the class.
Answer:
Crust
- Outermost and relatively thin layer of the earth.
- The crust has two parts, namely continental crust and oceanic crust.
- The average thickness of the Continental Crust is about 30 km, and the Oceanic crust is 5 km.
Mantle
- Mantle is the layer below the crust.
- It extends up to about 2900 kilometres.
- The part of the earth that comprises the crust and upper part of the mantle is called the lithosphere.
- which is in a molten state due to the melting of rock particles (magma) is known as asthenosphere.
Core
- Below the mantle is the core
- It is divided into an outer core (liquid state) and an inner core(solid state).
- The core is also known as NIFE.
- The temperature in the inner core is about 5500 degrees Celsius.
Question 6.
With the title “The Interior Features of the Earth’ prepare notes by including additional information.
Answer:
Understanding the interior features of the Earth helps us learn about its structure and the processes that shape our planet. The Earth is made up of different layers, each with unique characteristics. These layers include the crust, mantle, and core.
Layers of the Earth
The Earth is divided into three main layers: the crust, the mantle, and the core. Each layer has distinct properties and compositions.
a) The Crust
Characteristics:
- The outermost layer of the Earth.
- Solid and relatively thin compared to other layers.
- Made up of rocks like granite and basalt.
Types:
- Continental Crust: Thicker (about 30-50 km) and less dense, composed mainly of granitic rocks.
- Oceanic Crust: Thinner (about 5-10 km) and more dense, composed mainly of basaltic rocks.
- Temperature: Varies from the surface temperature to about 400°C near the bottom.
- Fun Fact: The deepest mine in the world, the Mponeng Gold Mine in South Africa, is about 12 km deep, but this is still just a tiny fraction of the way through the crust!
b) The Mantle
Characteristics:
- Located beneath the crust and extends to a depth of about 2,900 km.
- Semi-solid (viscous) and capable of flowing very slowly.
- Composed mainly of silicate minerals rich in iron and magnesium.
Sub layers:
- Upper Mantle: Includes the lithosphere (rigid outer part) and the asthenosphere (more plastic and can flow).
- Lower Mantle: More rigid due to higher pressure but still able to flow very slowly.
Temperature: Ranges from about 400°C to 4,000°C.
Fun Fact: The mantle is responsible for plate tectonics, which causes earthquakes and volcanic eruptions.
c) The Core
Characteristics:
The innermost layer of the Earth, divided into the outer core and the inner core.
Composed mainly of iron and nickel.
Sub layers:
- Outer Core: Liquid, extending from 2,900 km to 5,150 km deep. It generates the Earth’s magnetic field.
- Inner Core: Solid, extending from 5,150 km to the Earth’s centre at 6,371 km. Extremely dense and hot.
- Temperature: Can reach up to about 5,500°C at the centre.
- Fun Fact: The movement of the liquid outer core creates Earth’s magnetic field, which protects us from harmful solar radiation.
Question 7.
Apart from Oxygen and Carbon dioxide what are the other gases present in the atmosphere? Observe the picture given below and answer the following questions.
i) Which is the most abundant gas present in the atmosphere?
ii) What is the combined percentage of Nitrogen and Oxygen to the total atmospheric composition?
Answer:
Nitrogen
Argon
Neon
Helium
Krypton
Xenon
Hydrogen
i. Nitrogen
ii. 99%
Question 8.
How Dust Particles reach the atmosphere?
Answer:
- Lifted from the earth by wind
- Coming out during volcanic eruptions
- Ash produced during burning of meteors
- Through Transportation
Question 9.
How atmosphere helps in the survival of life on earth?
Answer:
- Causes atmospheric phenomena
- Protects from harmful sun rays
- It acts as a Blanket of Earth.
Question 10.
Write down how each of the following factors helps to sustain life on the earth?
Answer:
| Atmospheric air | Respiration and Photosynthesis Maintaining Temperature and Climate Protecting from Harmful Solar Rays Supporting the Water Cycle Enabling Human Activities (Breathing, Energy Generation etc) |
| Water Particles in the Atmosphere | Water Cycle Temperature Regulation Supporting Plant Life Rain Ecosystem Support |
| Dust Particles in the atmosphere | Human Health and Agriculture Protection from Solar Rays Influence on Climate and Weather |
Question 11.
