Notes / SOLVED EXERCISES: GEOGRAPHY PTB -7
CH: 1) PHYSICAL STATE OF EARTH
Q.1: Explain the Composition of Earth’s Interior.
Ans: COMPOSITION OF EARTH’S INTERIOR
Geographer has no equipment to know about the internal structure of earth. For this reason, man has limited knowledge about it. Therefore, to know about internal structure of earth, man depends on seismic waves, magnetic and gravitational force of earth. The distance between the surface and centre of earth is more than 6000 kilometres. The temperature gradually increases towards the centre of earth.
COMPOSITION OF EARTH’S INTERIOR
The internal part of earth is divided into three important parts.
Crust 2. Mantle 3. Core
DETAIL OF COMPOSITION OF EARTH’S INTERIOR
The detail of internal structure of earth is given below:
CRUST
The upper layer of earth is called Crust. This surface of earth consists of both water and dryness and its thickness his not uniform. Its thickness is in between 8 to 40 kilometers.
DIVISION OF CRUST
Crust is divided into two parts. The upper part is known as continental shelve. While lower Portion is known as Oceanic shelve.
Continental Shelve
The layer of earth on which human beings live is called continental shelve. The continental shelve consists of a number of landmasses, which are known as continents. It is made of Silicon and Aluminum, that is why it is also known as Sial.
Oceanic Shelve
The part of earth crust, which is below the seas, is called oceanic shelve. Oceanic shelve is made of Silicon and Magnesium, that is’ why it known as Sima. This portion of earth is rich in minerals.
MANTLE
Below crust there is a thick layer, which is called Mantle. Its thickness is 2900km.
DIVISION OF MANTLE
Mantel consists of two layers. Upper layer is upper mantel and lower layer is called lower mantel.
Upper Mantle
Upper mantle is less thick as compared to lower mantel. It thickness is 670 kilometres. In upper mantel most of the rocks are found in liquid state.
Lower Mantle
Below the upper mantle is lower mantle. Its thickness is 2230 kilometres. Upper Mantel is hard and solid. Mostly it is composed of iron, silicon and magnesium.
CORE
Below the mantel, there is another layer, which is called Core. The core is a layer rich in iron and nickel found in the interior‘ of the Earth. The core is about 7,000 kilometres in diameter.
DIVISION OF CORE
Core is composed of two sub-layers:
Outer core ii. Inner core
Outer Core
The thickness of outer core is 2250 kilometers. This layer is in liquid form exact below the mantle.
Inner Core
This core is solid and heavy than other core and its thickness is 1220 kilometers. This is in solid form. This is also known as knife. This name is made with the initial words of both iron and nickel.
Q.2: Write a short note on the movements of Plate Tectonics and write their names.
Ans: PLATE TECTONICS
Thousands of year ago all continents were intact with each other because of which there was only one continent, which is known as Pangaea. Due to motion of tectonics plates, this big continent was shaped further and divided into a number of continents.
STRUCTURE OF OUTER LAYER OF EARTH
In 1960 the geographers used two new terminologies for the exterior composition of earth, their names are:
Lithosphere 2. Asthenosphere
LITHOSPHERE
Lithosphere consists of the upper surface of earth and solid upper portion of mantle.
ASTHENOSPHERE
Under lithosphere, there is soft layer of rocks, which is known as Asthenosphere.
Division of Lithosphere
Lithosphere is divided into seven active parts, which are known as plates. The Big plates of curst are as under:
Pacific plate ii. North American Plate
iii. South American Plate iv. Eurasian Plate
African Plate vi. Australian Plate
vii. Antarctica Plate
Q.3: What are Faults? In addition, explain Types of Faults.
Ans: FALTS
Big cracks or spaces on the earth’s surface are called faults. Typically, these cracks are the boundaries among plates. Inactive faults had movement along them at one time, but no longer now. The type of motion along a fault depends on the type of fault. The aera where a fault is formed is known as fault zone the crack that exists in fault zone is known as fault line.
RING OF FIRE
Most of the earthquakes are occurred in Pacific plate. This area as surrounded by crakes, therefore its also known as “Ring of Fire”. Faults are made only in weak area and the place of fault is known as fault zone. Crakes in fault zone is called as fault line.
TYPES OF FAULT
There are three types of faults:
Normal Fault 2. Transform Fault 3. Reverse Fault
Normal Fault
When parts of crust are moving in opposite direction and due to removal of upper layers, this fault is called Normal Fault. In this condition, lava burst out through the weak
portions of earth and volcanic eruption occurs.
Transform Fault
When parts of plates move they collide with each other. Such types of fault is called transform fault. In this fault no part of earth move up or down. When plates move towards each other then reverse fault occurs. In this way, because of inside pressure earthquakes and eruption of volcanoes occur. In this way, the plates become close to each other and usually rocks come into existence.
MAJOR PLATE FAULTS IN PAKISTAN
In Pakistan, two major plates are intact e.g. Eurasian plate and Indian plate. These plates move towards each other. Fault line, which lies in Pakistan, separates Eurasian plate from Indian plate. Therefore, this region is earthquake prone region. The earthquake of 8th Oct, 2005, occurred because of motion in these plates due to which hundreds of thousands people died in this earthquake and there was a great loss of lives and property. In future, this region has also become centre for both small and big earthquakes.
Q.4: Discuss the effects of earthquakes.
Ans: CAUSES OF EARTHQUAKES, THEIR EFFECTS AND THEIR DISTRIBUTION
EARTHQUAKE
A sudden violent shaking of the earth’s surface is known as earthquake.
OCCURRING OF EARTHQUAKES
Due to movements in internal structure of earth, it creates both vibrations and buoyancy. Earthquakes are caused due to movement in any part of earth. The waves of earthquake travels in all direction from the originated place. The waves of earthquake becomes weak as they are in at a distance from the origin.
CAUSE OF EARTHQUAKE
These are the major causes of earthquake.
