exam cram t2 Flashcards

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1
Q

what is the meaning of weathering

A

the mechanical fracturing and chemical decomposition of rocks by natural agents on the surface of the earth

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2
Q

what are the 3 types of weathering

A

physical or mechanical weathering
chemical weathering
biological weathering

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3
Q

list 2 types of physical weathering

A

insolation and exfoliation

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4
Q

explain block disintegretation

A

arid environments receive direct sunlight in the daytime and rapid radiation at night which leads to exposed rocks expand during the day and contract during the night. Eventually joints or cracks develop and large masses of rock break down into smaller blocks

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5
Q

what is exfoliation

A

it is the formation of curved rock shells which separate in succession from the original rock masses, leaving behind successively smaller spherical bodies

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6
Q

what is exfoliation also called

A

spaling

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7
Q

why is exfoliation called onion peeling

A

because the shells which split away look like the layers of an onion being peeled away

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8
Q

describe exfoliation in deserts

A

in deserts some of the rock surfaces are so heated that a thin shell-like layer pulls away and splits away from the cooler interior.

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9
Q

how are rectangular blocks of rocks rounded

A

by exfoliation

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10
Q

where are exfoliation domes formed

A

over the top of a single large body of massive rock

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11
Q

how thick r individual rock shells

A

6-15 metres

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12
Q

give 2 examples of exfoliation domes

A

north dome and basket dome at yosemite

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13
Q

what is scree

A

the angular fragments of rock which get collected at the base of exfoliation domes

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14
Q

where can we see granular disintegration

A

crystalline rocks with coarse mineral grains

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15
Q

explain granular disintegration

A

heterogenous rocks are composed of various minerals with different rates of expansion and contraction, this leads to stresses within the rock and disintegration starts. This creates gravel or sand in which each grain consists of a single particle, the rocks fall apart grain by grain

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16
Q

where is chemical weathering most prevalent

A

in hot and humid areas

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17
Q

what is the most active substances for a chemical reaction

A

oxygen, carbon dioxide, rainwater, organic acids

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18
Q

list 4 types of chemical weathering

A

oxidation, carbonation, hydration, solution

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19
Q

explain oxidation

A

oxygen dissolved from air by rainwater reacts with iron sulphide present in rocks and converts it into ferric hydroxide. It is a yellow or brown crust which forms on the surface of many rocks and it readily crumbles

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20
Q

explain carbonation

A

rainwater dissolves co2 from the atmosphere and forms carbonic acid, when the acidic rain falls on calcareous rocks like limestone and chalk, the calcium carbonate or magnesium carbonate reacts with the acid to form calcium bicarbonate which is washed away by rainwated

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21
Q

explain hydration

A

this involves the action of water on some minerals, some minerals have the ability to absorb water and increase in size, they are subsequently weakened and changed into another compound

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22
Q

give an example of hydration

A

anhydrite is hydrated to gypsum

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23
Q

explain solution

A

rainwater is able to dissolve certain materials and leach through the rocks, the rocks become weak and decompose

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24
Q

list 5 differences between physical and chemical weathering

A
  • in physical the rocks are disintegrated while in chemical they decompose
  • in the physical, only the size and shape change, there is no change in physical composition. In chemical, chemical reactions occur leading to the formation of new substances and changes in the chemical composition
  • physical weathering is more effective in the dry and hot areas or cold and wet areas. Chemical weathering is very effective in the hot and humid regions
  • in physical weathering the rocks r affected to a great depth, in chemical only the surface of the rocks are affected
  • in physical, the strong minerals are effected while in chemical minerals like quartz r difficult to weather
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25
Q

what is biological weathering also known as

A

organic weathering

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26
Q

how do animals help in weathering

A

burrowing animals create tunnels within weathered rock zone and soil which allowed greater percolation of rainwater and helps disintegrate the rocks.
Earthworms help to churn the soil and bring to the surface fine materials in the form of casts.

