Author: Manuj Notebook: Environment and Geography

Created: 8 July 2014 at 8:19:12 PM

Updated: 22 May 2021 at 1:28:42 PM

GS I: Geography World Physical

MANUJ JINDAL AIR 53 — GEOGRAPHY NOTES WORLD GEO

Origin of Earth

Early hypothesis by German philosopher Immanuel Kant known as the Nebular

Hypothesis
Laplace revised it in 1796
The hypothesis proposed that planets were formed out of a cloud of material
associated with a youthful sun, which was slowly rotating.
In 1950, Otto Schmidt in Russia and Carl Weizascar in Germany somewhat
revised the "nebular hypothesis” by adding that sun was surrounded by solar
nebula containing mostly the hydrogen and helium along with what may be
termed as dust. The friction and collision of particles led to the formation of a
disk-shaped cloud and the planets were formed through the process of
accretion.
1900: Chamberlain and Moulton considered that a wandering star approached the
sun. As a result, a cigar-shaped extension of material was separated from the solar
surface. As the passing star moved away, the material separated from the solar
surface continued to revolve around the sun and it slowly condensed into planets.
Modern Theories:
Big Bang Theory or the Expanding Universe Hypothesis
Edwin Hubble in 1920 provided evidence for the fact that the universe

is expanding
Main points of Big Bang Theory:
In the beginning, all the matter was concentrated in a singular
 atom or a tiny ball with an unimaginably small volume, infinite
temperature, and infinite density.
At time of the Big Bang, the ball exploded and led to expansion
of the ball. (temperature of the universe very high at this time)
Over time, the temperature goes down and atomic matter is
generated.
An alternative to this was Hoyle’s concept of steady state. It
considered the universe to be roughly the same at any point of time.
However, with greater evidence becoming available about the
expanding universe, scientific community at present favours argument
of expanding universe
Formation of Stars
Dense cloud bodies eventually collide to form stars.
A galaxy contains a large number of stars. Galaxies spread over vast
distances that are measured in thousands of light-years. The
diameters of individual galaxies range from 80,000-150,000 light years.
A galaxy starts to form by accumulation of hydrogen gas in the form of
a very large cloud called nebula. Eventually, growing nebula develops
localised clumps of gas. These clumps continue to grow into even
denser gaseous bodies, giving rise to formation of stars. The formation
of stars is believed to have taken place some 5-6 billion years ago
Our solar system
Our solar system consists of the sun (the star), 8 planets, 63 moons,
millions of smaller bodies like asteroids and comets and huge quantity
of dust-grains
Out of the eight planets, mercury, venus, earth and mars are called as
the inner planets as they lie between the sun and the belt of asteroids
the other four planets are called the outer planets.
Alternatively, the first four are called Terrestrial, meaning earth-like as
they are made up of rock and metals, and have relatively high
densities. The rest four are called Jovian or Gas Giant planets.
The difference between terrestrial and jovian planets can be
attributed to the following conditions:
The terrestrial planets were formed in the close vicinity of the
parent star where it was too warm for gases to condense to
solid particles. Jovian planets were formed at quite a distant
location.
The solar wind was most intense nearer the sun; so, it blew off
lots of gas and dust from the terrestrial planets. The solar winds
were not all that intense to cause similar removal of gases from
the Jovian planets.
The terrestrial planets are smaller and their lower gravity could
not hold the escaping gases
Big Splat
Giant collision or impact of a body three times the size of
Mars collided into the earth and blasted large part of the earth into the
space resulting in the moon.
Formation of Atmosphere (Solar Winds, Degassing, Condensation,
Photosynthesis)
Three stages:
The first stage is marked by the loss of primordial atmosphere.
 The early atmosphere, with hydrogen and helium, is
supposed to have been stripped off as a result of the
solar winds. This happened not only in case of the earth,
but also in all the terrestrial planets, which were supposed
to have lost their primordial atmosphere through the
impact of solar winds
In the second stage, the hot interior of the earth contributed to
the evolution of the atmosphere.
During the cooling of the earth, gases and water vapour
were released from the interior solid earth.
This started the evolution of the present atmosphere. The
early atmosphere largely contained water vapour,
nitrogen, carbon dioxide, methane, ammonia and very
little of free oxygen.
The process through which the gases were outpoured
from the interior is called degassing. Continuous volcanic
eruptions contributed water vapour and gases to the
atmosphere. As the earth cooled, the water vapour
released started getting condensed.
The carbon dioxide in the atmosphere got dissolved in
rainwater and the temperature further decreased causing
more condensation and more rains. The rainwater falling
onto the surface got collected in the depressions to give
rise to oceans. The earth’s oceans were formed within
500 million years from the formation of the earth.
Finally, the composition of the atmosphere was modified by the
living world through the process of photosynthesis
Differentiation
The geological process by which the Earth came to have its present interior
structure is called differentiation, and is illustrated in the following figure.