Movements of Plates
Mostly, earthquakes come due to the sudden movements of plates. When these plates collide with each other when vibration occurs on the surface of land. Anywhere in the world where there is fault, that line becomes a centre for earthquakes.
Volcanism
Earthquakes also come due to volcanism. When lava bursts out by breaking weak surface of earth, then movement on the surface of earth occurs.
EFFECTS OF EARTHQUAKES
Earthquakes are the disaster, which cause a lot of destruction. Some important factors are mention below.
Loss of Both lives and Material
Buildings destroy due to earthquakes. People become inured and lose of both lives and materials.
Effect on Agriculture
Due to earthquakes sources of irrigation are affected, standing crops are destroyed.
Effect on System of Electricity
Due to earthquakes the system of electricity, water and gas is disturbed.
Bursting of Fire
Due to earthquakes sometimes, fire bursts due to electricity and gas.
Hurdles in Rescue
Due to earthquakes, hurdles occur in the activities of rescue.
Cause of Floods
Due to earthquakes, there is also threats of floods.
Effects on Transportation
Due to earthquakes, the facilities of transportation are interrupted due to the destruction of bridges and roads.
Q.5: Make a table of larger earthquakes in Pakistan and the world.
Ans: DISTRUBITION OF EARTHQUAKES IN THE WORLD.
FIRST BIG CENTRE OF EARTHQUAKES:
In the world, mostly earthquakes come around the areas of Atlantic Ocean. In this area the small and big cracks of earth crust are existed. The picture of these cracks presents a look of a circle or a ring. The areas of Alaska Alvin, Japan, Mariana, Philippine and New Ghani etc. are included in it.
SECOND BIG CENTRE OF EARTHQUAKES:
The other big centre of earthquakes is Trans Eurasian crack in the world. These cracks reach till Turkey, Gulf of Persia while passing through Himalaya and Indonesia Islands. One Northern and central Western part of Pakistan also come in the centre of these earthquakes.
THE GREAT EARTHQUAKES OF THE WORLD AND PAKISTAN
Nos.
Year
Place
Devastating on 11, wastage of Richter Scale Lives
1
1920
Gan Su, China
8.6
2,00,000
2
1923
Kantu, Japan
7.9
1,43,000
3
1927
Shanghai, China
7.9
2,00,000
4
1932
Gan su, China
7.6
70,000
5
1935
Quetta, Pakistan
7.5
30,000
6
1948
Turkmensistan
7.3
1,10,000
7
1976
Tangestan, China
7.5
2,55,000
8
1990
Iran
7.7
40,000
9
1999
Turkey
7.6
17,000
10
2003
Iran
6.6
31,000
11
2004
Island of Northern Sumatra, Indoneshia
9.0
2,83,000
12
2005
Kashmir and Areas of Pakistan
7.6
80,000
13
2010
Haiti, Central
7.8
1,50,000
Q.6: Discuss the Instruments used to Measure Earthquakes.
Ans: INSTRUMENTS AND SCLAES USED TO MEASURE EARTHQUAGES
SEISMOGRAPH
An instrument is used to measure intensity of earthquake is known as seismograph. The intensity of earthquakes is measured through Richter Scale.
RECTOR SCALE
To measure big intensity of earthquake is a scale, which is called rector scale.
Q.7: Analyze Volcanism and its Effects.
Ans: VOLCANISM
The hot eruption of Sial (Magma) from the surface of earth is known as volcanism. While this process takes place the -underground volcanic magma comes out on the surface of earth in the form of lava. In this process, different types of liquid rocks and gases are included.
OCCURRING OF VOLCANISM
Volcanism mostly occurs along the crakes of earth as volcanoes are mostly found on the boundaries of the plates of earth. About 70% of volcanoes are found on the bed of sea but due to their presence in sea we cannot see them.
EFFECT OF VOLCANISM
These effects of volcanism are given below:
Formation Mountains
Volcanoes are formed in volcanism process. The layers of lava and perennial volcanism raise these volcanoes. By this activity Mountains are formed.
Deficiency of fertility of Land
When lava erupts from volcanoes it makes the land barren. The matter of lava expends all surrounding area. Therefore, no crop can grow.
Atmospheric pollution
The matter, gases etc. which eruts from volcanoes make the atmosphere of
surrounding areas polluted which effect both human and botanic lives.
Incensement of temperature
Sometimes in volcanisrn different types of gases, clouds are released rapidly because of high temperature.
Deforestation
When lava erupts molten rocks excret rapidly, which burn everything. Due to this activity, fire bursts and deforestation accrues.
Loss of both lives and material
Buildings destroy due to earthquakes. People become injured, and loss of both lives and materials occur.
Q.8: Explain Types of Volcanoes and their Distribution.
Ans: TYPES OFVOLCANOES AND ‘THEIR DISTRIBUTION
The hot eruption of Sial (Magma) from the surface of earth is known as volcanism.
Volcanoes are of three types, their detail is as under:
ACTIVE VOLCANOES
The volcanoes in which the volcanism is in continues manner is known as active volcanoes. These volcanoes are usually erupt lava e.g. Fujiyana (Japan), Visuvious (Italy) etc.
DORMANT VOLCANOES
Dormant volcanoes are those in which a long period has gone being erupted but volcanism can occur anytime in these volcanoes. Such, type of volcanoes are very dangerous.
EXTINCT VOLCANOES
The extinct volcanoes are those volcanoes in which eruption of lava has stopped and there are no chances of lava eruption.
DISTRIBUTION OF VOLCANOES
Distribution of Volcanoes
Volcanoes are found on the p1ate’s cracks of earth. Most of the volcanoes are found in the surrounding areas of the Pacific Ocean.
First important region
Coastal areas of Pacific Ocean, in particular the eastern islands are mostly formed, with volcanism. This portion in known as “Ring of Fire”.
Second important region
Trans-Eurasian is the second most important area where volcanoes are found.
Third important region.
