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Q:1 Thunderstorm are severe local storms , which
are of short duration, occurring over small area but are
violent. Discuss the origin and development of
thunderstorm . 12 ½ Marks (200 words)
Ans :Origin of Thunderstorm
Thunderstorms originate when, an air mass becomes so
unstable that it overturns (convicts) violently. Pockets of
rising near-surface air in an unstable air mass expand and
cool, and as some of the water vapour present condenses
into a cloud it releases heat, which then makes the air
parcel even warmer, forcing it to rise still higher in the
atmosphere.
If the lower level air is sufficiently warm and humid, and
the higher altitude air is sufficiently cool, this process
continues until a tall convective cloud the thunderstorm is
formed.
For eg : Thunderstorms are most common in the
afternoon over land, when daytime heating of the land by
the sun causes the lower part of the troposphere to become
unstable from higher temperatures and more water vapour
in the air.
Development of Thunderstorm
Most thunderstorms developed by a cycle that has three
stages:
(1)
Cumulus Stage : The sun heats the Earth’s surface during the
day. The heat on the surface and warms the air around it. Since
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(2)
(3)
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warm air is lighter than cool air, it starts to rise. If the air is moist,
then the warm air condenses into a “ cumulus cloud “. The cloud
will continue to grow as long as warm air below it continues to
rise.
Mature Stage : When the cumulus cloud becomes very large,
the water in it becomes large and heavy. Raindrops start to fall
through the cloud when the rising air can no longer hold them up.
Meanwhile, cool dry air starts to enter the cloud. Because cool air
is heavier than warm air, it starts to descend in the cloud. The
downdraft pulls the heavy water downward, making rain.
This cloud has become a “ cumulonimbus cloud “ because it has an
updraft, a downdraft, and rain. Thunder and lightning start to
occur, as well as heavy rain.
Dissipating Stage : After about 30 minutes, the thunderstorm
begins to dissipate. This occurs when the downdrafts in the cloud
begins to dominate over the updraft. Since warm moist air can no
longer rise, cloud droplets can no longer form. The storm dies out
with light rain as the cloud disappears from bottom to top.
Figure - showing above mentioned developmental stages. Another
type of Thunderstorm called “ Super cell thunderstorm “ which are
much larger, more powerful, and last for several hours.
Q:2 Discuss the Coriolis Force and its significance to Earth
climatic phenomena . 12 ½ M (200 words)
Ans. Coriolis Force is a phenomenon unique to rotating
bodies(Earths bodies) also undergoing translatory motion(
Earth‟s revolution). Its of huge climatic significance to Earth
as it shapes many climatic phenomenon.
It affects the flow of direction of planetary wind system
e.g. rightward deflection in Northern Hemisphere,
Southward deflection in Southern hemisphere.
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It leads to flow of jet stream from west to east direction
as it deflects the wind rightwards and leads to formation of
geostrophic winds.
Coriolis force is one of factors for creation of polar vortex
conditions in Northern & Southern Hemisphere and is also
responsible for circular motion of cyclonic winds e.g.
tropical cyclones of bay of bengal, Easterly anti-cyclones
over
India
during
summers etc.This happens because it deflects vertical
winds towards right/left direction.
Coriolis force is also responsible for alternating motion
of Ocean Currents. Thus, we can see Coriolis Force is a vital
factor that impacts multiple climatic phenomenons and in
turn effects human life & other life forms on Earth in more
ways than one .for ex: agricultural practices, Indian
Monsoons etc.
Q.3: What are cyclones? Distinguish between
tropical and temperate cyclones.
(12 ½ Marks, 200 words)
Ans: Cyclones are winds circulating around an area of
low pressure. They circulate anti-clockwise in northern
hemisphere and clockwise in southern hemisphere. They
are categorised by wind speed by Saffir-Simpson scale
They are characterized by the following features—
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1.
Size of tropical cyclones varies considerably. Their
diameter ranges between 80 km and 300 km. But
sometimes they become so small that their diameter
restricted to 50 km or even less.
2.
These cyclones affect only the coastal area of the
continent. Because these cyclones originate in the
ocean and their intensity decreases as they move
towards the interior area of continent.
3.
The center of the cyclone is having an extremely low
pressure and the isobars are circular but fewer in
numbers. This is why winds attain a gale velocity.
4.
They normally moves from east to west under the
influence of trade winds.
Difference between tropical and temperate cyclone:
• Temperate cyclones are formed in mid latitudes (40-60
degrees north/south), while tropical cyclones are
formed in the tropical zone (5-40 degrees north/
south)
• Temperate cyclones happen due to convergence of cold
and hot air masses and tropical cyclones happen due
to convergence of warm dry and warm moist air
masses
• The isobars of temperate cyclones are wedge shaped or
oval shaped, but in tropical cyclones, isobars are
circular.
