Part-II

Question 1

Mass movements

Answer 1

1. Mass movement is also known as mass wasting.
2. It is the movement of masses of bodies of mud, bedrock, soil, and rock debris, which commonly happen along steep-sided hills and mountains because of the gravitational pull.
3. Gravity exerts its force on all matter, both bedrock and the products of weathering.
4. Hence, weathering is not essential for mass movement though it helps mass movements.
5. Mass movements which are sliding of huge amounts of soil and rock are seen in mudslides, landslides, and avalanches.
6. The air, water or ice does not transport debris with them from place to place but on the other hand the debris may transport with it water, ice or air.
7. These are very active over weathered slopes rather than over unweathered materials.
8. Mass movements do not come under erosion though there is a shift of materials from one place to another.
9. Heave, flow and slide are the three forms of movements.

Question 2

Causes preceding Mass movements

Answer 2

• There are many activating causes preceding mass movements. They are :

1. Removal of support from below to materials above through natural or artificial means.
2. An upsurge in height of slopes and gradient.
3. Overfilling through addition of materials by artificial filling or naturally.
4. Overburdening due to heavy rainfall, saturation, and lubrication of slope materials.
5. Elimination of material or load from over the original slope surfaces.
6. Event of explosions, earthquakes, etc.
7. Extreme natural seepage.
8. Heavy drawdown of water from reservoirs, lakes, and rivers leading to a slow outflow of water from under the slopes or river banks.
9. Indiscriminate removal of natural vegetation.

• Mass movements can be classified into two major classes:

1. Rapid movements
2. Slow movements

Question 3

Geomorphic processes

Answer 3

1. Geomorphological processes are natural mechanisms of erosion, weathering, and deposition that result in the alteration of the surficial materials and landforms at the surface of the earth.
2. The exogenic and endogenic forces cause chemical actions and physical pressures on earth materials
3. This brings about changes in the shape of the surface of the earth which are known as geomorphic processes.
4. Mass wasting, weathering, deposition, and erosion are exogenic geomorphic processes.
5. Volcanism and Diastrophism are endogenic geomorphic processes.
6. Any exogenic element of nature such that ice, water, and the wind that are capable of obtaining and carrying earth materials can be called a geomorphic agent.
7. When these elements of nature become portable due to gradients, they remove the materials and transport them over slopes and deposit them at a lower level.
8. The gravitational stresses are as vital as the other geomorphic processes.
9. Gravity is the force that is keeping us in contact with the surface and it is the force that switches on the movement of all surface material on earth.
10. It is the directional force stimulating all downslope movements of matter and it also causes stresses on the earth’s materials.
11. Indirect gravitational stresses stimulate tide and wave induced winds and currents.
12. Without gradients and gravity there would be no movement and therefore no transportation, erosion, and deposition are possible.
13. All the movements either on the surface of the earth or within the earth happen due to gradients —from high pressure to low pressure areas, from higher levels to lower levels, etc.

Question 4

Weathering

Answer 4

1. Weathering is the action of components of weather and climate materials over Earth.
2. There are several processes within weathering which act either independently or together to affect the materials of the earth in order to cut them to fragmental state.
3. This process causes the disintegration of rocks near the surface of the Earth.
4. It loosens and breaks down the surface minerals of rocks so they can be carried away by agents of erosion such as wind, water, and ice.
5. As very little or no motion of materials takes place in weathering, it is an in-situ or on-site process.
6. Flora and fauna life, water and atmosphere are the main reasons of weathering.
7. Weathering processes are determined by many climatic, topographic, vegetative factors and complex geological factors.
8. Climate has a significant role in weathering.
9. The weathering processes not only differ from climate to climate but also with the depth of the weathering mantle.
10. The degree of weathering that happens depends upon the resistance to weathering of the minerals in the rock and the degree of the biological, physical, and chemical stresses.
11. The minerals in rocks that are formed under high pressure and temperature inclined to be less resistant to weathering, whereas minerals formed at low pressure and temperature are more resistant to weathering.
12. Weathering denotes the process of wearing, breaking up, and fragmentation of the rock that creates the surface of the ground and that remains exposed to the weather.
13. The process results from forces of weather like rain action, variations in temperature and frost action.

Question 5

Three major groups of weathering processes

Answer 5

• There are three major groups of weathering processes:

1. Biological Weathering
2. Chemical Weathering
3. Physical or Mechanical Weathering
4. Biological weathering is the wearying and subsequent fragmentation of rocks by animals, plants, and microbes.
5. Physical or mechanical weathering is the weakening and consequent disintegration of rocks by physical forces.
6. Chemical weathering is the weakening and subsequent breakdown of rocks by chemical reactions.

Question 6

Significance of weathering to human life

Answer 6

1. Weathering is the initial stage in the formation of soil.
2. It produces other natural resources, for instance, clay which is used for making bricks.
3. Another significance is weathering weakens rocks making them easier for people to exploit, for example, by mining and quarrying
4. This process is accountable for the fragmentation of the rocks into smaller fragments and making the way for creation of not only soils and regolith, but also mass movements and erosion.
5. Biodiversity, and Biomes are basically a result of vegetation, and forests rely upon the depth of weathering mantles.
6. Erosion cannot be significant if the rocks are not weathered.
7. It means weathering aids erosion, mass wasting and reduction of relief and modifications in landforms are a result of erosion.
8. Weathering of rocks and deposits helps in the augmentation and concentrations of some valuable ores of manganese, aluminum, iron, and copper, etc. which have a great significance in the economy of the country.