Third important region
The area of Australian plate, Eurasian plate and Pacific Ocean plate is included the third most important are of volcanoes is between sea areas. It is in between Atlantic and Indian Ocean. This rocky area is formed due to volcanism. It is also known as the mid-Atlantic rock range.
IMPORTANT PINTS
The internal Structure of earth is found through waves of earthquakes magnetic force of earth and its gravitational force.
The upper surface of earth is known as crust, and its thickness is in between 8 to 40 kilometres.
The thickness of upper mantle is 670 kms and thickness of lower mantle is about 2230 kms.
The external core of earth consists of mostly liquid rocks, and its thickness is about 2250 kms.
The internal core of earth is made of iron and Nichel, and its thickness is about 1220 kms.
Crust is divided into seven big plates.
Big crakes and spaces in earth, is known as fault.
Fault forming area is known as fault zone and crake in fault zone known as fault line.
The area around pacific plate is also known as “Ring of Fire”.
In normal fault, the parts of crust are moving in opposite direction, to and fromotion in transform fault and towards each other in reverse fault.
The instrument to measure earthquakes intensity is seismograph.
The scale to measure earthquake‘s intensity is Richier’ Scale.
The eruption of hot Sial matter (magma) from the surface of earth is known as volcanism.
Those volcanoes in which volcanism is going on are known as active volcanoes.
A time has been passed after lava eruption in dormant volcanoes but that can be occurred again.
Those volcanoes in which continues eruption is stopped, known as extinct volcanoes.
A large number of volcanoes are found around the areas of Pacific Ocean.
CH: 2) DENUDATION
Q.1: Write a note on denudation and it types:
Ans: DENUDATION
Destruction of earth’s upper surface and underground areas appearance on the earth’s surface is known as “Denudation”.
PROCESS OF DENUDATION
Internal forces of earth exposed some internal area, its external elements like river, glacier, Wind, blazing sun and frost begin to level that area by worn and torn process and transport that debris from its original place to new one.
“Denudation” is the term used for all those elements which torn the earth surface, Waste the earth‘s elements, transfer it to some other place.
TYPES OF DENUDATION
There are three/types of weathering.
a) Physical weathering
b) Chemical Weathering
c) Biological weathering
PHYSICAL WEATHERING
The process in which rocks are broken down into small fragments and pieces is called Physical weathering. This process is directly of indirectly more dependent on weather conditions, intensity of sun light, snow at rainfall.
Following are the types of Weathering
TYPES OF WEATHERING
Following are the types of Weathering.
Physical or Mechanical Weathering
If the weathering takes place due to natural elements, this type of weathering is called Physical or Mechanical Weathering.
METHODS OF PHYSICAL OR MECHANICAL WEATHERING
(i) Temperature Change
Hot temperatures can give rise to thermal expansion in rocks and cool temperatures can cause rocks to contract. In areas such as deserts where the temperature is hot during the day, rocks get hot and can expand by a small amount. During the night’ the temperature can drop significantly making it very cold and so the rocks contract. This continuous expansion of the rock during the day and contraction during the night exerts stress on the rock and cracks form eventually causing pieces of the rock to fall away.
(ii) Freeze-thaw
Water expands when it freezes. So when water enters the cracks in a rock and freezes, it expands and pushes the cracks further apart. When the water melts, in can travel further into the bigger cracks making the cracks even bigger when the water freezes again. This process occurs continuously until the crack is big enough to break a piece of the rock off. The animation below shows the weathering action of water freezing and thawing in a rock.
(iii) Wind, Rain and Waves
Wind can carry small particles or sand and rocks such as in sandstorms in deserts. When these particles collide with rocks, they can wear them away. Rainfall can also wear away at rocks as can the action of waves over a long period.
Chemical Weathering
Chemical weathering occurs when rocks are broken down by a chemical change.
(i) Hydrolysis.
Rainwater can become slightly acidic by absorbing carbon dioxide in the atmosphere and this reacts with the mineral grains in the rock-giving rise to new minerals and salts. It is the reason that breakage and destruction due to chemical process is known as chemical weathering.
(ii) Acid Rain
Biological Weathering
Biological weathering takes place when living organisms wear rocks away. Trees and other plants can grow within the cracks in a rock formation. As the roots grow bigger, they push open cracks in the rocks making them wider and deeper. Over time, the growing tree eventually prizes the rock apart.
Breakage of Rocks
Tiny organisms like bacteria; algae and moss can grow on rocks and produce chemicals, which can break down the surface layer of the rock. Burrowing animals such as rabbits can accelerate the formation of cracks.
Q.2: Write down the reasons for erosion process.
Ans: EROSION
Cutting of the features of earth surface is known as erosion.
ELEMENT OF EROSION
Following are the elements are the erosion.
Water – Wind – Glacier – Soil – Sea – Water Erosion
Water erosion occurs from the chemicals in the water, and the force of the flow of water in the river. There are many chemicals in the water of a river, and those chemicals can break down certain rocks, such as limestone or chalk. This eroded rock is carried down the river.
Wind Erosion
Wind erosion, rocks and pebbles are carried by the wind and can hit landforms, eroding materials off them that are carried off in the wind.
Glacier Erosion
Ice erosion, besides that of hail, comes mostly in the form of glacier erosion. Glaciers are giant bodies of ice that can pick up huge pieces of rock, some even as big as houses. A combination of the water, ice, and picked up sediment, create a powerful eroding machine.
Sea Erosion
Erosion in the Sea also occurs. The salts and other chemicals can erode weak rocks on the coast, such as limestone and chalk. The eroded materials are carried up the shore by the means of alongshore drift waves crashing against the shore- can create air pressure inside cracked rocks that can eventually break them.