Q4 : Discuss the various factor and its impact which
involved in ocean acidification. (12 ½ Marks,200 words)
Ans The concentration of carbon dioxide gas in the
atmosphere is increasing day by day mainly due to activities
like burning of fossil fuels, deforestation and production of
cement. The carbon dioxide thus released in the
atmosphere is absorbed by the oceans which play a very
significant role in moderating climate change. When
atmospheric carbon dioxide dissolves into the ocean it
reacts with water through various steps which ultimately
leads to the formation of bicarbonate ions. This causes an
increase in the acidity of sea water( lowering pH)
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Ocean acidification would lead to a reduction in the
availability of carbon ions which are essential for carbonate
mineral formation(shells, coral reefs). It will also make
marine species to experience harmful effects on their health
, growth and reproduction processes and to have
substantial changes in the habitats and food webs.
Reduction in the metabolic rates of jumbo squid, depressed
immune response of blue mussels and problems in locating
sounds for communication are some of the examples for
biological impacts of ocean acidification.
Ocean acidification acts as a platform for the
destruction of marine food chain, ecosystem and eventually
it will accelerate the process of the loss of biodiversity and
climatic change. All these negative factors may intern affect
the global economy to a great extent.
Recent studies show that the current rate of change of
ocean acidification is very fast. The steps taken by
NOAA(National
Oceanic
and
Atmospheric
Administration)show the graveness of the problem and
plead for global attention to mitigate the same. Serious and
conscious attempts to prevent further ocean acidification is
the proper and prompt measure to reduce carbon dioxide
emission and to rescue the globe.
Q5: Japan experiences much more volcanoes than
other countries of the world. Discuss
(12 ½ Marks,200 words)
Ans: Volcano‟s are places where molten lava comes out
vigorously through conduits created by folding/faulting.
Japan along with various island arcs and festoons is located
in western margin of pacific ocean where Pacific plate
collide with Eurasian Plate is susceptible to volcanism
.Pacific plate being composed of denser material forced
downward to 100 Km where it melts in the form of lava and
its volume increases and it has tendency of buoyancy. The
molten lava occasionally comes out through weak zones
thus making Japan more susceptible to volcanos.
Japan‟s origin is a very contested subject among
intelligentsia where some suggest it to be of originated due
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to folding caused by collision of plates whereas others
considered it to be volcanic origin due to ejection of molten
lava formed due to subduction of Pacific Plate.
Occurrence of volcanoes mostly in western margin of
Japan suggests it folded origin and since this folding has
not squeezed great amount of land mass thus volcanoes
find it easier to come out because of least resistance due to
lack of high mountains whereas on Eastern Pacific side this
tendency is reduced because of lofty Rocky and Andes
Mountains.
Thus Japan experiences volcanoes much more because
of its peculiar origin and it narrow horizontal and vertical
expansion.
Q6 : In northern hemisphere ,when we go toward 90
degree latitude the length of the day increases in summer
seasons .critically examine why the length of day increases
and also explain the role of latitude for day and night
increase.
(12 ½ Marks,200 words)
Variation in the length of day and night at different
times of the year is because of the revolution of the Earth.
Revolution is Earth‟s motion in its elliptical orbit around
the Sun at a speed of 18.5 miles per second, one revolution
is completed in 365 1/4 days. The axis of the earth is
inclined to the plane of the ecliptic at an angle of 66 1/2'
giving rise to different seasons and varying lengths of day
and night.
In summer, the Northern hemisphere is tilted towards
the sun. the Rays of the sun fall directly on the Tropic
of Cancer. as a result, these areas receive more heat. the
areas near the poles receive less heat as the Rays of the sun
are slanting. the North Pole is inclined towards the sun and
the places beyond the arctic circle experience continuous
daylight for about six months so popularly referred to as
„Land of the Mid-night Sun‟.
since a large Portion of the northern hemisphere is
getting light from the sun ,it is summer in the regions north
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of the equator. the longest day and the shortest night at
these places occur on 21st June, is called the summer
solstice.
Effects of latitude : Latitude of a place on the earth is
the angular distance of the place from the equator.1' of
latitude is approximately equal to 111 km. Locations on
similar latitudes have similar day lengths where as different
latitudes have different day lengths.
At latitude 0° (the Equator) day length will be
approximately 12 hours. Areas on the Equator have a
constant 12 hours of day light all year round.
Moving away from the Equator As latitude increases to
polar circles - north or south-day length can be seen to
increase to 24 hours in summer or decrease to zero winter.
Q: 7 The circulation of oceanic water originate due
to the combined effect of several factors .Discuss the
factors like Temperature, salinity and density are the
prime causes of oceanic water circulation .
(12 ½ Marks,200 words)
Ans: An Ocean water circulation has a major impact on the
climatic and socio-economic conditions of a country. These
circulations are episodic and zonal and are caused due to
following factors:-
Temperature ,Density and Salinity all are related to each
other and causes water to circulate ,they are the initiator of
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movement of water , This along with other factors like wind
direction, Coriolis force ,orientation of land and ocean
boundary and gravity causes water to flow in horizontal
direction and causes ocean currents.