Observe the following pictures. What activities cause atmospheric pollution?
Answer:
- Smoke from Factories
- Vehicle Emission
- Burning of Plastic
- Stubble Burning
- Bursting of Fire cracks
- Volcanic eruption
Question 12.
What causes an increase in the level of atmospheric pollution in industrial cities?
Answer:
- Overuse of Vehicles
- Excessive use of CFC (Refrigerator, Air conditioners etc)
- Increase of Population
- Excessive Use of Fossil Fuels
- Deforestation
Question 13.
What can we do to reduce atmospheric pollution? Observe the pictures given below. Write down your findings and present in the class.
Answer:
- Afforestation
- Using of Solar energy
- Using Bicycles
- Promote the adoption of Electric and hybrid vehicles
- Urban Planning and Green Spaces
Question 14.
Observe the diagram given below and list the layers of the atmosphere
Answer:
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Question 15.
Why the troposphere is called the most important layer of the atmosphere?
Answer:
Because Atmospheric phenomena such as cloud formation, rain, snow, wind etc. occur in this layer
Question 16.
Why do the high-altitude regions like Ooty, Munnar, Kodaikanal, etc., feel cold?
Answer:
Because Temperature decreases with an increase in height.
Question 17.
What activities can be done in class and school on Ozone Day? Discuss.
Answer:
- Educational Presentations and Workshops
- Classroom Discussions and Debates
- Art and Poster Competitions
- Film Screenings
- Interactive Activities and Experiments
- Outdoor Activities and Clean-up Campaigns
- Awareness Campaigns and Pledges
- Collaborative Projects
Question 18.
Prepare identity cards as in the model given below by including the characteristics of the earth’s atmosphere.
Answer:
Troposphere
- Average height of 13 km from the earth’s Surface
- The temperature of the atmosphere decreases
- Atmospheric phenomena such as cloud formation, rain. snow, wind etc occurs in this layer.
Stratosphere
- Average height is about 50 km from the earth’s surface
- The temperature decreases
- Ozone layer is in the Stratosphere.
Mesosphere
- It extends from about 50 km to 80 km above the stratosphere
- Decrease in temperature with the increase in height
- Meteors that enter the Earth’s atmosphere burn down.
Thermosphere
- It lies about 80 to 400 km
- The temperature increases with an increase in altitude.
- The lower part of the thermosphere is called the Ionosphere
Exosphere
- It lies above 400 km
- The temperature increases with altitude
- Air molecules gradually reduce and dissolve into space
Question 19.
The atmospheric layers and their features are given below. Match them correctly.
Answer:
| Exosphere | Air molecules gradually reduce and dissolve into space |
| Thermosphere | Temperature increases with increase in altitude |
| Mesosphere | The layer with the lowest temperature The layer where meteors burn to ash |
| Stratosphere | Zone where ozone is present |
| Troposphere | The layer in which temperature decreases at a certain rate according to the increase in height Located at an altitude of 80 to 400 kilometre |
Extended Activities
Question 1.
Prepare a model of the earth’s structure and display it in the Social Science lab.
Answer:
(Hints)
Materials Needed:
- Large Styrofoam ball (representing Earth)
- Paints (blue, green, brown, red, yellow)
- Brushes
- Craft knife or Styrofoam cutter
- Labels or small flags
- Toothpicks or small sticks
- Glue
- Cardboard or foam board (for the base)
- Marker
Step 1: Prepare the Styrofoam Ball
Select a Ball: Choose a Styrofoam ball of an appropriate size (e.g., 20-30 cm in diameter) to represent the Earth.
Cut the Ball: Carefully cut the ball in half using a craft knife or Styrofoam cutter. One half will show the Earth’s surface, and the other half will display the internal layers.