Question 7

Enrichment

Answer 7

1. When rocks experience weathering, particular materials are removed through chemical or physical leaching by groundwater.
2. Thereby the congregation of leftover valuable materials increases.
3. Without weathering, the concentration of the same valuable material may not be adequate and economically feasible to exploit process and refine.
4. This is as called enrichment.

Question 8

Biological Weathering

Answer 8

1. Biological weathering only refers to weathering caused by plants, animals, fungi, and microorganisms such as bacteria.
2. It is contributed to or removal of ions and minerals from the weathering environment and physical variations due to movement or development of organisms.
3. It is also the wearying and subsequent fragmentation of rock by plants, animals, and microbes.

Question 9

Weathering by Microorganisms

Answer 9

1. Wedging and burrowing by organisms like termites, earthworms, rodents, etc. help in showing the new surfaces to chemical attack and helps in the penetration of air and moisture.
2. Bacteria, mosses, algae, and lichens frequently grow on rock surfaces, particularly in humid areas.
3. They form weak acids, which can convert some of the minerals to clay.
4. Algae growth can deteriorate several rock types and make it more exposed to weathering.

Question 10

Wethering by Humans

Answer 10

1. Humans also play an important role in biological weathering.
2. Construction activities like road building, mining also causes weathering.
3. Human beings by disturbing vegetation, ploughing and cultivating soils, also help in blending and producing new contacts between water, minerals, and air in the earth materials.

Question 11

Weathering by plants and animals

Answer 11

1. Decomposition of plant and animal help in the creation of carbonic acids, humic and other acids which boost decay and solubility of some elements.
2. Roots of plants exert tremendous pressure on the earth materials mechanically breaking them apart.

Question 12

Physical Weathering Processes

Answer 12

• Physical or mechanical weathering processes are influenced by some applied forces.
• The applied forces are:

1. Gravitational forces like shearing stress, load, and overburden pressure.
2. Expansion forces due to crystal growth, animal activity or temperature variations.
3. Water pressures regulated by drying and wetting cycles.

• Many of these forces are applied both at the surface and within different earth materials leading to rock breakage.
• Most of the physical weathering processes are caused by pressure release and thermal expansion.

Question 13

Weathering by Unloading and Expansion

Answer 13

1. Elimination of covering rock load because of sustained erosion causes vertical pressure release with the result that the upper layers of the rock enlarge producing fragmentation of rock masses.
2. Fractures will occur roughly parallel to the ground surface.
3. In areas of curved ground surface, arched fractures incline to create massive sheets or exfoliation slabs of rock.
4. Exfoliation sheets causing from expansion due to pressure release and unloading may measure hundreds or even thousands of metres in horizontal extent.
5. Big, smooth rounded domes are called exfoliation domes.

Question 14

Weathering by Temperature Changes and Expansion

Answer 14

1. Several minerals in rocks possess their own limits of contraction and expansion.
2. With an upsurge in temperature, all minerals enlarge and thrust against its neighbour and as temperature drops, a corresponding shrinkage takes place.
3. Due to diurnal changes in the temperatures, this internal movement among the mineral grains of the superficial layers of rocks takes place repeatedly.
4. This process is effective in high elevations and arid climates where diurnal temperature variations are extreme.

Question 15

Weathering by Freezing, Thawing and Frost Wedging

Answer 15

1. Frost weathering happens due to development of ice within openings and cracks of rocks during recurrent cycles of melting and freezing.
2. This process is effective at high elevations in mid-latitudes where melting and freezing is frequently recurrent.
3. Glacial regions are subject to frost wedging every day.
4. In this course, the rate of freezing is significant.
5. Hasty freezing of water causes its high pressure and rapid expansion.
6. The resulting expansion affects joints, cracks and small intergranular fractures to become wider and wider till the rock breaks apart.

Question 16

Salt Weathering

Answer 16

1. Salt crystallisation is most effective of all salt-weathering processes.
2. Salts in rocks enlarge due to hydration, crystallisation and thermal action.
3. Various salts like sodium, barium, calcium, potassium, and magnesium, have an inclination to enlarge.
4. Enlargement of these salts relies on temperature and their thermal properties.
5. High-temperature ranges between 30 and 50 degrees Celsius of surface temperatures in deserts support such salt expansion.
6. Salt crystals in the adjacent surface pores cause splitting of single grains within rocks, which ultimately drop.
7. This process of dropping of individual grains may result in granular disintegration or granular foliation.

Question 17

Chemical Weathering

Answer 17

1. A cluster of weathering processes namely solution, carbonation, hydration, oxidation, and reduction.
2. These processes act on rocks to decompose, dissolve or moderate them to a fine clastic state through chemical reactions by oxygen, surface/ soil water, and other acids.
3. Water and air along with heat must be present to speed up all chemical reactions.

Question 18

Weathering by Solution

Answer 18

1. When substances are dissolved in acids or water, then the water or acid with dissolved substances is called a solution.
2. This process includes the removal of solids in solution and depends upon the solubility of a mineral in weak acids or water.
3. Many solids disintegrate and mix up as a suspension in water as they come in contact with water.
4. Some of the soluble rock-forming minerals like sulphates, nitrates, and potassium, etc. are affected by this process.
5. Hence, these minerals are simply leached out without leaving any remains in rainy climates and accumulate in dry regions.
6. Minerals like calcium magnesium bicarbonate and calcium carbonate present in limestone are soluble in water containing carbonic acid and are transported away in water as a solution.
7. Carbon dioxide formed by decomposing organic matter along with soil water significantly assists in this reaction.
8. Sodium chloride is also a rock-forming mineral and is vulnerable to this process of solution.
9. Carbonation, oxidation and Hydration go hand in hand and accelerate the weathering process.