Soil Erosion
Soil erosion pays the biggest price to farmers. Flooding, wind etc. can carry the topsoil away from farmlands, and make the soil unfertile
MASS WASTING
Rocks stuff travels with gravitational force of earth towards the lower area, which is known as mass wasting. The shape of rock are distorted by weathering process. The rocks stuff travels faster on some good slopes with the help of gravitational force as compared to the area of not good slope with the help of gravitational force as compared to the area of not good slope and this process continues. Soil fluctuation and muddy flow etc. are the prominent movement of mass wasting. Rockslide is the rapid and sudden downward, movement of rocks or boulders along a steep slope under the influence of gravity.
TYPES OF MASS WASTING
► Soil fluctuation ► Flow of Mud
► Flow of Soil ► Flow of Slime
Soil fluctuation
Soil fluctuation is slow in mass wasting while speed up muddy flow due to water. The soil fluctuation is slowest movement in mass wasting. We cannot estimate its speed. Soil fluctuation is common in hilly and semi-hilly regions. Usually in this kind the crack appears on the comers of roads and road are destroyed. The panels of electricity and wires are inclined.Gravitational force of earth plays an important role in moving erosion stuff.
Flow of Mud
Water has importance in soil fluctuation. Mass wasting usually occurs in rainy areas. Soil fluctuation happens on sharp slide and within few hours a portion of mountain flows downwards. Mass wasting is the flow of specific kind of sprinkle and mud that is an environmental problem. This mud is a kind of soil sprinkle stream. The weak and soft minerals of rock are flowed by the rain water. Some processes take place in few hours and the villages, and other features come in their way are disappeared forever.
It often results in road blockages, endangering lives and seriously interrupting communication and transportation.
Land Sliding
The fall of big and small rock materials from height towards downwards is known as land sliding. Usually both the height and slope is large in it. Rocks become weak by weathering and due to gravitational force the stones start to fall downwards.
Disadvantages of Land Sliding
Due to land sliding the paths are blocked.
Roads and building are distorted
If the land slide is big enough, then it might stop the path of rivers.
Due to a big land slide a lake is formed in Atta Abad near Hunza valley.
Q.3: What are the impacts of erosion process and mass wasting on agriculture, irrigation, human settlement and transportation?
Ans: The impacts of erosion and mass wasting on agriculture, irrigation, human
settlement and transportation are explained as following:
IMPACT ON AGRICULTURE
The irrigation system, consists of muddy canals and small streams, continuously faces erosion of water.
Mass wasting. and soil erosion result in the loss of surface topsoil, which is essential for growth of vegetation. As a result, more areas become barren.
The production of crops reduces.
Reduction in the shelters of wild life and pastures on mountains also takes place.
Erosion and mass wasting destroy wild life.
Erosion and mass wasting destroy mountain meadows.
IMPACT ON IRRIGATION
Erosion and mass wasting leaves great impact on irrigation. Some of them are given below:
A huge amount of mud piles up at the bed of canals due to erosion of water which reduces the quantity of water in canals.
The continuous transfer of material along with water fills the base of dams with mud and capacity of storing water reduces.
Due to erosion and mass production of electricity is affected.
IMPACT ON HUMAN SETTLEMENT
Erosion and mass wasting leaves great impact on human settlements-
Some are –given below:
Usually there is a loss of both lives and economy because of land sliding
and flow of mud in hilly areas. In 1985, a number of villages are abolished under the debris of earth in Columbia. Such accidents usually take place in northern area of Pakistan.
IMPACT ON TRANSPORTATION NETWORK
The dwellers of hilly areas are facing earth’s movement and land -sliding on continuous basis due to which the roads are blocked and inhabitants. of hilly areas are disconnected from the rest of world. It effects efficient system wan to from the rest of world. It effects traffic system worst.
Q.4: Suggest the Ways to Minimize the impacts of Reducing erosion process and mass wasting.
Ans: MEASURES TO CHECK MASS WASTING AND SOIL EROSION
Since the impact of mass wasting, especially landslides, is so severe, some measures can be taken to avoid accidents.
Chunam plaster for cement can be spread on steep slopes.
Gradients of steeper slopes could be reduced.
Potentially unstable rocks or soil masses should be removed.
Retaining walls or structures can be built to hold back possible slides.
Steep slopes ‘should be inspected regularly, especially during periods of heavy or prolonged rainfall.
More surface drainage channels and ditches can be constructed.
Dangerous slopes should be abolished.
Subsurface drainage systems may need to be constructed or improved.
Legislation can restrict development and building in dangerous zones.
Vegetation can be planted on steeper slopes.
Instruments can be installed to check slope instability, providing early warning in areas of concern.
CH: 3) INTRODUCTION TO ATMOSPHERE
Q.1: Explain the composition of Atmosphere.
Ans: ATMOSPHERE
Then thin envelope of air that surrounds our planet is a mixture of gases; this cover of gases is called Atmosphere. Due to gravity, Atmosphere has surrounded our earth in the form of cover. Due to gravity, Atmosphere is attached to earth from all sides. The survival on our galaxy earth is due to atmosphere. Three basic elements, which are ingredients of atmosphere, are regular gases, Variable gases and Polluted gases. These are mostly found on the lower surface of atmosphere.
NITROGEN & OXYGEN
Atmosphere is a combination of a number of gases. These gases are directly or indirectly essential for survival of atmosphere. About 90% of atmosphere consists of these two gases Nitrogen & Oxygen, therefore the percentage of rest of gases is only 1%. Importance of Nitrogen
The fertility of soil depends on Nitrogen. Nitrogen is necessary nourishment of plants. It helps in controlling fire.
VARIABLE GAES
No one can deny the importance of variable gases. Variable gases include Carbon dioxide, water Vapours & ozone. Carbondioxide is heavy than other gases. The quantity of carbon dioxide has increased in last two hundred year about 25%. The burning, of energy sources for example coal, oil, natural gas etc. produce smoke which increases the quantity of carbon dioxide in atmosphere. In this way the atmospheric temperature also arises which is harmful for survival of life. It affects world’s atmosphere. The other variable gas is Ozone O3. Ozone gas is about l7 to 50 km above in atmosphere.