Step 2: Paint the Earth’s Surface
Paint the Surface: On one half of the Styrofoam ball, paint the Earth’s surface. Use blue for oceans, green for forests, and brown for mountains and deserts. This half will show the Earth’s exterior.
Details: Add details like continents and major landforms to make it more realistic.
Step 3: Paint the Interior Layers
Base Color: Paint the other half of the ball with a base colour (e.g., a light colour like white or grey).
Layer Representation:
Crust: Paint a thin outer layer brown or dark grey (1-2 cm thick).
Mantle: Paint the next layer (up to about halfway to the centre) in shades of red, orange, or yellow to represent the mantle. Outer Core: Paint the next section yellow or light orange to represent the liquid outer core.
Inner Core: Paint the central sphere red to represent the solid inner core.
Step 4: Label the Layers
Create Labels: Make small labels for each layer: Crust, Mantle, Outer Core, Inner Core.
Attach Labels: Attach the labels to toothpicks or small sticks. Insert the toothpicks into the appropriate sections of the painted half of the Styrofoam ball.
Step 5: Prepare the Base
Cut the Base: Cut a piece of cardboard or foam board large enough to hold the two halves of the Styrofoam ball.
Mount the Halves: Glue the two halves onto the base. The surface-painted half should be placed upright, while the interior half can be placed next to it, showing the cross-section.
Question 2.
With the help of internet, prepare slides and explain the structure and features of the Earth.
Answer:
(Hints)
Slide 1: Title Slide
Title: The Interior Features of the Earth Subtitle: Understanding the Layers of Our Planet
Image: A cross-section of the Earth
Slide 2: Introduction
Title: Introduction
Content:
- Brief overview of the Earth’s structure
- Importance of studying the Earth’s interior
Image: Earth from space
Slide 3: The Earth’s Layers
Title: The Earth’s Layers
Content: The Earth is divided into three main layers: the crust, mantle, and core.
Image: Diagram showing the Earth’s layers
Slide 4: The Crust
Title: The Crust
Content:
- The outermost layer
- Thickness varies (5-70 km)
- Composed of continental and oceanic crust
Image: Close-up of the Earth’s crust, showing rocks and soil
Slide 5: The Mantle
Title: The Mantle
Content:
Located below the crust
Extends to a depth of 2,900 km
Semi-solid, with a flowing asthenosphere
Image: Diagram showing the upper and lower mantle.
Slide 6: The Core
Title: The Core
Content:
- Divided into outer core and inner core
- Outer core: liquid, generates magnetic field
- Inner core: solid, composed of iron and nickel
Image: Cross-section showing the core layers
Slide 7: How We Know About the Earth’s Interior
Title: How We Know About the Earth’s Interior
Content:
- Volcanic eruptions.
- Mining and drilling
- Seismic waves
Image: Seismograph and a volcanic eruption
Slide 8: Conclusion
Question 3.
Prepare an essay on atmospheric structure and its features and present it in the class.
Answer:
Introduction
The atmosphere is a protective shield composed of several layers, each with distinct characteristics. It extends from the Earth’s surface to the edge of space and is vital for life as it provides oxygen, protects from harmful solar radiation, and helps regulate temperature.
The Layers of the Atmosphere
The atmosphere is divided into five main layers based on temperature variations: the troposphere, stratosphere, mesosphere, thermosphere, and exosphere. Each layer has unique properties and functions.
The Troposphere Characteristics:
Altitude: Extends from the Earth’s surface up to about 8-15 kilometres (5-9 miles).
Temperature: Decreases with altitude, ranging from about 15°C (59°F) at the surface to -60°C (-76°F) at the top.
Composition: Contains roughly 75% of the atmosphere’s mass, including water vapor, oxygen, nitrogen, and other gases.
Features: Weather and climate phenomena occur in this layer, including clouds, rain, and storms.
Importance:
The troposphere is where we live and breathe. It supports life by providing oxygen and regulating weather patterns essential for agriculture and water supply.
The Stratosphere Characteristics:
- Altitude: Extends from about kilometers to 50 kilometers (9 to 31 miles).
- Temperature: Increases with altitude, from about -60°C (-76°F) at the bottom to 0°C (32°F) at the top.