Question 19

Weathering by Carbonation

Answer 19

1. Carbonation is the reaction of bicarbonate and carbonate with minerals.
2. It is a general process helping the fragmentation of feldspars and carbonate minerals.
3. Carbon dioxide from the soil and atmospheric air is absorbed by water to form carbonic acid that acts like weak acid.
4. Magnesium carbonates and Calcium carbonates are dissolved in carbonic acid.
5. These are removed in a solution without leaving any residue resulting in cave formation.

Question 20

Weathering by Hydration

Answer 20

1. Hydration is the chemical addition of water.
2. Minerals take up water and enlarge.
3. This enlargement causes an increase in the volume of the material itself or rock.
4. This process is long and reversible, sustained recurrence of this process causes fatigue in the rocks.
5. This may lead to their disintegration of rocks.

Question 21

Weathering by Oxidation and Reduction

Answer 21

1. In weathering, oxidation denotes a mixture of a mineral with oxygen to form hydroxides or oxides.
2. Oxidation happens where there is ready access to the oxygenated waters and atmosphere.
3. The minerals commonly involved in this process are manganese, sulphur, iron, etc.
4. In the process of oxidation, rock fragmentation happens due to the disturbance caused by adding of oxygen.
5. Red colour of iron upon oxidation turns to yellow or brown.
6. When oxidised minerals are positioned in a situation where oxygen is absent, reduction occurs.
7. Such circumstances exist commonly below the water table, waterlogged ground and in areas of stagnant water.
8. Red colour of iron upon reduction turns to greenish or bluish grey.
9. These weathering processes are interconnected.

Question 22

Weathering by Exogenic processes

Answer 22

1. The exogenic processes obtain their energy from the gradients generated by tectonic factors, processes, their corresponding driving forces and atmosphere determined by the energy from the sun.
2. Precipitation and temperature are the two significant climatic components that regulate different processes.
3. Whole exogenic geomorphic processes are covered under a common term, denudation which means to uncover.
4. Weathering, transportation, and erosion are comprised in denudation.
5. Gravitational force acts upon every material on earth having a sloping surface and incline to create the movement of matter in downward slope direction.

Question 23

Weathering by Stress

Answer 23

1. Force applied per unit area is called stress.
2. Stress is created in a solid by pulling or pushing and this induces deformation.
3. Forces acting along the surfaces of earth materials are shear stresses and it breaks rocks and other earth materials.
4. The shear stresses result in slippage or angular displacement.
5. Besides gravitational stress, earth materials become exposed to molecular stresses that may be caused by several factors amongst which crystallisation, melting, and temperature variations are the most usual.
6. Chemical processes generally lead to loosening of bonds between grains, dissolving of soluble minerals or strengthening materials.
7. Therefore, the fundamental cause that leads to erosion, mass movements, and weathering is the development of stresses in the body of the earth materials.
8. The effects of most of the exogenic geomorphic processes are minor and slow.
9. It may be imperceptible in a short time span, but will in the long run influence the rocks harshly due to constant fatigue.

Question 24

Weathering by Endogenic Processes

Answer 24

1. The energy originating from within the earth is the main force behind endogenic geomorphic processes.
2. This energy is mostly produced by rotational and tidal friction, radioactivity, and primordial heat from the origin of the earth.
3. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere.
4. Due to differences in geothermal gradients and heat flow from within, strength and crustal thickness, the action of endogenic forces are uneven.
5. Therefore the tectonically regulated original crustal surface is not uniform.

Question 25

Weathering by Diastrophism

Answer 25

• All processes that move, lift or build up portions of the crust of Earth come under diastrophism.
• They include:

1. Orogenic Processes:

• It includes mountain building through severe folding and faulting affecting long and narrow belts of the crust of Earth.
• Orogeny is a mountain building process.

1. Epeirogenic processes:

• It involves the uplift or warping of large parts of the crust of the earth.
• Epeirogeny is a continental building process.

1. Earthquakes comprising local, comparatively minor movements.
2. Plate tectonics comprising horizontal movements of crustal plates.

• Through the processes of epeirogeny, orogeny, earthquakes and plate tectonics, there can be fracturing and faulting of the crust.
• Each of these courses causes pressure, volume and temperature (PVT) changes which in turn induce metamorphism of rocks.

Question 26

Volcanism

Answer 26

Volcanism comprises the movement of magma onto or toward the surface of the earth and also the creation of several extrusive and intrusive volcanic forms.

Question 27

Factors Controlling Temperature Distribution

Answer 27

• The temperature of air at every place is influenced by :

1. The latitude of the place
2. The altitude of the place
3. Distance from the sea
4. The air- mass circulation
5. The presence of warm and cold ocean currents
6. Local aspects

Question 28

The latitude effect on Temperature Distribution

Answer 28

1. The temperature of a place is determined by the insolation received.
2. The insolation differs according to the latitude, therefore, the temperature also differs consequently.

Question 29

The altitude effect on Temperature Distribution

Answer 29

1. The atmosphere is indirectly heated by terrestrial radiation.
2. Therefore, the places adjacent to the sea-level record higher temperatures than the places located at higher elevations.
3. The temperature usually decreases with increasing height.
4. The rate of decrease of temperature with height is called as the normal lapse rate.

Question 30

Distance from the sea and its effect on Temperature Distribution

Answer 30

1. The main factor that influences the temperature is the position of a place with respect to the sea.
2. The sea gets heated slowly and loses heat slowly compared to land.
3. Land heats up and cools down rapidly.
4. So, the difference in temperature over the sea is less compared to the terrestrial surface.
5. The places located near the sea come under the moderating influence of the sea and land breezes which regulate the temperature.