(1) Temperature is the prime force for movement of
water .Warm water is lighter and floats over the cool
water and causes vertical flow or mixing. when water
is warmed it expand and creates a void in which cold
and nutrient rich water from bottom of the ocean fills
up. Ocean water near the equator receives more
insolation and expands up to a level around 8 cm
above the mean sea level creating a gradient by which
water flows from the equatorial region to pole wards as
major surface currents. On the other hand cold water
from the Polar Regions sing below the warm surface
water and up wells to fill up the vacancy near the
equator
(2) Salinity Difference: Salinity increases the density of
water. Hence oceanic water will flow from the more
saline water to the less saline water when the
temperature of the regions is same. For example, the
current flow from the Atlantic ocean to Mediterranean
sea via Gibraltar strait is caused due to salinity
difference.
(3) Density Difference: As we know that the water move
from the low density to higher density. In addition to
the temperature and salinity, fresh water influx due to
melting of glaciers also changes the density. This
addition of fresh water decreases the density of water.
East Greenland cold current is supposed to be caused
by this reason.
(4) Density and salinity is interrelated. : Water with
higher salinity have higher density and the vice-versa .
water with higher density in heavier and sinks to the
bottom .this not only causes the vertical mixing ,with
temperature difference between the latitudes causing
change in density in the surface level ,water from
denser region flows to the less dense regions causing
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horizontal flow. Apart from these factors precipitation,
pressure, and rotation of earth also plays prominent
role in driving these currents
Hence the oceanic water circulation depends on the
factors such as temperature, Salinity and density. One
should consider these factors together and not
separately.
Q:8 Explain the distribution of fold mountains across
the world on the context of plate tectonics theory.
(12 ½ Marks,200 words)
Ans : Fold mountains are the mountains ranges formed
due to Collison between the plates I.e convergent plate
boundaries. They have been formed and eroded back since
the time earths crust was formed. In the present time these
fold mountain ranges are present in almost all the
continents and mainly 7 major plates are there presentlynorth American, south American, Eurasian, Antarctic,
Pacific, indo austral and African.
(1) North America:
• Rockies- They are tertiary fold mountain range in
west coast of north America and were formed due to
ocean continental collision between Pacific and
American plate.
• Appalachian-they are the fold mountain of north
America on east coast formed in Caledonian hercynian
era when European continent collided with American
continent and then they separated.
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(2)
South America:
• Andes- fold mountain ranges covering countries Chile,
Peru, Ecuador and was formed by o-c between nazca
plate and south American plate.
(3) Europe:
• Alps- also tertiary fold mountains formed by the
collision of African and Eurasian plate.
(4) Asia:
• Himalaya-tertiary Fold Mountains in northern India
formed due to Collision of Indian plate with Eurasian
plate.
• Aravali- eroded mountains that were fold mountain
ranges in ancient times formed due to Collision of
various Micro plates of Indian subcontinent like
singhbhum and aravali plate.
(5) Australia:
• great dividing range- also an eroded fold mountain
range on eastern Australia which was formed due to
Collision of Australian plate with Pacific plate
(6) Africa:
• atlas- fold mountains in north Africa formed by
collision of African and Eurasian plate.
Q:9 Discuss
the factors causing rejuvenation in
landscape and describe the resultant landform.
(12 ½ Marks, 200 W)
Ans: Rejuvenation refers to the increased erosive force of
fluvial agents of erosion due to fall in the base level. it is
thus brought about by a negative change in the base level
and occurs due to following reasons :
dynamic : upliftment of landmass, enhancement of
slope, fall in the level of the mouth of the river etc
ecstatic : fall in sea level due to glaciations, diastrophic
changes leading to emergence of coastline, subsidence of
ocean bottom etc
static : increased volume and flow in river due to river
capture, decreased sediment load
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Rejuvenation pushes back the cycle of erosion to a
younger phase and various landforms can be seen depicting
a topographic discordance or unconformity of younger
forms seen amidst the old often giving rise to
multi/polycyclic features
1.
Valley in the valley topography : Sudden decrease in
sea level or increase the speed of stream causes
vertical erosion producing a narrow deep valley under
existing a wick shallow valley consisting the pair of
terraces about it indicating the end of old valley
2.
Uplifted peneplain: When Sea level decreases, a new
delta is formed at a lesser height
3.
Incised meanders : Stream flowing with high velocity
due to steep slope and high kinetic energy. Most of the
weight of the stream concentrated in the channel
bottom (middle) vertically eroded & producing incised
meanders
4.
Paired terraces: terraces are usually in valley
topography. large number of terraces together called
paired terraces
5.
Knick Point: Smooth longitudinal profile of a river is
disturbed by tectonic hydrological changes, a
discontinuity in the profile called Knick point is
formed.