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27
Q

how do plants assist in physical weathering

A
  • the expanding power of roots helps with mechanical disintegration of rocks, this exerts a lot of pressure which widens and deepens cracks and crevices. Rainwater and air enters the cracks which furthers the weathering
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28
Q

how do plants assist in chemical weathering

A

the decay of plant matter and formation of humus results in the creation of organic acids like humic acids which help in the decomposition of rocks

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29
Q

how do humans aid in weathering

A

they engage in deforestation which leads to the soil losing the binding factor of roots and soil erosion exposes fresh rock surfaces to weathering.

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30
Q

list 4 constructive effects of weathering

A
  • weathering causes the formation of soil in which plants grow and crops are raised
  • chemical weathering helps in the formation of new minerals which have economic benefits
  • weathering exposes mineral layers which can be mined easily
  • weathering exposes rocks like limestone and dolomite used in construction and manufacturing of cement
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31
Q

list 2 destructive effects of weathering

A
  • the loss of life and property is caused due to the sudden movement of regolith as in the case of landslide and slumping.
  • mud flows in mountainous areas cause widespread destruction
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32
Q

what is the hydrosphere

A

liquid and frozen water on the surface and groundwater in the soil and the rocks is called the hydrosphere

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33
Q

what are tides

A

the periodic rise and fall in the level of the open oceans and seas, twice in 24 hours

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34
Q

what causes tides

A

the gravitational pull of the sun and moon

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35
Q

what is the synodic month

A

the time taken by the moon to complete one orbit (29.53 DAYS)

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36
Q

what influences the height of tides

A

the relationships among the sun, moon an

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37
Q

when is the moon said to be in conjunction with the sun

A

when the sun and moon are on the same side of the earth so that all the three bodies are in a straight line

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38
Q

when is the moon said to be in opposition with the sun

A

when the moon and sun are on opposite sides of the earth

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39
Q

what does the term syzgy mean

A

it is used when all three celestial bodies are in a straight line.

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40
Q

how many times do the moon and sun combine to produce the high tides

A

twice a month

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41
Q

what is quadrature

A

this is when the celestial bodies are positioned so that the rays drawn from the moon and the sun to the earth make a 90 degrees

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42
Q

what is a lunar day

A

the time that elapses between the moon passing twice over any one meridian on the earth

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43
Q

how long is a lunar day

A

24 hours, 50 mins

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44
Q

what is high water

A

the rise of water level to a maximum

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45
Q

what is low water

A

when the ocean level falls to a minimum between two high waters

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46
Q

how many high and low waters r there in a lunar day

A

2 each

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47
Q

what is tidal range

A

the difference in height of the water at low tide and high tide

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48
Q

where is the tidal range maximum

A

spring tides

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49
Q

when do spring tides occur

A

twice a month during new moon and full moon when a syzgy occurs

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50
Q

what are spring tides

A

the tides produced when the tide producing forces of the moon and sun work together.

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51
Q

when do highest spring tides occur, what are they called

A

equinoxes, equinoctial springs

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52
Q

when do neap tides occur

A

when the moon and the sun are at quadrature in the phases of first and third quarter

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53
Q

what are neap tides

A

unusually small tides caused when the sun and moons tide producing forces balance each other out

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54
Q

what are perigean tides

A

tides which occur when spring tides coincide with the moons perigee leading to abnormally great tidal range

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55
Q

what are apogean tides

A

when neap tides coincide with apogean tides, the tidal range is abnormally small

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56
Q

what are the 5 layers of the atmosphere

A

troposphere, stratosphere, mesosphere, ionosphere, exosphere

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57
Q

what is the average height of the troposhere from the surface of the earth

A

15 km

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58
Q

what is the height of the troposphere at the poles and at the equator respectively

A

8 km, 18km

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59
Q

in which layer is the air densest

A

troposphere

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60
Q

what is the normal lapse rate of the troposphere

A

1 degrees celsius per 165 m of ascent

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61
Q

in which layer do weather elements occur and why

A

troposphere because it contains water vapour and dust particles

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62
Q

why is the troposphere a zone of turbulence

A

the horizontal wind system on the earths surface in conjunction with the vertical air currents transfer heat. Hence is generates a turbulent zone where intense mixing of hot and cold air occurs

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63
Q

what is the height of the stratosphere

A

it extends to a height of 50km

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64
Q

why is the stratopshere used for flying aircrafts

A

this is because it does not contain water vapor and dust particles. Hence, there is an absence of turbulence and weather phenomena.