- Composition: Contains the ozone layer, which absorbs and scatters ultraviolet (UV) radiation.
- Features: The stratosphere is more stable than the troposphere, with few weather changes.
Importance:
The ozone layer within the stratosphere is crucial for protecting living organisms from harmful UV radiation, which can cause skin cancer and damage DNA.
The Mesosphere Characteristics:
- Altitude: Extends from about 50 kilometres to 85 kilometres (31 to 53 miles).
- Temperature: Decreases with altitude, reaching as low as -90°C (-130°F) at the top.
- Composition: Less dense, with fewer gases and decreasing oxygen levels.
- Features: Meteors burn up in this layer, creating shooting stars.
Importance:
- The mesosphere acts as a shield, protecting Earth from meteoroids by burning them up before they can reach the surface.
Thermosphere Characteristics:
- Altitude: Extends from from about 85 kilometres to 600 kilometres (53 to 373 miles).
- Temperature: Increases significantly with altitude, reaching up to 2,500°C (4,532°F) or higher.
- Composition: Very low density, with particles of oxygen and nitrogen.
- Features: Contains the ionosphere, where auroras occur. This layer is also where the International Space Station orbits.
Importance:
The thermosphere is important for radio communication as it reflects and modifies radio waves. It also contributes to the formation of auroras and stunning natural light displays.
The Exosphere Characteristics:
- Altitude: Extends from about 600 kilometres to 10,000 kilometres (373 to 6,214 miles).
- Temperature: Extremely variable; particles can be very hot or very cold.
- Composition: Sparse particles, mainly hydrogen and helium.
- Features: Gradually fades into outer space, with particles escaping into the vacuum of space.
Importance:
The exosphere is the transition between the Earth’s atmosphere and outer space. It helps to protect the Earth from cosmic radiation and solar winds.
Conclusion
The Earth’s atmosphere is a complex system of layers, each with distinct characteristics and functions. From the troposphere, where weather occurs, to the exosphere, which fades into space, each layer plays a critical role in sustaining life, protecting the planet, and enabling communication. Understanding the structure and features of the atmosphere is essential for appreciating its importance and the need to protect it from pollution and other harmful activities.
Class 7 Social Science Our Earth Notes Questions and Answers
Question 1.
What is the approximate temperature 3. at the centre of the Earth’s interior?
Answer:
The approximate temperature at the center of the Earth’s interior, in the inner core, is estimated to be around 5,500 to 6,000 degrees Celsius
Question 2.
What are the different sources of information used to study the interior of the Earth?
Answer:
analyzing volcanic materials, studying seismic waves, and examining meteorites, as well as magnetic fields and gravitational data.
Question 3.
Explain the Structure of the Earth
Answer:
Question 4.
What is the distance from the Earth’s surface to its centre?
Answer:
The average distance from the Earth’s surface to its center, or the Earth’s radius, is approximately 6,371 kilometers (3,959 miles).
Question 5.
Define Lithosphere
Answer:
The part of the earth that comprises the crust and upper part of the mantle is called the lithosphere.
Question 6.
What is Atmosphere?
Answer:
The part below the lithosphere, which is in a molten state due to the melting of rock particles (magma), is known as the asthenosphere.
Question 7.
…………. are the major gases in the atmosphere.
Answer:
Nitrogen, Oxygen, Carbon Dioxide
Question 8.
What do you mean by Evaporation?
Answer:
Evaporation is the process by which a liquid turns into a gas.
Question 9.
Explain any two layers of Atmosphere
Answer:
The Earth’s atmosphere has several layers, and two of them are the troposphere, the lowest layer where weather occurs, and the stratosphere, containing the ozone layer and where commercial aircraft often fly.
Question 10.
Define Hygroscopic nuclei.
Answer:
The fine dust particles in the atmosphere are called Hygroscopic nuclei.
Question 11.
What are the different sources from Ans: which we get information about the interior of the Earth?
Answer:
Different sources from which we get information on the Earth’s Interior are:
- From the materials reaching the Earth’s surface through volcanic eruptions.