Question 31

Air-mass and Ocean currents effect on Temperature Distribution

Answer 31

1. The passage of air masses also affects the temperature like the land and sea breezes.
2. The places which come under the effect of warm air-masses experience higher temperature and the places that come under the influence of cold air- masses experience lower temperature.
3. Likewise, the places situated on the coast where the warm ocean currents flow record higher temperature than the places situated on the coast where the cold currents flow.

Question 32

Composition of the atmosphere

Answer 32

1. The atmosphere is comprised of several gases, dust particles, and water vapour.
2. The presence of oxygen becomes insignificant at the height of 120 km from the surface of the earth with respect to the composition of the atmosphere.
3. Water vapour and Carbon dioxide occur only up to 90 km.

Question 33

Ozone gas

Answer 33

1. Present around 10-50 km above earth surface and acts as a sieve, absorbing UV (ultraviolet rays) from the sun.
2. Ozone averts the harmful rays from reaching the surface of the earth.

Question 34

Water vapour

Answer 34

1. Water vapour is a variable gas, declines with altitude.
2. It also drops towards the poles from the equator.
3. It acts like blanket letting the earth to neither to become too hot nor too cold.
4. It also contributes to the stability and instability in the air.

Question 35

Dust particles

Answer 35

1. Dust particles are in higher concentration in temperate and subtropical regions due to dry winds in contrast to the Polar Regions and equatorial regions.
2. They act as hygroscopic nuclei over which water vapour of atmosphere condenses to create clouds.

Question 36

Nitrogen

Answer 36

1. The atmosphere is composed of 78% nitrogen.
2. Nitrogen cannot be used directly from the air.
3. Biotic things need nitrogen to make proteins.
4. The Nitrogen Cycle is the way of supplying required nitrogen for living things.

Question 37

Oxygen

Answer 37

1. The atmosphere is composed of 21% oxygen.
2. It is used by all living things and is essential for respiration.
3. It is obligatory for burning.

Question 38

Argon

Answer 38

1. The atmosphere is composed of 0.9% argon.
2. They are mainly used in light bulbs.

Question 39

Carbon Dioxide

Answer 39

1. The atmosphere is composed of 0.03% carbon dioxide.
2. Plants use it to make oxygen.
3. It is significant as it is opaque to outgoing terrestrial radiation and transparent to incoming solar radiation.
4. It is also blameable for the greenhouse effect.

Question 40

Structure of Atmosphere

Answer 40

• There are five layers in the structure of atmosphere depending upon temperature.
• These layers are:

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Ionosphere
6. Exosphere

Question 41

Troposphere

Answer 41

1. It is considered as the lowest layer of Earth’s atmosphere.
2. The troposphere starts at surface of the earth and goes up to a height of 7 to 20 km.
3. All weather occurs within this layer.
4. This layer has water vapour and mature particles.
5. Temperature decreases at the rate of 1 degree Celsius for every 165 m of height.
6. Tropopause separates Troposphere and Stratosphere.

Question 42

Stratosphere

Answer 42

1. It is the second layer of the atmosphere found above the troposphere.
2. It extends up to 50 km of height.
3. This layer is very dry as it contains little water vapour.
4. This layer provides some advantages for flight because it is above stormy weather and has steady, strong, horizontal winds.
5. The ozone layer is found in this layer.
6. The ozone layer absorbs UV rays and safeguards earth from harmful radiation.
7. Stratopause separates Stratosphere and Mesosphere.

Question 43

Mesosphere

Answer 43

1. The Mesosphere is found above the stratosphere.
2. It is the coldest of the atmospheric layers.
3. The mesosphere starts at 50 km above the surface of Earth and goes up to 85 km.
4. The temperature drops with altitude in this layer.
5. By 80 km it reaches -100 degrees Celsius.
6. Meteors burn up in this layer.
7. The upper limit is called Mesopause which separate Mesosphere and Thermosphere.

Question 44

Thermosphere

Answer 44

1. This layer is found above Mesopause from 80 to 400 km.
2. Radio waves which are transmitted from the earth are reflected back by this layer.
3. The temperature increases with height.
4. Aurora and satellites occur in this layer.

Question 45

Ionosphere

Answer 45

1. The lower Thermosphere is called the Ionosphere.
2. Ionosphere consists of electrically charged particles known as ions.
3. This layer is defined as the layer of the atmosphere of Earth that is ionized by cosmic and solar radiation.
4. It is positioned between 80 and 400 km above the Mesopause.

Question 46

Exosphere

Answer 46

1. It is the outermost layer of the atmosphere.
2. The zone where molecules and atoms escape into space is mentioned as the exosphere.
3. It extends from the top of the thermosphere up to 10,000 km.

Question 47

General circulation of the Atmosphere

Answer 47

The pattern of the movement of the planetary winds is called general circulation of the atmosphere.

Question 48

Factors for General Circulation of the Atmosphere

Answer 48

1. The pattern of planetary winds largely depends on:

• Latitudinal variation of atmospheric heating
• The emergence of pressure belts
• The migration of belts following the apparent path of the sun
• The distribution of continents and oceans
• The rotation of the earth

1. The general circulation of the atmosphere also sets in motion the marine water circulation which affects the climate of the Earth.
2. The air at the ITCZ (Inter Tropical Convergence Zone) upsurges because of convection caused by high insolation and low pressure is generated.
3. The winds from the tropics join at this low-pressure zone.
4. The joined air upsurges along with the convective cell.
5. It reaches the top of the troposphere up to an altitude of 14 km.
6. It further moves toward the poles. This causes accumulation of air at about 30o North and South.
7. Another reason for sinking is the cooling of air when it reaches 30 degrees North and South latitudes.
8. Downward near the land surface, the air flows towards the equator as the easterlies.
9. The easterlies from either side of the equator converge in the Inter-Tropical Convergence Zone (ITCZ).
10. Such circulations from the surface up and vice-versa are called cells.
11. This type of a cell in the tropics is called Hadley Cell.
12. In the mid-latitudes, the circulation is that of dipping cold air that comes from the poles and the mounting warm air that blows from the subtropical high.
13. At the surface, these winds are called westerlies and the cell is known as the Ferrel cell.
14. At polar latitudes, the cold dense air subsides near the poles and blows towards middle latitudes as the polar easterlies. This cell is called the polar cell.
15. These Ferrel cells, Hadley Cell, and polar cell set the configuration for the general circulation of the atmosphere.