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65
Q

what are polar stratospheric clouds

A

iridescent sheet-like clouds in the polar regions which are harmful sites of stratospheric ozone destruction

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66
Q

why is stratosphere a zone of inversion

A

this is due to the presence of ozone in the stratopshere which absorbs the solar radiations of some wavelengths including uv radiation

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67
Q

at what height is the ozonosphere

A

at approximately 13-35 km within the stratosphere.

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68
Q

how much ozone is found in the ozonosphere

A

ninety percent of the atmospheres ozone

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69
Q

how is ozone formed

A

due to the splitting of oxygen molecules by high energy solar photons. The single oxygen atoms then combine with o2 to form ozone.

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70
Q

where does the ionosphere lie

A

75-1000km from earth

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71
Q

what is the temperature in the ionosphere

A

500 degrees in the lower parts to 1500 degrees in the upper parts

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72
Q

how is the ionosphere ionised

A

it is ionised by high energy plasma, ultraviolet rays and x-rays from the sun as well as cosmic rays which enter the atmosphere.

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73
Q

why is the ionosphere unique

A

the charged particles refract and reflect radio waves which are vital for long distance radio communications

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74
Q

where is the magnetosphere

A

upper region of the ionosphere

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75
Q

which layer causes the aurora borealis and aurora australis

A

magnetosphere

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76
Q

what is the ionosphere also known as

A

thermosphere

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77
Q

what is the magnetosphere

A

the layer where the behavior of charged particles is strongly affected by the magnetic field of the earth and the sun

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78
Q

what is the exosphere

A

the region where molecules from the atmosphere can overcome the pull of gravity and escape into outer space

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79
Q

what is the uppermost layer of the atmosphere

A

the exosphere

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80
Q

what is the lower boundary of the exosphere

A

the exobase

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81
Q

where r satellites parked

A

exosphere

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82
Q

at what height does the exosphere merge with interplanetary space

A

10,000 km

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83
Q

what is the exosphere composed of and what does that thing do

A

ionised hydrogen which reflects uv rays from the sun and creates a geocorona

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84
Q

what is the function of ozone in the stratosphere

A

it forms a safety shield by absorbing UVB radiation, it maintains the stability of the climatic conditions over the surface of the earth.

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85
Q

what is the effect of tropospheric ozone

A

it is harmful to living organisms and damages our health , the forests and also reduces crop yields

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86
Q

how ozone formed in the troposphere

A

formed by sunlight acting on pollutants

87
Q

list 3 factors of depletion of ozone

A
  • The use of CFCs which are in things like ACs, Spray Cans, Fridges. When CFC reach the stratospheres they are broken down into chlorine atoms by UV, a single atom of chlorine can destroy 100,000 molecules of ozone
  • the hydrocarbons released by automobile exhausts and jet aircrafts can cause the depletion of the ozone layer
  • the stratospheric clouds in the polar regions are composed of the crystalline compounds of water, nitric acid, sulphuric acid at very cold temperature of -85 degrees which destroys the ozones in the stratosphere
88
Q

what is global warming

A

the rise in the temperature of the atmosphere

89
Q

explain the greenhouse effect

A

carbon dioxide is increased by burning fossil fuels and cutting forests. The carbon dioxide traps the heat being reflected from the earth although some heat is lost. The warming increases water vapor in the air leading to even greater absorption of heat which lead to rising temperatures melting snow and ice increasing ocean levels

90
Q

list 6 effects of climate change

A
  • it will lead to rising sea levels and inundation of low lying levels
  • it will cause severe floods and droughts in different parts of the world
  • the spread of tropical diseases will increase
  • there will be an increase in the tropical cyclones, cloud bursts and storms
  • warmers temperatures will make it hard for animals like polar bear and penguins to survive, coral reefs are also getting destroyed
  • crops grow in specific temparature and rainfall condition, the rise in temperature will affect the production of crops, all crops will not properly develop in high temperature.
91
Q

what is insolation

A

the solar radiation which strikes the earth

92
Q

what is terrestrial radiation

A

during the day, earths surface receives radiant short wave energy via insolation. At night, the heat absorbed during the day is lost to space in the form of long wave radiation