Q:10 Discuss the concept of cycle of erosion and
bring out clearly the difference between the views of
Davis and Penck. (12 ½ Marks,200 words)
The concept of cycle of erosion deals with the
transformation of an uplifted landmass by the process of
land sculpture into a featureless plain and strives for
explaining what effect can an exogenic force have on the
landscape.
Different geomorphologists put forward various theories
regarding the cycle of erosion.
The basic premises of the theory is based on the fact
that an uplifted landmass after getting eroded goes through
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a cycle of stages as propounded by Morris Davis the whole
cycle is divided into three stages viz the youth,the mature
and the old stage.
Youth stage
This is the first stage that starts right after the period of
upliftment has culminated
The features of this stage are as follows
(a) the absolute height of the landforms remains constant
(b) relative height of landforms increases due to the valley
deepening process done by streaming rivers
(c) formation of deep v shaped and i shaped valleys along
with features like rapids, cascades, benches are done
in this stage
(d) valley Deeping is the main phenomenon observed with
very little amount of lateral erosion
Mature stage
(a)
(b)
(c)
(d)
(e)
the phenomenon of lateral erosion comes into effect
vertical erosion ceases to operate
both the relative and absolute height of relief decrease
the water divide summit start to erode
the earlier formed v shaped valleys now start to widen
up due to increased volume of river and enhanced rate
of abrasion
Old stage
(a) valley deepening process
because of no gradient
completely
disappears
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(b) water divide summit erode further by back wasting
and down wasting
(c) valley becomes flat
(d) features like meanders and ox bow lakes are
prominent which are formed due to deposition of
eroded material
(e) resistant rock strata like monad nocks are visible
(f) the entire valley becomes a feature less plain called
peneplane by william davis
(g) old stage is longest of all the stages
Difference between the views of Davis and Penck
1.
Davis proposed that the process of erosion starts after
the endogenic upliftment had concluded whereas;
penck believed both upliftment and erosion go side by
side
2.
according to Davis upliftment period was small but
rapid while pencks period of upliftment could be of
any length and had differential rates
3.
Davis believed that the landform is a function of
structure,processa and stage while according to penck
landform was largely based on the relationship of rate
of upliftment and rate of degradation
4.
Davis concept of cycle of erosion was largely time
based while pencks concept was time independent
5.
Davis concept was focused on humid areas while
penck based his theory on the regoins having arid
climate
Q:11 Discuss the processes of mechanical and
chemical weathering and show their relationship with
soil formation. (12 ½ Marks,200 words)
Ans:
Mechanical Weathering Processes:
(1)
Block disintegration due to temperature: Diurnal
changes causes rocks to expand and contract and
joints are formed and these rocks than disintegrated
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(2)
(3)
(4)
(5)
(6)
For Notes
along these joints and broken big block are dislodged
from the main rock mass and fall under the impact of
gravity, unloading of super incumbent load also helps
in this.
Granular disintegration due to temperature: This is
more active in hot desert here rocks which are of
coarse grained and are of different colours they absorb
insolation differently and expand and contract
differently causing stress inside the rock and they are
disintegrated in smaller parts.
Block disintegration due to frost: diurnal freeze and
thaw cycle causes alternate expansion and contraction
which introduce tension and stresses due to which
rocks are disintegrated into smaller particles.
Exfoilation or onion weathering due to temperature
and wind:The outer shells of rocks become loose due
to alternate expansion and contraction due to High
temperature during day time and comparatively low
temperature during night respectively and these
loosened shells are removed by strong winds.
Disintegration and exfoilation due to unloading: The
rocks which are buried under thick covers of of
overlaying rocks are disintegrated when they are
exposed to the surface when super incumbent load is
removed and consequent release of confining pressure.
shattering sue to rain shower ans heat: The outer
shells of the rocks are shattered due to sudden light
showers in hot climatic regions mainly in hot desert
areas.
Chemical Weathering processes:
(1)
Solution: This refers to the process of dissolution of
soluble particles and minerals from the rocks with the
help of water in motion but a thin film of water around
a solid particle also leads to chemical dissolution e.g
Limestone-calcium carbonate, dolomites -magnesium
carbonate etc
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(2)
Oxidation: This refers to the process of oxidation of
minerals in presence of water to form mineral oxides
like Iron Oxide, these oxides weakens the rock and
cause disintegration.
(3) Carbonation: carbonation is the reaction of carbonates
and bi carbonates with the minerals The rainwater
having dissolved the atmospheric CO2 percolates
through different horizons of the soils to reach
underlying lime stones which in turn cause more
organic CO2 to be dissolved and which causes more
carbonate rocks and transforming CaCo3 to
Ca(HCO3)2.
(4) Hydration :The process of hydration is refers to the
addition of water to the minerals, this causes volume
change and an exothermic reaction which renders
minerals to be easily available by the process of
carbonation and oxidation.
(5) Hydrolysis: Hydrolysis is the process wherein both the
mineral of the rocks and water molecules decompose
and react in such a way that new minerals are formed.