Question 49

General Atmospheric Circulation and its Effects on Oceans

Answer 49

1. The general circulation of the atmosphere also influences the oceans.
2. Warming and cooling of the Pacific Ocean is most significant in terms of general atmospheric circulation.
3. The warm water of the central Pacific Ocean gradually drifts towards the South American coast and substitutes the cool Peruvian current.
4. Such presence of warm water off the coast of Peru is known as the El Nino.
5. The El Nino is associated with the pressure variations in Australia and Central Pacific.
6. This variation in pressure condition over the Pacific is known as the southern oscillation.
7. The combined phenomenon of El Nino and southern oscillation is known as ENSO.

Question 50

Heating and Cooling of atmosphere

Answer 50

1. There are various ways of heating and cooling of the atmosphere.
2. The earth after being warmed by insolation transfers the heat to the atmospheric layers in long waveform.

Question 51

Conduction

Answer 51

1. The air in interaction with the land gets heated gradually and the upper layers in touch with the lower layers also get heated. This process is called conduction.
2. This process takes place when two bodies of uneven temperature are in contact with one another, there is a flow of energy from the warmer to the cooler body.
3. The heat transfer continues until both the bodies reach the same temperature or the contact is interrupted.
4. This process is significant in heating the lower layers of the atmosphere.

Question 52

Convection

Answer 52

1. The air in contact with the earth upsurges vertically on heating in the form of currents and transfers the heat of the atmosphere.
2. This vertical heating of the atmosphere is known as convection.
3. The convective transfer of energy is limited only to the troposphere.

Question 53

Advection

Answer 53

1. The transfer of heat through horizontal movement of air is called advection.
2. Horizontal movement of the air is comparatively more significant than the vertical movement.
3. Most of the diurnal variation in weather is caused by advection only in the middle latitudes.
4. During summer in tropical regions predominantly in Northern India, local winds called ‘loo’ is the result of advection process.

Question 54

Atmospheric pressure

Answer 54

1. The weight of a column of air contained in a unit area from the mean sea level to the top of the atmosphere is called the atmospheric pressure.
2. It is measured in force per unit area.
3. It is expressed in ‘milibar’ or mb unit.
4. In application level, the atmospheric pressure is stated in kilo-pascals.
5. It is measured by the aneroid barometer or mercury barometer.
6. In lower atmosphere, pressure declines rapidly with height.
7. The vertical pressure gradient force is much larger than that of the horizontal pressure gradient and is commonly balanced by an almost equal but opposite gravitational force.
8. Low-pressure system is encircled by one or more isobars with the lowest pressure at centre.
9. High pressure system is also encircled by one or more isobars with highest pressure in centre.
10. Isobars are lines connecting places having equal pressure.

Question 55

Pressure Gradient

Answer 55

The rate of change of pressure in regard to distance is the pressure gradient.

Question 56

Pressure belts

Answer 56

1. There is a pattern of alternate high and low-pressure belts over the earth.
2. There are seven pressure belts.
3. Except the Equatorial low, there are two Sub-Tropical highs (in North and South), the two Sub-polar lows (in North and South), and the two Polar highs (in North and South).
4. The above-given pressure belts oscillate with the movement of the sun.
5. In the northern hemisphere, they move southwards in winter, and in summers they move northwards.
6. The Equatorial region gets abundant heat and warm air being light, the air at the Equator rises, generating a low pressure.
7. Equatorial low

• It is found near the equator.
• The sea level pressure is low.

1. Subtropical high
   * The region in 30 degrees North and 30 degrees South, which are high-pressure areas.
2. Sub-polar Lows
   * The region in 60 degrees North and 60 degrees South, which are low-pressure belts.
3. Polar Highs
   * These occur near poles which have high pressure.

Question 57

Tropical Cyclones

Answer 57

1. Tropical cyclones are regarded as one of the most devastating natural calamities in the world.
2. They originate and intensify over warm tropical oceans.
3. These are ferocious storms that originate over oceans in tropical areas and move over to the coastal areas causing violent winds, very heavy rainfall, and storm outpourings.

Question 58

Names of cyclone in different regions

Answer 58

• They are known as:

1. Cyclones in the Indian Ocean
2. Hurricanes in the Atlantic
3. Typhoons in the Western Pacific and the South China Sea
4. Willy-willies in Western Australia

Question 59

Conditions for the formation of Tropical Cyclone

Answer 59

• The conditions which favour the formation and intensification of tropical cyclone storms are:

1. Large sea surface with a temperature higher than 27° C
2. Presence of the Coriolis force
3. Small differences in the vertical wind speed
4. A pre-existing weak- low-pressure area or low-level-cyclonic circulation
5. Upper divergence above the sea level system

Question 60

Formation of Cyclone

Answer 60

1. The energy that strengthens the storm comes from the condensation process in the towering cumulonimbus clouds, surrounding the centre of the storm.
2. With an uninterrupted supply of moisture from the sea, the storm is again strengthened.
3. On reaching the terrestrial region the moisture supply is cut off and the storm dissipates.
4. The place where a tropical cyclone cuts the coast is called the landfall of the cyclone.
5. A landfall is frequently accompanied by sturdy winds, heavy rain and mounting sea waves that could threaten people and cause damage to properties.
6. Cyclones which cross 20 degrees North latitude are more destructive.
7. They cover a larger area and can originate over the land and sea whereas the tropical cyclones originate only over the seas and on reaching the land they dissipate.