93
Q

list 6 factors affecting the temperature of a place

A
latitude
altitude
distance from sea
slope of land
wind
ocean currents
94
Q

how does latitude affect the temperature of a place

A

in the torrid zone, the direct rays concentrate the heat over a small area and the insolation is very high. In higher latitudes, the angle of incidence of the suns rays decline and the intensity of the insolation is less as heat is spread over a larger area

95
Q

how many months of darkness and continuous lights r there in the polar regions

A

6 each

96
Q

when is the lapse rate greater, day or night

A

day

97
Q

how does altitude affect temperature

A

As the atmosphere is heated directly, the places nearer the surface are much warmer than on mountain slopes. The lower layers of the atmosphere hold more water vapour hence the absorption of heat is greater than the upper layers who hold less water vapour

98
Q

how does distance from sea affect temperature

A

oceans and coastal plains tend to have low annual range as they are infleucned by land and sea breeze and experience maritime, insular or oceanic climate.

99
Q

why does delhi have a higher range than thiruvananthapuram

A

this is because of delhis continentality

100
Q

how do ocean currents affect climate

A

the cold currents are influential along the western coasts of the continents in the tropical and sub-tropical regions. The cold currents flowing from the polar regions keep the summer temperature from rising and keep the coast ice-bound for at least 9 months. The warm currents make the summers warm, keep the winters mild and the winds blowing over them become moisture-bearing winds

101
Q

list 2 effects of the gulf stream

A
  • the southern and eastern coast of the united states are warmed by gulf stream
  • labrador current meets the gulf stream and produce thick fog, the nutrient rich water of the Labrador current mixes with the warm water of the gulf stream to create conductive condition for plankton generatiion
102
Q

list 4 effects of north atlantic drift

A
  • it helps getting warm equatorial water to the coast of europe
  • the relatively warm waters of the north atlantic drift are responsible for moderating the climate of western europe
  • being a warm current, the north atlantic drift helps keep many norwegian ports free of ice throughout the year
  • the westerlies bring adequate rainfall to the british islands throughout the year as the winds are warmed by the north atlantic drift
103
Q

list 4 effects of labrador current

A
  • it produces heavy fog and sustained rich fishing ground
  • in spring and early summer icebergs are carried southward which create hazardous conditions for ships
  • the labrador current has marked a moderating effect on the climate of coastal labrador and newfoundland
  • cool temperature and fogs are especially common in summer
104
Q

what happens when gulf stream and labrador current meet

A

it helps in the distribution of nutrients throughout the water and made the areas some of the richest fishing ground in the world

105
Q

list 4 effects of kuro shio and oya shio

A
  • kuroshio keeps the coastal region of japan warm
  • oyashio current cools the adjacent coastal area
  • oyashio current abounds in plankton and is beneficial to cold water fish
  • in north japan where kuroshio meets oyashio current they form a rich fishing ground
106
Q

how do slopes affect climate

A

steeper the slopes, the faster will be the fall in temp,

107
Q

how do winds affect climate, 4 points

A

winds transport heat to maintain balance

  • permanent wind like westerlies carries tropical air to temperate areas
  • in winter, the interior of asia becomes extremely cold and freezing as winds blow in outward direction
  • local winds like loo raise temperature during summer in rajasthan
108
Q

what is atmospheric pressure

A

the pressure exerted upon the earth by the blanket of air surrounding the earth which has weight and occupies space

109
Q

how does altitude affect the distribution of air pressure

A

altitude increases, pressure decreases,
The layers just above the earths surface are compressed and the densest. With the increase of height, the atmosphere tends to become rarified and the pressure continuously falls

110
Q

what are the 3 factors of distribution of air pressure

A

altitude, temperature, rotation of earth

111
Q

at what rate does atmospheric pressure decline with height

A

declines at the rate of 1cm fall in height of mercury column for every 110 m ascent