(6) Chelation: This is the form of chemical weathering by
plants, plants extact minerals from the soils with the
result mineral lattices are disrupted and crystal
lattices are fragmented and thus mineral weathering
takes place.
Physical and chemical weathering are very important
processes by which Soil is formed, Big rock are
converted into big boulders, cobbles and pebbles, sand
an clay. Soil profile is also very much determined by
the process involved in weathering
Q : 12 Discuss the concept of Volcanism and show
how the theory of Plate Tectonics explains the
mechanism of volcanism and volcanic eruptions.
(12 ½ Marks,200 words)
Ans: Volcanism is the process and mechanism through
which magma is generated, moved and solidified forming
various extrusive and intrusive structures. It is responsible
for the formation of oceanic and continental crust,
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movement of the plates, creation of rock cycle and the
formation of various landforms.
Landforms crated by volcanism
a. Volcanic mountains ex. Mount Kilimanjaro, mount
fuziama etc
b. archipelagoes ex. Indonesian, Japan
c. Various underwater features MOR‟s, seamounts,
guyots
d. intrusive structures such as batholith, laccolith, sills
and dykes.
Plate Tectonics Theory and Volcanism:Plate tectonics
theory explains volcanism by the mantle convectional cell
theory propounded by Arthur homes. It states that due to
the interior heat of the earth that is largely primordial heat
and also derived by radioactive decay of minerals, at
different depth inside the the earth mantle convectional
cells set up. some of these cells penetrate the
asthenosphere which is weak and in semi molten state and
reach earth surface.
The viscosity of magma depends on the depth where
they generate.
They are mafic and fluid if come from lower and middle
mantle and form largely extrusive structures. Whereas they
are felsic and extremely viscous if comes from upper mantle
and subduction zones and form largely intrusive structures.
These volcanoes are highly explosive.
Volcanism along convergent boundaries- here
volcanism is due to the subduction of ocean floor. Since
basaltic ocean floor is subducted it forms andesitic lava, it
results into the formation of island arcs. Ex. Along pacific
ring of fire. Volcanic Eruption is highly explosive along
convergent boundaries.
Volcanism along divergent boundaries- Here very fluid
magma comes from middle and upper mantle and lead to
the formation of mid oceanic ridges, sea mounts and
guyots. These eruptions are not explosive.
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Intraplate volcanism- these volcanoes are also called
as hotspots. here magma comes from lower mantle and
outer core boundary. These are ultra mafic and extremely
fluid magma. These magma form Hawaiian type island and
flood lava province like deccan trap.
Thus the convergent, divergent, transformational plate
boundaries are active site for volcanic activity which is
conclusively explained by the PTtheory.
Q13: What do you understand by ‘continental drift’
theory and the ‘plate tectonics’ theory?.
(12 ½ Marks,200 words)
Ans:The plate tectonic theory utilising the concept of sea
floor
spreading
and
convergent
plate
boundary
phenomenon very well explained the origin and growth of
the young fold mountain. Convergent plate boundary can
occur between ocean-continental plate and continentcontinent plate. In such interaction the denser plate usually
subsides and huge compressional force is generated.
In case the plates involved are continental and oceanic
plate. On convergence, the heavier plate, usually the
oceanic plate subsides under the lighter continental plate.
This zone of subduction is called benioff zone. This
subduction of heavy plate under the lighter plate cause
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tremendous compressional force. This compressional force
compresses the sedimentary material and pushes them
upwards. Thus Fold Mountains are formed. The denser
plate which subsides reach deep in mantle melts due to
extreme heat and expands in volume. This tends to push
the fold mountain even higher thus the upward movement
is helped by the melting of the denser plate. Ex : the andes
and rockies are formed by convergence of the pacific plate
with the south American and north American plates
respectively.
Continental Drift theory had been
proposed by Alfred Wegner in 1912, it talked about
distribution of continents and the oceans. According to
Wegner all continents used to form a single land mass
known as PANGAEA and there was a mega ocean called as
PANTHALASSA. However, around 200 million years ago
Pangaea began to split into two large land masses called as
Lauraisa and Gondwanaland which subsequently broke
into many smaller continents.The theory is backed by the
following evidences:
(1) Jig Saw fit: The Africa and South America continents
are almost a perfect fit at 1000 fathom line.
(2) Rocks Age: As per the radiometric dating Rocks on the
two sides of above mentioned continents are of the
same age.
(3) Tillite: It‟s a sedimentary rock formed out of deposits of
glaciers. The sediments in India have counter parts
found in six different landmasses of Southern
Hemisphere.
(4) Placer Deposits: Ghana have rich placer deposits of
gold in spite of having no source rock there but in
Brazil.
(5) Distribution of Fossils: Plants, animals and fossils
have been found to be identical across continents like
Africa, Madagascar, India etc.
Continental drift theory was a prominent theory for
quite some time, however, ocean floor mapping and similar
studies post war period changed the view and people moved
towards convectional theory and plate tectonic theory etc.