Importance of Ozone
Ozoneabsorbs the bulk of solar ultraviolet rays from sun to reach earth. In the absence of ozone layer, such ultraviolet rays having energy become dangerous for life on earth. Such extreme energy carrying rays can cause Cancer & Eye diseases. The ultraviolet rays before reaching earth are filtered through ozone.
POLLUTION
Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the, form of chemical substances or energy, such as noise, heat or light. Pollutants, the components of pollution, can “be either foreign substances energies or naturally occurring contaminants. Pollution is often classed as point source or nonpoint source pollution.
Air contains pollution. Minute particles are found in air. The smoke from factories and vehicles contains a huge amount of carbon dioxide, Sulphur and carbon dioxide etc. During burning process the smoke enters into air, which pollutes it.
Effect of Pollution
The atmosphere of industrial cities is affected with pollution. This is dangerous for health. The diseases of throat and breathing increases with it. Such gases are also included in polluted gases, which are destroying the ozone gas, and reduction in ozone gas takes place. The dust particles also fly with polluted gases. Their quantity is not uniform. Their quantity is greater in desert as compared to humid area. Their quantity is also large in both urban and rural areas.
WATER VAPOURS
In atmosphere, water Vapours are important part of variable gases. Water Vapours not only absorb heat but also help in transferring of heat from one place to another. Water Vapours are present in atmosphere in the form of gas. If water Vapours do not exist in atmosphere then there will be no cloud and rain.
The system of life depends on it. Earth absorbs heat from sun and through the process of vapourization the water Vapours are added into air from sea and other water bodies. Their presence in atmosphere depends on temperature. If the temperature increases then the quantity of water Vapours also increases and the presence of water Vapours moderate both ’ heat and coldness of atmosphere.
Q.2: Explain the importance of carbon dioxide and oxygen.
Ans: IMPORTANCE OF OXYGEN
Oxygen is necessary for life. When we take oxygen into our lungs, we absorb oxygen in our bodies. Immediately, this gas dissolves with other chemical elements. This gas is absorbed in our blood and directly after chemical reaction with our food gives us energy. The survival of life is not possible Without of Oxygen. Oxygen helps in burning all kinds of energy resources for example, coal, and Natural gas.
Importance of Carbon Dioxide
Carbon dioxide is necessary for life. Interaction of this gas with other gases makes’ carbohydrates, which is necessary for the nourishment of both plants and animals. Carbon dioxide moderates. the temperature by absorbing heat.
Q.3: Discuss in detail the Layers of Atmosphere.
Ans: THE LAYERED STRUCTURE OF ATMOSPHERE
The atmosphere is divided vertically into four, layers based on temperature: the troposphere, stratosphere, mesosphere, and thermosphere.
TROPOSPHERE
The nearest layer of the Earth’s atmosphere is the troposphere. It contains 90% the mass of the atmosphere and almost all of the atmospheric water. All kind of climatic changes, which include clouds, rains and winds, are which moderates the atmosphere.
Most of the gases, water Vapours and dust particles are present in the same layer. The temperature in upper portion of this layer is about 60 degree centigrade. The temperature drops about 6.5 degrees Celsius for every kilometer above the earth’s surface. Its presence is about 16km above earth surface.
STRATOSPHERE
Above troposphere is stratosphere. This layer contains the ozone, layer. Ozone acts as a shield for the earth’s surface. It absorbs ultraviolet radiation from the sun. Instead of increasing temperature on height the temperature decreases and on its boundary temperature reaches to 0 degree centigrade. The air here is very dry, and it is about a thousand times thinner here than it is at sea level. Because of n that, this is where jet aircraft and weather balloons fly. This layer of atmosphere is about 16 to 50km above troposphere.
MESOSPHERE
Above stratosphere, there is mesosphere. The top of the mesosphere, called the mesopause, is the coldest part of Earth’s atmosphere with temperatures averaging about minus 100 degree centigrade. The presence of other gases in air and particles are in minute amount at this stage. This layer is about 50 to 80 kilometres in atmosphere
THERMOSPHERE
The thermosphere is located above the mesosphere. Thermosphere layer extends from 80 kilometres to the final boundary of atmosphere. The temperature increases towards height in this portion of atmosphere. At the height of 350 kilometres the temperatures is recorded about l00 degree centigrade.
DIFFERENCE BETWEEN WEATHER AND CLIMATE
Weather
The whole condition of temperature, atmospheric pressure, speed of air, humidity and particles in air of a particular place, is known as weather. Weather changes with time.
Climate
Climate is the average weather conditions of pa particular place for a long time.
Difference
The only difference between weather and climate is that Weather is the atmospheric condition of particular time of some place while the climate is the atmospheric conditions of particular place for a long time.
Q.4: Discuss in detail the change in climate on the earth surface.
Ans: CLIMATE CHANGE OVER THE EARTH SURFACE
The atmosphere of the earth changes due to activities of humans. Man makes roads, buildings and dams etc. as it’s his need. In 2009, a conference Was commenced in Copenhagen the capital of Denmark on the issue of atmosphere changes in which a number of countries participated. A number of decisions were made in conference to minimize the emission of carbon dioxide in order to have control over increasing temperature on earth. A specific amount of CO2 is necessary for life on earth but the increase in quantity of CO2 is up to a dangerous level. Increase in the quantity of CO2 and other dangerous gases in atmosphere are due to burning of energy sources e.g. coal, oil, natural gas etc. CO2 and other gases absorb the heat evolved from earth and ultimately temperature of earth increases, which is harmful for life. In this way the changes in atmosphere of the world occur. When volcanism takes place then dust particles and gases etc. enter into air in a huge amount, which ultimately results in atmosphere changes.
Q.5: Explain the importance of Ozone Layer.