112
Q

how are temperature and atmospheric pressure related

A

inversely related

113
Q

how does temperature affect atmospheric pressure

A
  • Heated air expands and tends to rise which reduces atmospheric pressure
  • cold air contracts, it becomes heavy and subsides increasing atmospheric pressure
114
Q

list 3 points on how rotation of the earth affects atmospheric pressure

A
  • due to rotation, the air rising above equator is pushed towards the poles and moves in the upper troposphere
  • the speed of rotation at the pole is slow and the air is thrown outwards from the poles towards the equator
  • less air is left in the subpolar region and the temperate cyclone in the region helps to reduce atmospheric pressure
115
Q

list the 4 major pressure belts

A
  • equatorial low pressure belt
  • sub-tropical high pressure belts
  • sub- polar low pressure belts
  • polar high pressure belts
116
Q

where is the equatorial low pressure belt located

A
  • between 5 degree north to 5 degrees south
117
Q

what is the intertropical convergence zone

A

equatorial low pressure belt

118
Q

why is the equatorial low pressure belt called doldrums

A
  • due to excessive heating, horizontal movement is absent here and only convectional currents r there, it is called doldrums due to the virtual absence of surface winds
119
Q

why is there rapid evaporation and high humidity in the equatorial low pressure belt

A

high temperature

120
Q

what is 4’o clock rain

A

afternoon thundershowers accompanied by lightning and torrential downpour in the equatorial low pressure belt

121
Q

where is the sub tropical high pressure belts located

A

30-35 degrees north and south

122
Q

why are the sub tropical high pressure belts known as horse latitudes

A

in olden days vessels with cargo of horses passing through these belts found difficulty sailing under the calm conditions. They used to throw horses in the sea in order to make the vessels lighter

123
Q

y r the sub tropical high pressure belts a zone of divergence

A

the descending air currents form the trades and the westerlies on the surface

124
Q

why do sailors avoid doldrums

A

this is because in the past their movements were stalled here

125
Q

why are the equatorial low pressure belts called the inter tropical convergence zone

A

because the northeast trades and the southeast trades meet here

126
Q

what type of weather is found in the sub tropical high pressure belt

A

anti-cyclonic weather, winds r dry and weather is stable

127
Q

where is the subpolar low pressure belt located

A

between 60-70 degrees north and south of the equator

128
Q

why is the subpolar low pressure belt a zone of convergence

A

the cold polar easterlies and westerlies blow over the warm current to generate cyclonic weather

129
Q

where is sub polar low pressure belt best developed

A

over oceans

130
Q

where is the polar high-pressure belt located

A

around the pole up to 70 degress north and douth

131
Q

what is the temperature of the polar high pressure belt

A

extremely low temperature throughout the year causes the air above the frozen surface to become cool, dense and heavy which then subsides and forms high pressure belt

132
Q

how are global wind belts created

A

air blowing at the base of the circulation cells, from high pressure to low pressure

133
Q

name 2 factors affecting direction and velocity of wind

A

pressure gradient, coriolis effect

134
Q

what does pressure gradient mean

A

wind blows from high pressure to low pressure, greater the gradient, faster the speed

135
Q

what does coriolis force mean

A

wind blows towards its right in northern hemisphere and left in southern hemisphere

136
Q

where does the amount of deflection of wind increase

A

towards the poles

137
Q

what are the 4 types of wind systems

A

planetary winds, periodic winds, variable winds, local winds

138
Q

name 3 planetary winds

A

trade winds, westerlies, easterlies

139
Q

name 2 period winds

A
  • land and sea breeze

- monsoon winds

140
Q

name 2 variable winds

A

cyclones, anticyclones

141
Q

name a local wind

A

loo

142
Q

why is the trade wind called so

A

it is because it facilitated commerce between people on opposite shores

143
Q

where do trade winds blow from and to

A

from sub-tropical high pressure areas towards the equatorial low-pressure belt.