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Q:14 Discuss the life-cycle of a temperate cyclone
and also describe the weather associated with it.
(12 ½ Marks,200 words)
Ans: Life cycle of the temperate cyclone was proposed by
Bjerkens and H Soleberg. it explains the complete cycle
from formation to dissipation.
Life Cycle
The life cycle of temperate cyclone consist of six stages
which are:
(a) Initial stage of undulating zone called polar front.
(b) Beginning of cyclonic circulation.
(c) Warm sector well developed.
(d) Cold Front overtakes warm front.
(e) Occlusion.
(f) Dissipation.
Between the prevailing westerly‟s and polar easterlies lie
a more or less permanent undulating baroclinic zone known
as polar front, along which most extra tropical cyclones
originate. As the cold air mass pushes under the warm air
mass a knick point develops around which cyclonic
circulation starts which is anticlockwise. The tongue of
advancing equatorial air mass called warm sector has a
leading warm front and the lagging cold front at the
interface of two air masses. If these air masses neither
advances nor retreats, they form a stationary airmass which
is for short duration. Eventually the cold front pushes warm
sector aloft and the warm sector is occluded by cold front.
Associated Weather
(a)
Warm front: Along the warm front which extends
south to south east there is a veering wind shift from
anticlockwise to clockwise direction as the front
passes, with maximum speed ahead of front. There is
a drop of barometric pressure which levels off when
the warm front pass. the front is associated with
stratified clouds mainly Nimbostratus with light ad
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widespread rainfall. the visibility becomes poor and
there is fog in precipitation area. An appreciable rise in
temperature with scattered cumulonimbus clouds is
observed when the front passes completely.
(b) Cold Front: There is a veering wind shift from
anticlockwise to clockwise direction as the cold front
passes with rise in barometric pressure. Steep slope of
cold front favours the formation of cumulonimbus
clouds
with
associated
heavy
rainfall
and
thunderstorms. Once the cold front passes the
temperature drops appreciably and there is clear sky
with scattered cumulous clouds.
Q:15 Discuss the development of local winds, and
their influence on local weather, giving three examples
of the well-known local winds in the world.
(12 ½ Marks,200 words)
Ans: Local winds occur on a small spatial scale, their
horizontal dimensions typically several tens to a few
hundreds of kilometres. They also tend to be short-lived
lasting typically several hours to a day. There are many
such winds around the world, some of them cold, some
warm, some wet, some dry. There are many hazards
associated with the winds.
The main types of local winds are Sea breezes and land
breezes, Anabatic and katabatic winds, and Foehn winds.
Katabatic Winds: Katabatic (downslope) winds occur
over slopes which are cooled. Katabatic winds occur where
air in contact with sloping ground is colder than air at the
same level away from the hillside over the valley (see
diagram below). Katabatic winds are nocturnal phenomena
in most parts of the world (i.e. they tend to happen at night)
as there is surface cooling, especially when there is little
Katabatic wind speeds do not typically not exceed 3 or 4
m/s. However, where the ground is covered with snow or
ice, katabatic winds can occur at any time of day or night
with speeds often reaching 10 m/s, or even more if
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funnelling through narrow valleys occurs. Katabatic winds
may lead to the formation of frost, mist and fog in valleys.
Sea Breezes: Sea breezes are the result of differential
heating of the land and the sea. Sea breezes occur by day,
when the land becomes warmer than the sea. Warm air
from the land cannot expand into the sea as the air is cooler
and more dense, so it expands up into the atmosphere.
Cumulus clouds tend to form as the warm air rises over the
land to about 500-1500m.
The Bise: A cold dry wind which blows from the northeast, north or north-west in the mountainous regions of
southeastern France and western Switzerland in winter
months. The bise is accompanied by heavy cloud.
The Chinook Wind:A warm, westerly wind found in
western North America – Canada and the USA, when air
from the Pacific blows over the Rocky Mountains and other
upland areas. On January 15th, 1972, the Chinook caused
the temperature in Lorna, Montana to rise from -48°C to
9°C in 24 hours! The fastest wind speed recorded during a
Chinook was 107mph, in Alberta, Canada.
The Crachin: The name given to the drizzly weather
with low stratus, mist or fog which occurs from time to time
during the period January to April over the China Sea and
in coastal areas between Shanghai and Cape Cambodia. It
occurs when cool, moist air from the north encounters
warm, moist air, and it is intensified by orographic lifting
and/or by coastal convergence.
The Etesians/meltemi: The strong northerly winds
which blow at times over the Aegean Sea and eastern parts
of the Mediterranean Sea during the period May to October.
The winds are known as meltemi in Turkey.
The Föhn (or foehn): The Föhn is a warm, dry, gusty
wind which occurs over the lower slopes on the lee side (the
side which is not directly exposed to wind and weather) of a
mountain barrier. It is a result of forcing stable air over a
mountain barrier. The onset of a Föhn is generally sudden.