- From the information collected from mines
- By analysing the motion of waves generated during an earthquake.
Question 12.
Differentiate the lithosphere and asthenosphere
Answer:
Lithosphere
The part of the earth that comprises the crust and the upper part of the mantle is called the lithosphere. The part below the lithosphere.
Asthenosphere
which is in a molten state due to the melting of rock particles (magma) and is known as the asthenosphere.
Question 13.
Explain the features of the Crust
Answer:
- The crust is the outermost and relatively thin layer of the earth.
- This layer is made up of solid rocks. The crust has two parts namely continental crust and oceanic crust.
- The continental crust is thicker than the oceanic crust.
- The average thickness is about 30 kilometres.
- In mountain areas, the continental crust has a thickness of about 70 kilometres, but the average thickness of the oceanic crust is 5 kilometres.
Question 14.
Explain the features of the Mantle.
Answer:
- Mantle is the layer below the crust.
- This is relatively thick.
- It extends up to about 2900 kilometres.
- The part of the earth that comprises the crust and upper part of the mantle is called the lithosphere.
- The part below the lithosphere, which is in a molten state due to the melting of rock particles (magma) is known as asthenosphere.
- The portion below the asthenosphere is in solid state.
Question 15.
Explain the features of the Core.
Answer:
- The layer below the mantle is the core. It is divided into outer core and inner core.
- The outer core is in liquid state while the inner core is in solid state.
- The core is mainly made up of metals like Nickel (Ni) and Iron (Fe). Hence the core is also known as NIFE.
- The temperature in the inner core is about 5500 degree Celsius.
Question 16.
Mark the Interior of the Earth in the given picture.
Answer:
A – Crust
B- Mantle
C-Outer Core
D-Inner Core
Question 17.
Match the following.
| A | B |
| The Crust | It extends up to about 2900 km |
| The Mantle | Also known as NIFE |
| The Core | Outer layer |
Answer:
| A | B |
| The Crust | Outer layer |
| The Mantle | It extends up to about 2900 km |
| The Core | Also known as NIFE |
Question 18.
What are the major components of the atmosphere?
Answer:
Nitrogen, Oxygen, Carbon dioxide etc., are the major gases in the atmosphere. Apart from these, there are other gases, dust particles and water molecules.
Question 19.
Explain the various ways by which dust particles reach the atmosphere.
Answer:
Main sources of the dust particles in the atmosphere are:
by wind
Through volcanic eruptions
Ash formed by burning of meteors
Question 20.
Explain atmosphere and atmospheric pollution.
Answer:
Atmosphere
The gaseous blanket that covers the earth is known as the Atmosphere.
Atmospheric Pollution
The mixing up of smoke, toxic gases and other chemicals in the air that alters the composition of the atmosphere is known as atmospheric pollution.
Question 21.
Explain the term Atmospheric pollution. What activities cause atmospheric pollution?
Answer:
The mixing up of smoke, toxic gases and other chemicals in the air that alters the composition of the atmosphere is known as atmospheric pollution.
Activities are:
- Smoke from Factories
- Vehicle Emission
- Burning of Plastic
- Stubble Burning
- Bursting of Fire cracks
- Volcanic eruption
Question 22.
Which are the layers of Atmosphere?
Answer:
- Troposphere
- Stratosphere
- Mesosphere
- Thermosphere
- Exosphere
Question 23.
Explain the features of Troposphere?
Answer:
- Lower most layer of the atmosphere.
- It has an average height of 13 kilometres from the earth’s surface.
- The height ranges from about 8 kilometres at the poles to 18 kilometres at the equator (because the temperature is high in the equatorial region)
- Dust particles and water vapour are most abundant in this layer.
- Atmospheric phenomena, such as cloud formation, rain, snow, wind etc., occur in this layer.
- The temperature of the atmosphere decreases at the rate of 1 degree Celsius for every 165 metres from the surface of the earth. This is called Normal Lapse Rate.
Question 24.
Explain the features of the Stratosphere.
Answer:
- This layer is just above the troposphere.