Ans: SIGNIFICANCE OF OZONE LAYER
One of the atmospheric gases is Ozone. Ozone is made and ended naturally. Ozone absorbs ultraviolet rays and sends them to earth after filtration. In this way Ozone saves mankind form ultraviolet rays. It causes skin cancer and eye diseases. If the amount of Ozone decreases, the ultraviolet rays without filteration will reach the earth, which is harmful for life. So, the presence of ozone is necessary.
CAUSES OF OZONE EDEPLETION
The information collected from satellite helps in studying Ozone gas. The layer of ozone becomes, thick at different places. One of the main causes for reducing and destroying ozone gas is CFC gas which is mixture of Chloroflouro Carbon. There are fluorine and carbon items to keep in it. The activities of mankind also damaging ozone gas. CFC is used in refrigerator cool and in ‘different kind of sprays. Sometimes CFC is
released and damages Ozone worst.
Q.6: Suggest the Measures to Control Reduction of Ozone.
Ans: MEASURES TO OVERCOME THE PROBLEM OF OZONE DEPLETION
Due to efforts of different countries, there are some better results in reducing CFC and other dangerous gases in last few years. The information gathered from NASA and other sources to study about earth shows that the reduction in ozone gas is in lower pace. The main reason for this reduction is minimized use of CFC and then complete ban on it.
Now the other gases are used instead of CFC. For example, the use of HCFCs gas which is a mixture of carbon, hydrogen, chlorine and fluorine. This gas is less injurious as compared to CFC.
CH: 4) ATMOSPHERIC TEMPERATURE
Q.1: Describe atmosphere temperature.
Ans: ATMOSPHERIC TEMPERATURE
Sun is a big source of heat and Light. Sunrays give heat along with 1ight. Survival of life on earth is due to its heat and Light. When these rays pass through atmosphere about 50% of them are reflected in atmosphere, therefore about half of them reach our earth. When these rays strike against earth, few of them are reflected back and few are absorbed by earth. Absorbency of heat makes the earth hot. Hot earth transfers heat into atmosphere and air becomes hot.
Due to spherical shape of earth, some rays fall in curve manner on earth while some fall vertically. The curved rays have to cover more distance to reach earth. Most of them are absorbed by air and a small amount of heat reaches earth. On the other hand, the vertical rays have to cover less distance; therefore, less amount of heat is absorbed in air and more amount of heat reaches earth.
The curved rays stretches in more space, therefore their intensity is low. Vertical rays fall on small portion of earth; therefore their intensity is high. Due to these two reasons, temperature does not go high with curved rays but increases due to vertical rays. In this way the equatorial areas are hot due to vertical rays and arctic areas are cold due to curved rays.
Q.2: Define Temperature and Explain the Measurement of Temperature.
Ans: TEMPERATURE
The measurement of degrees of hotness and coldness of a particular place is known as temperature. In geographical terminology the meaning of temperature is the temperature of the air.
SCALE AND INSTRUMENTS USED IN MEASUREMENT OF TEMPERATURE
THERMOMETER
Thermometer is made of narrow glass tube in which an appropriate amount of mercury is filled and tube is evacuated to remove air pressure. This tube is divided into different grades. Liquid expands on heating and contracts on cooling. According to this principle mercury or alcohol inside the tube expands and contracts and indicates different readings.
Scales
In order to measure the temperature usually two scales are used:
Celsius Scale
Fahrenheit Scale
Thermometer has three main levels.
Boiling Point 2. Freezing Point 3. Absolute Zero
Boiling Point:
Boiling point is the temperature at which water starts boiling.
Freezing Point:
Freezing point is the point at which water starts turning into ice.
Absolute Zero
Absolute zero is the minimum possible temperature of some liquid. It is impossible to have temperature low than absolute zero.
HEATING OF EARTH AND THE ATMOSPHERE
Surface of earth is not uniform. Some places have water and some places are dry. As compared to wet places the dry places become hot and cold rapidly. It is the main reason of their hotness and coldness. The sunrays directly heat the earth without heating the atmosphere. The earth transfers this heat back to the atmosphere. As a result, the lower portion of atmosphere is hotter. And the upper portion is cooler. Earth absorbs heat during daytime and releases it at night. Those areas, which are covered by snow, reflect the sunrays in huge amount while the areas with dark colours absorb heat and reflect few amounts of sunrays. Such dark areas are competitively hotter than other regions. When the earth releases the absorbed sunrays, the heat is transferred to atmosphere.
Q.3: Explain the Vertical Distribution of Temperature.
Ans. VERTICAL DISTRIBUTION OF TEMPERATURE
The sunrays heat the earth. The earth transfers heat to the lower portion of the atmosphere. It after that heat takes time to reach the upper portion. -Still then loses its intensity when it reaches the upper portion. Therefore, lower portion is hotter than the upper portion. That is why the higher we go to cooler is it. Upwards temperature keeps on falling. This as known as the vertical distribution of temperature.
At every thousand metre height the temperature falls by 6-5 degree. The earth’s surface has seas, deserts, plains, forests and mountains on it. Because of this variation, the temperature ratio also varies from place to place. At dawn and sunset the sunrays do not fall vertically on the earth, therefore, there is less heat at these times. On the other
hand, at 120, the sunrays fall vertically on earth, therefore
there is more heat.
Q.4: What is Air Pressure?
Ans: AIR PRESSURE
The pressure of air is more on the lower portion of the atmosphere. High pressure of air results into rising of temperature while low air pressure keeps the temperature low. The air of low areas is more dense. This air contains heavy gases. The density of air decreases gradually at heights. Light gases enter in the air, which cannot absorb heat as compared to heavy gases. Because of this reason temperature keeps on falling with
heights.
Q.5: What do you mean by Inversion of Temperature Explain with Example?
Ans: INVERSION OF TEMPEATURE
The reverse situation of temperature is known as inversion of temperature.
Explanation:
Due to vertical distribution of temperature, it decreases with height but at certain places, it reverses and temperature rises with height as for example if the temperature at earth surface is 5oC, then it is 7oC above this point, which is inversion of temperature.