For example, the temperature may rise more than 10°C in
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five minutes and the wind strength increase from almost
calm to gale force just as quickly. Föhn winds occur quite
often in the Alps (where the name föhn originated) and in
the Rockies (where the name chinook is used). They also
occur in the Moray Firth and over eastern parts of New
Zealand‟s South Island. In addition, they occur over eastern
Sri Lanka during the south-west monsoon.
Anabatic winds: This wind is caused by thermal (heat)
processes. Anabatic (upslope) winds occur over slopes
which are heated by the sun. Air which is in contact with
slopes that are warmed expands upward and cool and sinks
over neighbouring valleys . Anabatic winds are usually slow,
at only 1-2m/s and are rarely importance expect near
coasts where they can increase the strength of sea breezes.
Land breezes :Land breezes occur at night and in the
early morning, when the land is cooler than the sea. This is
because as the air cools in the night time (as there is less
heating from the sun) it contracts. Pressure is higher over
the land than the sea. This causes the air to flow from the
land to the sea which is known as a land breeze. The
circulation is completed by air rising and moving towards
the land at 100-300m.
Q:16 Define air masses. How do they originate?
Classify them and state the characteristics of any one
type.
(12 ½ Marks,200 words)
Ans: Air masses are large bodies of air which have
temperature and moisture characteristics nearly the same
in the horizontal.
The regions where air masses form are referred to as air
mass source regions. If air remains over a source region
long enough, it will acquire the properties of the surface
below. Ideal source regions are regions that are generally
flat and of uniform composition.
Air masses are classified according to their temperature
and moisture characteristics. They are grouped into four
categories based on their source region. Air masses that
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originate in the cold, polar regions are designated with a
capital “P” for polar. Air masses that originate in the warm,
tropical regions are designated with a capital “T” for
tropical. Air masses that originate over land will be dry and
are designated with a lowercase “c” for continental. Air
masses that originate over water will be moist and are
designated with a lowercase “m” for maritime. These letters
are combined to indicate the type of air mass:
• cP: cold, dry air mass
• mP: cold, moist air mass
• cT: warm, dry air mass
• mT: warm, moist air mass
Continental Polar (cP): Continental Polar air masses are
also cold to cool and dry, but are not as cold as the Arctic
air masses. Continental Polar air masses form over Canada
and Siberia. These air masses bring cold air during the
winter and cool, relatively clear, rather pleasant weather in
the summer. The air mass is stable and usually prevents
cloud formation. As the Continental Polar air move south
across the warmer land, the lower portion of the air mass
may become sufficiently modified by warming to cause a few
clouds to form within the air mass.
Q :17 Discuss the nature and composition of earth’s
atmosphere. (12 ½ Marks,200 words)
Ans: Atmosphere is the mixture of different gases & it
envelops the earth all around. It contains the life giving
gases like Oxygen for humans animals & carbon dioxide for
plants.
Nature Of Atmosphere :The atmosphere is a deep
blanket of gases and suspended liquids and solids that
entirely envelops the earth. Compared to the radius of the
earth however, the atmosphere is a very thin layer of air.
Half the atmosphere lies below a height of 18,000 ft. It is
important to note down here , Air is an integral part of the
earth‟s mass & 99% of the total mass of the atmosphere is
confined to the height of 32 km from the earth‟s surface.
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Influenced by solar radiation, seasonal temperature and
precipitation changes, rotation of the earth, and air/water
properties. The atmosphere is structured in layers,
including the troposphere, which supports life, and the
stratosphere, which contains the protective ozone layer.
Composition Of Atmosphere : The atmosphere is
composed of gases, water vapour & dust particles.
Gases :
(1)
Nitrogen - 78% - Dilutes oxygen and prevents rapid
burning at the earth‟s surface. Living things need it to
make proteins. Nitrogen cannot be used directly from
the air. The Nitrogen Cycle is nature‟s way of
supplying the needed nitrogen for living things.
(2) Oxygen - 21% - Used by all living things. Essential for
respiration. It is necessary for combustion or burning.
(3) Carbon Dioxide - 0.03% - Plants use it to make
oxygen. Acts as a blanket and prevents the escape of
heat into outer space.It is transparent to the incoming
solar radiaton but opaque to outgoing terrestrial
radiation.
(4) 40 Trace gases - gases found only in very small
amounts. They include neon, helium, krypton, and
xenon etc.
Water Vapour : It is decreases with altitude in warm &
wet tropics, it may account four percent of the air by
volume, while in dry & cold areas of the desert & polar
region, it may be less than one percent of the air. It also
absorb parts of the insolation from the sun & preserve the
earth radiated heat. water vapour also contributes to the
stability & instability in the air.