Question 61

Eye of Cyclone

Answer 61

1. A mature tropical cyclone is characterised by the strong spirally circulating wind around the centre which is called the eye.
2. The eye is an area with calm weather descending air.
3. It is characterized by light winds and clear skies.

Question 62

Eye Wall (Cyclones)

Answer 62

1. Around the eye is the eyewall, where there is a strong spiralling rise of air to a greater height reaching the tropopause.
2. The wind reaches maximum velocity in this region and torrential rain occurs here.
3. From the eyewall, rain bands may radiate and trains of cumulus and cumulonimbus clouds may drift into the outer region.

Question 63

Extra-Tropical Cyclones

Answer 63

1. The Extra-Tropical Cyclones are storm systems emerging in the mid and high latitudes, away from the tropics.
2. They are low-pressure systems with associated cold fronts, warm fronts, and occluded fronts.
3. These cyclones are formed along the polar front.
4. These cyclones move from west to east but tropical cyclones, move from east to west.
5. In the beginning, the front is stationary.
6. Extra-tropical cyclones are also known as mid-latitude storms or baroclinic storms.
7. In the Northern hemisphere, cold air blows from the north of the front and warm air blows from the south.
8. When the pressure descents along the front, the cold air move towards the south and the warm air moves northwards setting in motion an anticlockwise cyclonic circulation.
9. The cyclonic circulation results in a well-built extratropical cyclone, with a cold front and a warm front.
10. There are pockets of warm air compressed between the forward and the rear cold air.
11. The warm air climbs over the cold air and a series of clouds appear over the sky ahead of the warm front and cause rainfall.
12. The cold front approaches the warm air from behind and pushes the warm air up.
13. As an outcome, cumulus clouds develop along the cold front.
14. The cold front moves faster than the warm front eventually surpassing the warm front.
15. The warm air is entirely lifted up and the front is occluded and the cyclone dissipates.
16. They can originate over the land and sea and cover a larger area.
17. This cyclone affects a much larger area as compared to the tropical cyclone.
18. The velocity of wind in a tropical cyclone is much higher and it is more damaging.

Question 64

Rock Cycle

Answer 64

1. The rock cycle is a basic concept in geology that defines the laborious transitions through geologic time among the three main rock types:

• Igneous rocks
• Sedimentary rocks
• Metamorphic rocks

1. Rocks do not remain in their original form for a long period as they undergo a transformation.
2. This cycle is an uninterrupted process through which old rocks are converted into new ones.
3. Igneous rocks are primary rocks.
4. These rocks can be changed into metamorphic rocks.
5. Sedimentary and metamorphic rocks form from these primary rocks.
6. The fragments evolved out of metamorphic rocks and igneous again form into sedimentary rocks.
7. Sedimentary rocks themselves can develop into fragments.
8. The crustal rocks -igneous, metamorphic and sedimentary-once formed may be carried down into the interior of the earth through subduction.
9. In this process, parts or entire crustal plates subduct under another plate and the same melt at high temperature in the interior.
10. This results in the formation of molten magma, the unique source for igneous rocks.

Question 65

The Processes of the Rock Cycle

Answer 65

1. The rock cycle encompasses several processes.
2. The key processes of the rock cycle are:

• Crystallization
• Erosion and sedimentation
• Metamorphism

Question 66

Forces that drive the rock cycle

Answer 66

1. Plate tectonics
2. Spreading ridges
3. Subduction zones
4. Continental collision
5. Accelerated erosion
6. Water

Question 67

Forces Affecting the Velocity and Direction of Wind

Answer 67

1. The air in motion is called wind.
2. The wind blows from high pressure to low pressure.
3. The wind at the surface experiences friction.
4. The rotation of the earth also affects the wind movement.
5. The force exerted by the rotation of the earth is known as the Coriolis force.
6. Therefore, the horizontal winds near the Earth’s surface respond to the combined effect of three forces:

• The Pressure Gradient Force
• The Frictional Force
• The Coriolis Force

Question 68

Pressure Gradient Force (Wind)

Answer 68

1. The differences in atmospheric pressure generate a force.
2. The rate of change of pressure with regard to distance is known as the pressure gradient.
3. The pressure gradient is weak where the isobars are distant and strong where the isobars are close by to each other.

Question 69

Frictional Force (Wind)

Answer 69

1. It impacts the speed of the wind.
2. The friction is maximum at the surface and minimal over the sea surface.
3. The influence of frictional force usually stretches up to an elevation of 1 – 3 km.

Question 70

Coriolis force

Answer 70

1. The rotation of the earth about its axis affects the direction of the wind and this force is called the Coriolis force.
2. It is directly proportional to the angle of latitude.
3. It deflects the wind to the left direction in the southern hemisphere and the right direction in the northern hemisphere.
4. The deflection is more when the wind velocity is high.
5. It is maximum at the poles and is absent at the equator.
6. The force acts perpendicular to the pressure gradient force.
7. The pressure gradient force is perpendicular to an isobar.
8. The higher the pressure gradient force, the more is the speed of the wind and the larger is the deflection in the direction of wind happens.
9. As a result of these two forces functioning perpendicular to each other, in the low-pressure areas the wind blows around it.
10. The Coriolis force is zero at the equator and the wind blows perpendicular to the isobars.