Q.6: What is reason of Inversion of Temperature?
Ans: REASON OF INVERSION OF TEMPERATURE
Through out the year equatorial regions remain hot and average temperature is 32oC. On contrary arctic regions are prone to coldness and temperature falls from freezing point. Such unequal distribution of temperature on the earth’s surface is known as horizontal distribution of temperature. On the basis of horizontal distribution of temperature the earth’s surface is divided into three zones.
Tropical Zone
It is a hot region, which stretches on both sides of equator. It stretches from the topic of cancer on northern side to the topic of Capricorn on southern sides.
Temperature Zone
Temperature Zone extends from mid of Arctic Circle on northern side to mid of Antarctic Circle on southern side. This region is neither too cold nor hot.
Torrid Zone
Torrid Zone stretches from mid of Arctic Circle in northern hemisphere to mid of Antarctic circle in southern hemisphere. This region is very cold.
Q.8: Elaborate the Factors Affecting Temperature.
Ans: THE FACTORS INFLUENCING HORIZONTAL DISTRIBUTION OF TEMPERATURE.
Following are the factors influencing horizontal distribution of temperature:
WET ARID DRYNESS
There is 71% water, and 29% dryness on the surface of the earth. The continents and dry places become hot rapidly. Continent and dry places become cold within short span of time after the sunset, on the other hand water or sea takes time to hot or cold. The dry places become hotter during summer as compared to water. It is so because of difference of physical features of the earth.
SUNRAYS
The rays of the sun fall vertically on equatorial regions. These vertical rays cause more heat in comparison to the rays, which fall in a curve manner on Polar Regions. As a result of that these regions have very low temperature.
WIND AND SEA CURRENTS
Winds travels from hot regions to cold regions and from cold regions to hot regions. The examples of these winds are land and sea breezes, mountainous breezes and valley breezes. Although the weather of Karachi is moderate but when Quetta cold wins hits it, there is coldness in Karachi. Sea currents travel both from hot to cold and cold to hot regions. When a hot wave after travelling reaches some area it increases temperature of that area. For example when a hot wave of northern Pacific Ocean after traveling reaches the western coast of Europe, it increases its temperature, due to this reason; this coast does not freeze even in winter season. Cold current reduces temperature of hot regions. For example, when a current flows along western coast of Africa is reduces its temperature.
CLOUDS
Clouds are a hindrance, in the way of most sunrays as they reflect them and a few amount of sunrays reach earth, which reduces temperature of earth. Therefore the cloudy areas have low temperature as compared to the cloudless areas.
COASTAL
Coastal region do not become hot even if they are situated near equator because of sea breeze. Being coastal area Karachi has moderate temperature throughout the year while the temperature of Lahore increases during summer and decreases during winter.
Q.10: Explain Isotherms
Ans: ISOTHERMS
Isotherms are the lines, which helps us know the horizontal distribution of temperature. These lines join the areas of same temperature on map. These lines are mostly parallel to latitude.
These lines are inclined towards equator in summer and inclined towards pools in winter. As compared to dry area the water area is large in southern hemisphere. These lines do not show any variation both in summer and winter because these lines remain parallel throughout the year.
CH: 5) ATMOSPHERIC PRESSURE & CIRCULATION
Q.1: Explain the difference between temperature and air pressure.
Ans: AIR PRESSURE
Atmosphere is made up of a number of gases. These gases press down on the Earth’s surface, exerting a force that we call atmospheric pressure or air pressure. Another word weight of air is Air pressure.
BAROMETER
Changes in air pressure are measured on an instrument called a barometer. Most barometers give a reading in millibars (mb for short). Readings over 1010 mb indicate high pressure. The measurement of air pressure is taken from seal-level. The pressure of air is not uniform on the surface of the earth.
ISOBARS
The lines, which join the regions having same air pressure, are known as Isobars.
AIR PRESSURE AND HEIGHT
Atmosphere extends to a large scale in height. Because of the heaviness of air the air pressure is large at the lower portion of atmosphere. This pressure decreases increasing heights. That is why, air pressure is more on seas and Lesson Mountains. The height of a mountain can be found if we know the air pressure on the peak and foot of mountain.
RELATIONSHIP BETWEEN TEMPERATURE AND A1R PRESSURE
Temperature and air pressure have relationship between them. Those areas where air pressure is low have high temperature and vice versa. Air spreads and expands on heating and air pressure decreases when it becomes light in weight. Air contracts when it is cooled. Due to contraction it becomes heavy. Due to heaviness of air its pressure increases. Few water vapours are in air, which are lighter than air. The quantity of Water vapours makes air light and air pressure decreases. According to principle, humid air is lighter than dry air and its pressure is also low.
Q.2: Explain Air Pressure Belt on Earth.
Ans: AIR PRESSURE BELTS ON THE GLOBE
The occurrences of air pressure on earth are described as following.
Equatorial Belt of low pressure
Sub-tropical belts of high pressure
Sub-polar belts of low pressure
Polar belts of high pressure
EQUATORIAL BELT OF LOW PRESSURE
This belt has very low air pressure. It is formed because ‘of heat at about 5 degrees on north south of both sides of equator. There is summer throughout the year in this belt. Air becomes high due to intense heat. It rises vertically upwards in the form of conventional currents. They also form a belt of low pressure here, known as belt of calms. Here, air rises upwards, so it cannot flow along the surface of the Earth. Due to this reason, atmosphere is calm here.
SUB-TROPICAL BELTS OF HIGH PRESSURE
At about latitude 30 degrees North and South occur the sub-tropical high pressure belts, sometimes known asthe “Horse Latitudes”, zones of calm and descending air currents. In the Southern Hemisphere, this belt is clearly defined but contains centers of high pressure termed as “pressure cells”.
The air from equator lifts upwards and moves towards poles on reaching a particular height. Due to its heaviness it moves downward towards the surface of the earth and air pressure increases in such regions. The air from upper regions is cold and dry, due to which these belts do not have rains.