144
Q

where do trade winds lie

A

between 5- 30 degrees north and south

145
Q

where do westerlies blow from and to

A

from sub-tropical high-pressure belts towards sub-polar low pressure belts

146
Q

what are polar easterlies

A

dry, cold prevailing winds that blow from the polar high-pressure belts to the temperate low pressure belts

147
Q

why do trade winds bring heavy rainfall on eastern sides of tropical islands

A

this is because they are warm hence they pick up moisture

148
Q

at what speed do trade winds blow

A

regularly at a constant speed

149
Q

what are trade winds associated with

A

constant depressions and cyclones

150
Q

what are trade winds also known as

A

permanent or constant winds

151
Q

what degrees do westerlies blow

A

35-60 degrees north and south of the equator

152
Q

why are westerlies known as anti-trade wind

A

because they blow opposite to the trade winds

153
Q

where do westerlies bring rain to and when

A

they bring rain to mediterranean region when the pressure belt shift in winter

154
Q

which wind helped to draw in temperate cydlone

A

westerlies

155
Q

what are the roaring 40s, furious 50s, screaming 60s

A

in the southern hemisphere between 40-60 degrees, westerlies blow with a great force over vast oceans, they are known was the roaring 40s, furious 50s, screaming 60s

156
Q

why are westerlies unable to blow forcefully in the northern hemisphere

A

due to the presence of large land masses

157
Q

in summer which winds does the mediterranean region come under the influence of

A

trade winds

158
Q

why do hot dry deserts form on the western margin of continents

A

trade winds become dry and offshore on the western margins of continents after continuously shedding moisture from east to west coast

159
Q

what happens when large masses of cold polar air meet the warm westerlies

A

forming fronts and temperate cyclons r generated

160
Q

what do polar winds cover in winter in the northern hemisphere

A

large parts of north america and asia

161
Q

what is the cause of formation of periodic winds

A

differential heating of land and sea

162
Q

when do periodic winds change direction

A

they change periodically with the change in season or diurnally

163
Q

what produces monsoon phenomena

A

difference in temperature over the continents and water bodies

164
Q

explain sea breeze

A

during the day the sun heats up both the ocean surface and the land. Water heats up more slowly than land so the air above the land will be warmer compared to the air above the ocean, the warm air over the land will rise causing low pressure at the surface. The wind will blow from the higher pressure over the water to lower pressure over the land causing sea breeze

165
Q

explain land breeze

A

at night, the roles are reversed. The air over the ocean is now warmer than the air over land, the land loses heat quickly after the sun goes down, the ocean however can hold onto the heat which causes the low surface pressure to shift over to the ocean during the night and the high surface pressure to move over to the land so the wind will blow from land to ocean .

166
Q

explain summer monsoon

A

in summer low pressure develops over northwestern india and an uninterrupted pressure gradient develops from subtropical high in southern hemisphere to northwestern india, the southeast trade wind cross the equator under the influence of coriolis and gets deflected and enters as southwest monsson over peninsula india and myanmar

167
Q

why does southwest monsoon give ample rainfall

A

it is an onshore wind

168
Q

explain winter monsoon

A

in winter formation of intense high pressure in northern plain blows out the wind as surrounding water bodies experience comparatively low pressure, so the wind system reverses. the northeast monsoon winds are generated and they blow from high pressure belt of northern plan to water bodies in the south. they are dry as they are offshore winds

169
Q

how can northeast monsoon winds bring rain to coromandel coast if theyre dry

A

this is because if they blow over a stretch of moisture they can absorb moisture

170
Q

what is chinook

A

a warm wind known as snow eater

171
Q

what is foehn

A

a warm dry southerly wind off the northern side of the alps

172
Q

what is mistral

A

a cold northerly wind from central france and the alps to mediterranean

173
Q

what is loo

A

a hot wind which blows over plains of india

174
Q

what are variable winds

A

winds which blow in a small area and are related to the pressure systems

175
Q

why are variable winds called variable winds

A

this is because they do not blow in a definite direction and their speed and velocity varies with the pressure system

176
Q

what is a cyclone

A

a rotating storm with low pressure at the centre and high pressure at the periphery

177
Q

what is the center of the cyclone

A

a small region of light variable wind

178
Q

how do the winds in a cyclone move in the northern hemisphere

A

in an anti clock wise direction

179
Q

how do winds in a cyclone move in southern hemisphere

A

clockwise direction

180
Q

why dont cyclones form at the equator

A

due to the weak coriolis force

181
Q

where do tropical cyclones originate

A

between 6 to 20 degrees north and south of equator

182
Q

how is the pressure gradient in a tropical cyclone

A

extremely steep

183
Q

what is the wind speed of a tropical cyclone

A

may be over 225 kmph

184
Q

why is tropical cyclone destructive

A

it causes immense loss of life, loss of property, storm surge, high waves along sea beaches etc.