Question 71

Nitrogen

Answer 71

1. Nitrogen is a chief constituent of the bodies of living organisms as the Nitrogen atoms are found in all proteins and DNA
2. It is a common limiting nutrient in nature and agriculture.
3. It exists in the atmosphere as N2
4. Usually, nitrogen is usable only after it is fixed.
5. Nitrogen fixation is a process where bacteria convert N2 into ammonia, a form of nitrogen usable by plants.
6. Only a few types of organisms like and blue-green algae and certain species of soil bacteria are skilful of consuming nitrogen directly in its gaseous form.
7. When animals eat the plants, they obtain usable nitrogen compounds.
8. A limiting nutrient is a nutrient that’s in shortest supply and limits growth.
9. When fertilizers comprising phosphorous and nitrogen are transported in a runoff to rivers and lakes, they can result in blooms of algae. This is called eutrophication.

Question 72

The Nitrogen Cycle

Answer 72

1. The nitrogen cycle is the biogeochemical cycle.
2. Nitrogen is a main constituent of the atmosphere encompassing about 75% of the atmospheric gases.
3. It is also a vital constituent of different organic compounds such as the vitamins, nucleic acids, pigments, amino acids, and proteins.
4. The major source of free nitrogen is the action of soil micro-organisms and associated plant roots on atmospheric nitrogen found in pore spaces of the soil.

Fixation

1. Fixation is the primary step in the process of converting nitrogen, usable by plants.
2. Normally, bacteria change nitrogen into ammonium.

Nitrification

1. This is the process by which ammonium converted into nitrates by bacteria.
2. The plants absorb these Nitrates.

Assimilation

1. Through assimilation only plants get nitrogen.
2. They absorb nitrates from the soil into their roots.
3. Then nitrogen gets used in chlorophyll, nucleic acids, and amino acids.

Ammonification

1. This is part of the decaying process.
2. When a plant or animal expires, decomposers such that bacteria and fungi turn the nitrogen back into ammonium so it can go back into the nitrogen cycle.

De-nitrification

1. Surplus nitrogen in the soil gets put back out into the air.
2. There are special bacteria that execute this job as well.

Question 73

Oxygen

Answer 73

1. Oxygen is regarded as the vital element in Earth.
2. It is the most common element of the human body.
3. Oxygen constitutes about 65% of the mass of the human body and most of this is in the form of water.
4. Oxygen also makes up about 30% of the Earth and 20% of the atmosphere.

Question 74

Processes that consume Oxygen

Answer 74

Breathing

1. All flora and fauna consume oxygen when they breathe.
2. They breathe in oxygen and breathe out carbon dioxide.

Decomposing

1. When flora and fauna die, they decay. During this process, the oxygen is absorbed and carbon dioxide is discharged.

Rusting

1. Rusting is also known as oxidation in which iron turns into iron oxide.
2. When iron things rust they absorb oxygen.

Combustion

1. Without oxygen, it is hard to ignite.
2. When things burn, they consume oxygen and discharges it with carbon dioxide.

Question 75

Processes That Produce Oxygen

Answer 75

Photosynthesis

1. The green plants use sunlight to produce nutrients from carbon dioxide and water.
2. Photosynthesis in plants usually comprises the chlorophyll and produces oxygen as a by-product.

Sunlight

1. Some oxygen is produced when sunlight reacts with water vapor in the atmosphere.
2. It is involved in the oxidation of carbohydrates with the release of energy, carbon dioxide, and water.

Question 76

Oxygen Cycle

Answer 76

1. The oxygen cycle is the biogeochemical cycle of oxygen.
2. The cycling of oxygen is a highly complex process.
3. Oxygen occurs in several combinations and chemical forms.
4. It combines with nitrogen to form nitrates.
5. It also combines with several other elements and minerals to form different oxides such as the iron oxide, aluminium oxide and others.
6. The carbon dioxide is absorbed by plants during photosynthesis.
7. A considerable amount of oxygen is produced from the decomposition of water molecules by sunlight during photosynthesis.
8. Respiration by humans and animal consumes oxygen and releases carbon dioxide into the atmosphere.
9. Again this carbon dioxide is again, taken up by plants, for photosynthesis and the process repeat.

Question 77

Carbon

Answer 77

1. Carbon is the fourth most abundant element in the universe and is absolutely essential to life on Earth.
2. It is the basic element of all living organisms which are made of carbon.
3. It is also a part of the ocean, air, and even rocks.
4. Because the Earth is a dynamic place, carbon does not stay still.

Question 78

The Carbon Cycle

Answer 78

1. The carbon cycle is chiefly the conversion of carbon dioxide.
2. It is the biogeochemical cycle by which carbon is interchanged among the biosphere, hydrosphere, atmosphere, and geosphere of the Earth.
3. Plants use carbon dioxide and sunlight to make their own food and grow.
4. The conversion of carbon dioxide is started by the fixation of carbon dioxide through photosynthesis from the atmosphere.
5. Such conversion results in the creation of carbohydrate, glucose that may be transformed to other organic compounds like starch, sucrose, cellulose, etc.
6. In this process, more carbon dioxide is generated and discharged through its roots or leaves during the day.
7. The leftover carbohydrates become part of the plant tissue.
8. Plant tissues are eaten by the herbivorous animals.
9. The carbon becomes part of the plant.
10. Plants that perish and are buried will turn into fossil fuels made of carbon like coal and oil over millions of years.
11. Most of the carbon quickly enters the atmosphere as carbon dioxide while burning the fossil fuels.
12. Carbon dioxide is a greenhouse gas and traps heat in the atmosphere.
13. Earth would be a frozen world without Carbon dioxide and other greenhouse gases.