Dust Particles :These are generally concentrated in
lower layers of the atmosphere. The higher concentration of
dust particles is found in sub -tropical & temperate regions,
due to dry wind in comparison to equatorial & Polar
Regions. Dust & salt particles act as hygroscopic nuclei
around which water vapour condenses to produce cloud
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Q:18 List the important water bodies and ice caps in
news due to changes in the geographical features. Trace
the reasons for change. (12 ½ Marks,200 words)
Ans Some of the important water and ice bodies in news
due to changes are(1) Himalayan glaciers; Have been receding continuously
for last few decades and areas earlier covered in ice are
now ice free for most of the year.
(2) Polar ice caps; Have been shrinking each year,
threatening wildlife on one side and opening potentials
for resource exploration on the other.
(3) Ice free oceans in north Canada; opening a potential
sea route around the poles.
(4) Aral sea; Due to river diversion had dried up, turning
surrounding areas to desert. Has seen limited revival.
(5) Dead sea; Has been shrinking due to diversion of River
Jordan for irrigation. It already has no life due to high
salinity.
(6) Tropical oceans are seeing mass bleaching of corals,
while corals have expanded beyond their erstwhile
habitat due to warming oceans in temperate regions.
(7) Rivers worldwide are being polluted, threatening
marine life and usability by humans. Ex. Yamuna and
Ganga in India and Yangtse in China(missing Baji
dolphins).
The reasons for these have been abuse of resources by
humans.
(1) Global warming due to greenhouse gases.
(2) Industrial, agricultural, city waste being released into
water bodies without treatment.
(3) Diversion of water, construction of dams and
encroachment on basin areas.
Q: 19 How did Perigean moon impact tides around the
world and especially in India?discuss the different type of
tides and causes of occurrence. (12 ½ Marks,200 words)
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Ans:
Tides is the periodic rise and fall of the oceanic water. It
is one of the three primary movements of the ocean water
and happens as a result of geometric mean of the
gravitational pull of the sun and the moon exerted on the
earth.
There are two types of tides:
(a)
(b)
Spring tide.
Neap tide.
Apart from them one more is sometimes considered as tide
which is:
(c)
Sieches
Spring Tide: The gravitational pull of the sun and
moon act simultaneously, which cause strong high
tides. Spring tides generally occur when there is full
moon or new moon day. On further classification,
when moon is closest to the earth, vis-à-vis Perigean
moon, the collective pull increases causing higher rise
in sea levels, which is called King tide or Perigean
Spring tide.
Neap Tide: When sun‟s pull and moon‟s pull are
exactly at the right angle then it is called neap tides.
These are low tides as the effective gravitational force
is least compared to all other positions of the sun and
moon.
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Sieches:These are witnessed as a result of periodic
rise and fall of water in enclosed bodies like lakes and
bays due to their inherent period of oscillations.
Perigean moon Impact On Tide: Perigean moon is a
celestial position of moon when it lies closest to the
earth. The resultant gravitational pull on oceanic
water is maximum producing a bulge that much
higher than spring tide. As a result coast around the
world witness far greater inundation of water
exceeding the high tide level thus demanding the
evacuation of marginal coastal areas.
In India the Perigean moon tidal bulge is witnessed
along the eastern coast of T.N. this combines with the
low pressure exhorted oceanic swell and the extra river
flow due to monsoon season to produce much higher
tide that will inundate vast tracts of the coastal areas
Q:20 The greatest concentration of volcanoes is located in
the Circum – Pacific region, known as ‘Pacific Ring of Fire’.
Examine why and also explain features of these volcanoes.
(12 ½ Marks,200 words)
Ans :The Pacific “Ring of Fire” is a string of volcanoes
and sites located on most of the Earth‟s subduction zones
having highseismic activity, or earthquakes, around
the edges of the Pacific Ocean. Roughly 90% of all
earthquakes occur along the Ring of Fire.
Reason for greatest concentration of volcanoes in
circum pacific region is the tectonic movement of
plates. Tectonic plates are huge slabs of earth crust which
fits into each other like pieces of puzzle. They are not fixed
and moving atop liquid mantle. Due to this movement at
some places they are going apart from each other and some
places they are moving toward each other. Former is called
divergent boundary and latter is called convergent
boundary. At convergent boundary, subduction of tectonic
plates results into slipping of heavier plates under lighter
plates creating deep trenches.
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As the heavier plates goes inside the mantle, it gets
converted into hot magma with gases due to high
temperatures. As magma is lighter than mantle, it tends to
get outside with pressure through cracks and when this
magma comes out it is called lava and such active spots are
termed as volcanoes.
Similarly at divergent boundary also, magma comes
outside through the rifts created by plate movement away
from each other. As this activity went on for millions of
years , a number of volcanoes were created alongside the
boundaries of these tectonic plate known as “Ring of Fire”.
Features of these volcano:
1.
2.
Many of these volcanoes are very violent and Active,
made by basaltic lava which spread over large area.
They have created western pacific arcs of volcanic
island. Although these arcs are made by volcanic
activity but they are not violent. It is argued that here
the heavier rock which is subducting, is comparatively
softer due to which sudden violent eruptions don‟t
occur.
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