- The average height is about 50 kilometres from the earth’s surface.
- The temperature increases after a specific height.
- The ozone layer is in the stratosphere.
- It stands at an altitude of about 25 kilometres from the surface.
Question 25.
Explain the features of the Mesosphere.
Answer:
- This layer extends from about 50 kilometres to 80 kilometres above the stratosphere.
- Decrease in temperature with the increase in height.
- At an altitude of about 80 kilometres from the surface, the temperature drops to -100 degrees Celsius.
- The lowest temperature in the atmosphere is experienced here.
- Meteors that enter the Earth’s atmosphere burn down in this layer.
Question 26.
Explain the features of Thermosphere
Answer:
- It lies about 80 to 400 kilometres above the mesosphere.
- The temperature increases with an increase in altitude.
- The lower part of the thermosphere is called the Ionosphere.
Question 27.
Explain the features of Exosphere.
Answer:
- Uppermost layer of the atmosphere.
- The presence of air molecules in the exosphere, which lies above 400 kilometres from the surface, gradually decreases, and the layer becomes a part of Outer space.
Question 28.
Define Ionosphere.
Answer:
- At an altitude of about 80 to 400 kilometre in the atmosphere, intense solar radiation such as ultraviolet, X rays etc., converts the gas molecules into ions.
- This process is called ionization and the region where this process takes place is called the Ionosphere.
- Ions can conduct electricity.
- Radio waves are electromagnetic waves. Therefore, this region enables long distance transmission of radio waves.
Question 29.
What is the role of Ozone? Write the negative Impacts of Ultra Violet Rays?
Answer:
The presence of ozone gas in the atmosphere protects the earth by blocking the harmful ultraviolet rays from the sun. If ultraviolet rays reach the earth’s surface at an increased rate, it is harmful to living organisms and ecosystems.
Negative Impacts are:
- Collapse of the food chain
- Crop damage
- Stunting of plant growth
- Early aging
- Blindness, Cataract
- Skin cancer
Question 30.
When is Ozone day celebrated and what are the objectives behind that day?
Answer:
September 16 is observed as World Ozone Day. The objective behind observing this day is to create awareness among people about the need to protect ozone layer and to control the use of products that can cause ozone depletion.
Std 7 Social Science Our Earth Notes
- The temperature at the centre of the interior is about 5500 degrees Celsius
- The distance from the surface to the centre of the earth is about 6371 kilometres.
- The information regarding the interior of the earth is formed through scientific studies and inferences.
- Different sources from which we get information on the Earth’s Interior are:
- From the materials reaching the Earth’s surface through volcanic eruptions. From the information collected from mines
- By analysing the motion of waves generated during an earthquake
- Layers of the Earth are Crust, Mantle and Core.
- The gaseous blanket that covers the earth is known as the Atmosphere.
- Nitrogen, Oxygen, Carbon dioxide, etc., are the major gases in the atmosphere.
- Apart from these, there are other gases, dust particles and water molecules.
- As altitude increases, the amount of gases decreases.
- Oxygen, the life giving gas for humans and other living things, and Carbon dioxide that helps the survival of plants are obtained from the atmosphere.
- The process by which water from the earth’s surface is heated by the sun and reaches the atmosphere as vapour is called Evaporation.
- The presence of water vapour in the atmosphere is only up to 90 km from the earth’s surface. Water vapour condenses around fine dust particles in the atmosphere to form clouds. The fine dust particles in the atmosphere are called Hygroscopic nuclei.
- Main sources of the dust particles in the atmosphere are:
- by wind
- Through volcanic eruptions
- Ash formed by the burning of meteors
- The mixing up of smoke, toxic gases and other chemicals in the air that alters the composition of the atmosphere is known as atmospheric pollution.
- Layers of the atmosphere are Troposphere, Stratosphere, Mesosphere, Thermosphere and Exosphere.
- Negative Impact of Ultraviolet rays are:
- Collapse of the food chain
- Crop damage
- Stunting of plant growth
- Early aging
- Blindness, Cataract
- Skin cancer