Question 79

Biogeochemical Cycles

Answer 79

1. Biological Chemical + Geological Process= Biogeochemical
2. Energy flows through an ecosystem and is released as heat, but chemical elements are recycled.
3. The ways in which an element or compound moves between its several biotic and abiotic forms and locations in the biosphere is called a biogeochemical cycle.
4. It is a movement of nutrients and other elements between living and non-living beings.
5. The sun is the basic source of energy on which all life depends.
6. Life on earth comprises a great variety of living organisms.
7. These living organisms exist and survive in a diversity of associations. Such survival encompasses the presence of systemic flows such as flows of energy, water, and nutrients.
8. The balance of the chemical elements is maintained by a cyclic movement through the tissues of plants and animals.
9. The cycle starts by absorbing the chemical elements by the organism and is returned to the air, water, and soil through decomposition.
10. These cycles are largely energized by solar insolation.
11. There are two types of biogeochemical cycles:

• The gaseous cycle
• In the gaseous cycle, the main reservoir of nutrients is the atmosphere and the ocean.
• The sedimentary cycle
• In the sedimentary cycle, the main reservoir is the soil and the sedimentary and other rocks of the earth’s crust.

Question 80

Types of Biogeochemical Cycles

Answer 80

• The important biogeochemical cycles are:

1. The Carbon Cycle
2. The Nitrogen Cycle
3. The Oxygen Cycle
4. The Phosphorus Cycle
5. The Sulphur Cycle
6. The Water Cycle/ Hydrological Cycle
7. The Rock Cycle

Question 81

Salinity of ocean waters

Answer 81

1. Salinity means the total content of dissolved salts in Sea or Ocean.
2. Salinity is calculated as the amount of salt dissolved in 1,000 gm of seawater.
3. It is generally expressed as ‘parts per thousand’ (ppt).
4. A salinity of 24.7 % has been regarded as the upper limit to fix ‘brackish water’.
5. It is a significant factor in deciding several characteristics of the chemistry of natural waters and of biological processes.

Question 82

Factors affecting ocean salinity

Answer 82

1. Salinity, temperature, and density of water are interconnected. The salinity of water in the surface layer of oceans is influenced by:

• Evaporation
• Precipitation

1. In the coastal regions, the surface salinity is influenced by the freshwater flow from rivers.
2. In the Polar region, the surface salinity is influenced by the processes of freezing and melting of ice.
3. The wind also influences the salinity of an area by moving water to other areas.
4. The ocean currents contribute to the salinity variations.
5. The change in the density or temperature influences the salinity of water in an area.

Question 83

Highest salinity in water bodies

Answer 83

1. Lake Van in Turkey- 330 o/oo
2. Dead Sea- 238 o/oo
3. Great Salt Lake- 220 o/oo

Question 84

Dissolved Salts in Sea Water (gm of Salt per kg of Water)

Answer 84

1. Chlorine- 18.97
2. Sodium- 10.47
3. Sulphate- 2.65
4. Magnesium- 1.28
5. Calcium- 0.41
6. Potassium- 0.38
7. Bicarbonate- 0.14
8. Bromine- 0.06
9. Borate- 0.02
10. Strontium- 0.01

Question 85

Share of different salts

Answer 85

1. Sodium chloride — 77.7%
2. Magnesium chloride—10.9%
3. Magnesium sulphate —.4.7%
4. Calcium sulphate — 3.6%
5. Potassium sulphate — 2.5%

Question 86

Horizontal Distribution of Salinity

Answer 86

1. The salinity for normal Open Ocean ranges between 33o/oo and 37 o/oo.
2. The highest salinity is recorded between 15° and 20° latitudes.
3. Maximum salinity (37 o/oo) is observed between 20° N and 30° N and 20° W – 60° W.
4. The salinity gradually decreases towards the north.
5. The salinity sometimes reaches up to 70 o/oo in the hot and dry regions where evaporation is high.
6. The salinity variation in the Pacific Ocean is largely due to its shape and larger areal stretch.
7. In the landlocked Red Sea, the salinity is 41o/oo which considerably high.
8. The salinity in the estuaries and the Arctic varies from 0 – 35 o/oo , seasonally.
9. Due to the influx of melted water from the Arctic region, the salinity decreases from 35 o/oo – 31 o/oo on the western parts of the northern hemisphere.
10. The North Sea records higher salinity due to more saline water brought by the North Atlantic Drift despite its location in higher latitudes.
11. Due to the influx of river waters in the large amount, the Baltic Sea records low salinity.
12. The Mediterranean Sea accounts for the higher salinity due to high evaporation.
13. Salinity is very low in the Black Sea due to massive freshwater influx by rivers.
14. The average salinity of the Indian Ocean is 35 o/oo.
15. The low salinity trend in the Bay of Bengal is due to the influx of river water.
16. But the Arabian Sea displays higher salinity due to the low influx of fresh water and high evaporation.

Question 87

Vertical Distribution of Salinity

Answer 87

1. Salinity changes with depth, but the way it changes relies on the position of the sea.
2. Salinity at the surface of the sea is decreased by the input of fresh waters or increased by the loss of water to ice or evaporation.
3. Salinity at depth is fixed as neither water nor salt can be added in it.
4. There is a marked difference in the salinity between the surface zones and the deep zones of the oceans.
5. The lower saline water remains above the higher saline dense water.
6. Salinity, usually, increases with depth and there is a distinct zone called the halocline, where salinity increases abruptly.
7. The increasing salinity of seawater causes an increase in the density of water.
8. High salinity seawater, usually, sinks below the lower salinity water. This leads to stratification by salinity.