SUB-POLAR BELTS OF LOW PRESSURE
Sub-polar belts of low pressure are formed when cold air collides with humid air and hot air rises upwards. When hot humid air currents from 30 degrees latitude north south and cold dry air current reach 60 degree latitude north-south, these air currents These belts are about 60 degrees latitude in North south strike against each other, and form the sub-polar belts of low pressure.
POLAR BELTS OF HIGH PRESSURE
These belts are on either sides in Polar Regions. The temperature remains below freezing point “throughout the year. As a result, belts of high pressure are formed, which are known as polar belts of high pressure.
Q.3: Explain Wind System
Ans: Wind System
The variation in atmospheric pressure causes winds. The earth moves over the surface of earth from areas of high pressure to areas of low pressure. These air currents are called winds.
PERMANENT WINDS
The winds which travels between the belts of air pressure all the year in the same are called as Permanent winds. These winds are of three types:
Eastern Winds
Eastern winds flows from sub tropical regions towards equator. These are permanent type of winds. These winds flow between 30-50 degree latitudes. These Wind are know as eastern as they come from east. These winds are also called trade winds because in olden times ships used these direction of eastern winds for their travel. These winds cause raini on the eastern coasts of continents.
Western Winds
Western winds flow from sub-tropical belts of high pressure to sub-polar belts of low pressure between 35-60 degree latitude. As they come towards west they are called as western winds. They travel in opposition direction of trade winds. These winds bring rains all the yearlong but there is more rain in winter than in summer.
iii. Polar Winds
Polar winds flow from the polar belts of high pressure to sub-polar belts of low pressure and between about 60 degrees latitude in either hemisphere. As these winds travel from east to west that is why these wind, are also known as Polar Eastern winds. In sub-northern hemisphere these winds flow from North-Eastern side to south western side and in sub southern hemisphere from south eastern side to southern-west. These wind travel from severe cold region to less cold region.
SEASONAL WINDS
The winds, which change their direction of blowing with the changing seasons, are called seasonal winds. They are also called temporary winds; an example of it is Monsoon wind winds.
Monsoon winds:
The entire surface winds, which change their directions with changing seasons, are called monsoon winds. These winds blow from sea to land in summer and from land to sea in winter. The reason of rainfall in summer in Pakistan due to Monsoon winds.
DIVISION OF MOONSON WINDS
Monsoon winds are divided into the following two types.
Summers Monsoon
During summer, the winds that blow from sea towards land are filled with water vapours. As a result, they bring heavy rains in eastern sides of continents. These winds are filled with humidity. In Pakistan, rainfall in summer is due to summer monsoon. They start from July to November .
Winter Monsoon
The temperature is low in lands during winter; therefore air pressure increases in lands. On the other hand, there is high temperature on Arabian Sea, which results into low pressure. Therefore, air blows from area of high pressure to area of low pressure. Being dry in nature, they cause no rain. Due to this reason, the Winter in Pakistan is dry and cold. However, rain in Balochistan is due to Western cyclone.
LOCAL WINDS
These winds blow due to local variation in the temperature and pressure, and influence a very small area. Local winds are specific and limited. Land breeze, Sea breeze, valley breeze and Mountain breeze are important local winds..
LAND AND SEA BREEZES
Land is heated more quickly than the adjacent sea during the day time. As a result, warm air rises over the land creating low pressure area there. However, there is prevailing high pressure over the adjacent sea.
As a result, the pressure causes the air to blow from the high pressure to the low pressure areas i.e. from the sea to the land. This is called sea breeze.
MOUNTAIN AND VALLEY EREEZES:
The slope and valley floors in the mountainous regions are more heated through insolation during daytime. Consequently, the warm air moves upslope. This upward moving breeze during daytime is called Valley Breeze.
Valley breezes reach mountain peaks and many a time yield precipitation. In the night, the upper part of the mountain cools quickly and starts falling down along the slope of the mountain. Air moves downward towards valley and is known as valley breeze.
Q.4: Explain types of cyclones
Ans: CYCLONE
The formation of whirlpool due to low air pressure and blows spirally is known as cyclones. When air moves upward due to heat, it reduces the high pressure air. Therefore, air moves from area of high presence to the area of low pressure, which makes cyclones. The surrounding of cyclones are prone to heavy clouds and severe rains. If a change occurs suddenly in air pressure of cyclone or distance among isobars reduces then severe rainfall occurs. These cyclones cause rainfalls in Baluchistan.
TYPES OF CYCLONE
Following are the types of cyclones.
TROPICAL CYCLONE
Tropical cyclones are formed on oceans. They are mostly formed in between 8-15 degree latitudes from in North South. They are disastrous in nature and destroy the areas in their way.
HURRICANE:
On the eastern coasts of Pacific Ocean, they are known as Hurricane. ‘
HARRY CYCLONES
Cyclones which are formed in Bay of Bengal and Bangladesh; these hurricanes have severe effects on India and cause disasters in coastal areas. They are known as Harry cyclones.
TEMPERATE CYCLONE
Temperate cyclones blow‘ rapidly from north to south between 40 to 70 degree latitude. They usually cover large areas. They ravel along western winds. When cold polar and a bit hot sub-polar wind collide with each other, temperate cyclones are formed. These collisions of winds make a polar front.
RORNADO’S
Tornado is a small cyclone. It covers a small area. In its .central part winds blow very fast spirally.
TRANDO’S STRUCTURE
In its centre there are heavy black cloud. It control part has humidity, dust and other material and nothing is visible. Tornadoes make disastrous in Northern America and some parts of Australia.
CH: 6) ATMOSPHEREIC HUMIDITY AND PRECEIPITATION
Q.1: Write a short note on Humidity and Condensation.
Ans: HUMIDITY AND CONDENSATION
HUMIDITY
Humidity is the amount of water vapours in the atmosphere.
CONDENSATION
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. The presence of Water in atmosphere is humidity. The quantity of w