185
Q

what is the cause of tropical cyclone

A

heating of water bodies in the torrid zone during summer

186
Q

what is the cause of temperate cyclone

A

meeting of cold air from the polar region and moist warm air from the tropical region

187
Q

how is the pressure gradient in the temperate cyclon

A

low

188
Q

what is wind speed of temperate cyclone in winter

A

40-60 kmph

189
Q

how destructive is temperate cyclone

A

less destructive

190
Q

what is an anti cyclone

A

a system of winds that rotates around a center of high atmospheric pressure

191
Q

what are cyclones commonly known as

A

lows

192
Q

what are highs

A

anti-cyclones

193
Q

what are cyclones indicators of

A

bad weather

194
Q

what are anti-cyclones indicators of

A

fair weather

195
Q

how do cyclones work

A

air close to the ground is forced inward toward the center of the cyclone where pressure is the lowest. it then begins to rise upward, expanding and cooling in the process. This cooling increases the humidity of the rising air which results in cloudiness.

196
Q

how do anti cyclones work

A

air at the center of an anticyclone is forced away from the high pressure that occurs there. That air is replaced in the center by a downward draft of air from higher altitudes, as this air moves downward, it is compressed and warmed. This warming reduces the humidity of the descending air

197
Q

what is humidity

A

the amount of water vapour present in the air

198
Q

what is saturation point

A

the amount of water vapour the air can hold

199
Q

define rain

A

water vapour condenses around the dust particles to form droplets of water. These droplets of water float in the atmosphere to form clouds. The water droplets eventually become heavy and fall on the surface of the earth as rainfall

200
Q

what is drizzle

A

when the size of the water droplets is less than 5mm in diameter

201
Q

define snow

A

when the air temperature in the upper layers of the atmosphere goes below the freezing point, condensation takes place in the form of snowflakes, it reaches the earths surface as snow

202
Q

what clouds do hail form in

A

thunderstorm clouds

203
Q

define hail

A

The upward rising convectional currents lift frozen pellets high up in the atmosphere. These pellets grow large and heavy. They fall on the earths surface as hailstones which may be as heavy as 1 kg

204
Q

what are the 3 types of rainfall

A

convectional rainfall, oreographic rainfall, cyclonic rainfall

205
Q

explain convectional rainfall

A

the ground gets heated and the air becomes lighter and rises.
The condensation of moisture in the upper strata takes place, the air cools down and descends to replace the rising warm air

206
Q

what accompanies convectional rainfall

A

thunder and lightning

207
Q

give a real example of convectional rainfall

A

this rainfall takes place daily in the equatorial region and is known as 4’o clock rain

208
Q

why is the leeward side called the rain shadow area

A

because little rainfall is caused here

209
Q

explain oreographic rainfall

A

moisture-laden wind blows from the sea to the land transversely to the mountain barrier, it meets with an obstruction in the form of a mountain range. the air rises, condensation takes place, clouds are formed and it rains on the windward side. The leeward side receives dry air and there is no rainfall

210
Q

why is california a desert

A

the westerlies are obstructed by the coastal ranges

211
Q

give an example of oreographic rainfall in india

A

mumbai is on the windward slope so it receives heavy rainfall while pune receives less rainfall as it is on the leeward slope.

212
Q

explain cyclonic rainfall

A

the rainfall takes place in an area of low pressure with ascending air, the warm and cold air masses meet. The warm air being lighter rises above the cold air, a warm front is formed.

213
Q

in which regions does cyclonic rainfall occur

A

tropical and temperate regions

214
Q

which form of rainfall receives different forms of atmospheric turbulence

A

cyclonic rainfall