The Earth and the Universe

Sun’s surface temp. 6000 degrees celsius and over 20 million degrees in the core
Mercury is closest to the sun and Venus is second — called earth’s twin as similar
mass, size and density
Moon revolves around the Sun every 27 days
Mercury > Venus > Earth > Mars > Jupiter (12 satellites and bands of gases) >
Saturn (three rings and 9 satellites) > Uranus (rotates around the sun in clockwise
direction from east to west, 5 satellites) > Neptune
Rotation and Revolution
The earth rotates on its own axis from West to East once in every 24 hours,
causing day and night
The earth also revolves round the sun in an orbit once every 365(1/4) days
causing seasons
Revolution
In an elliptical orbit at the speed of 18.5 miles per second
Leap year is one extra day added every four years because 1/4 day is
not possible to be shown on the calendar. (actual time taken by earth
to revolve around the sun is 365 1/4 days)
Impacts of Inclination of the earth on its Axis:
Varying Lengths of Day and Night:
The axis of the earth is inclined to the plane of the ecliptic (the
plane in which the earth orbits round the sun) at an angle of 66.5
degrees, giving rise to different seasons and varying lengths
of day and night.
If the axis were perpendicular, all the places on the earth would
have the equal days and nights at all times of the year, but this
is not true.
In the northern hemisphere, in winter as we go northwards, the
hours of darkness steadily increase. At the arctic circle, the sun
never rises and there is darkness throughout the day in mid-
winter on 22nd December. Beyond this, the number of days with
complete darkness increases as we move towards the North
pole where half the year is in darkness.
Summer, this condition is absolutely reversed, with 6 months of
light on the North Pole.
The Altitude of the Midday Sun — equinoxes
The inclination of earth on its axis changes the altitude of the
midday sun.
The sun is vertically overhead at the equator two times a year
(two days), generally falling on 21st March and 21st September
(dates can change) and these are termed as equinoxes
meaning equal nights. (all parts of the world have equal
nights and days on these two days).
June or Summer Solstice: After March equinox, the sun is
vertically over head at the Tropic of Cancer (23.5 degree N). on
about 21 June. This is the summer solstice, when the northern
hemisphere will have its longest day and shortest night.
December or Winter Solstice: By December 22, the sun is
vertically over head at the Tropic of Capricorn (23.5 degree S).
This is the winter solstice, when the southern hemisphere will
have its longest day and shortest night.
Thus, Tropics mark the limit of the Overhead sun
Seasons
As explained above about the tilt of the earth to its axis of about
66.5 degrees, there is a variation in the sunlight received by
different parts of the earth at different times.
Earth's distance from the sun does not cause the season to
 change. This is mainly due to other factors that mask this
change. These factors are land and sea distribution, and
atmospheric circulation.
Instead, Earth's seasons come and go because Earth does not
rotate with its axis exactly upright with respect to the plane of
our world’s orbit around the sun. Earth's axial tilt is 23.5
degrees. This puts the Sun farther south in December and
January, so the north has winter and the south has summer.
Thus winter falls on that part of the globe where sunlight strikes
least directly. Summer falls on that part of the globe where
sunlight strikes most directly.
On equator, the period of refracted light is shorter than the temperate
zone.
Latitudes and Longitudes:
Latitude is the angular distance of a point on the earth’s surface, measured in
degrees from the centre of the earth.
Important latitudes: Tropic of Cancer (23.5 N), Tropic of Capricorn
(23.5 S), Arctic Circle (66.5 N), Antarctic Circle (66.5 S).
Distance of 1 degree of latitude is approx. 69 miles, but remember that
 it is no same across the earth because the earth is slightly flatter at the
poles.
Useful for calculating distance from the Equator of a place. Eg: a place
located at 18.55 degree N. (Bombay) is 18.55 X 69 miles = 1280 miles
from the equator.
Longitude is the angular distance, measured in degrees, along the equator
east or west of the Prime Meridian.
Greenwich is the prime meridian at 0 degrees from which all other
meridians radiate eastwards and westwards up to 180 degrees.
Longitudes help in determining local time in relation to GMT.
Every 1 degree of longitude change represents 4 minutes of time.
Hence, every time we move 15 degrees, the time moves by 60 minutes
of one hour.
Hence, if we move 15 degrees east wards, we add an hour to
the local time against which we are comparing as the earth
rotates west to east. This is vice-versa if we move east to west.

Earth's Interior:
Most knowledge about the earth's interior is based on mainly indirect sources because it
has not been possible to access inner levels of earth's structure

Evidence about Earth's Interior:

We get evidence of the structure of earth's interior from the following:

1. Rocks on the surface of earth and rocks obtained from mining

2. High Levels of Pressure and Temperature Downwards
Volcanic eruptions throwing out hot and molten lava from earth's interior and
the existence of hot springs, geysers etc. point to an interior of earth which is
very hot.
This high temperature is attributed to:
Internal Forces
Automatic disintegration of radioactive substances
Chemical reactions
Pressure also increases as we go in, so the core is a rigid mass - the
layer enveloping the core is semi-solid.
3. Behaviour of Earthquake Waves
Body Waves: P Waves and Surface Waves: L Waves
P Waves (longitudional nature or parallel to the direction of the wave), S
Waves (transverse nature or perpendicular to the direction of waves)
and L Waves (surface) are three types of earthquake waves
P Waves travel through both liquids and solids (faster in solids than liquids)
while the S waves only travel through solids while L waves travel on the
surface only
P waves slow down as they travel inwards into the core - pointing to a less
solid layer (a characterstic of the longitudnal wave that it travels faster in
more dense areas) and increase in velocity as they travel through the hard
inner core, and then decrease again in velocity for a while.
S Waves do not pass through liquids, and hence are not present in the
molten portion as they get deflected - again pointing to a molten, semi-solid
layer below the crust and the mantle.
Shadow Zone:
Earthquake waves get recorded in the seismograph however there are
certain areas where they don;t get recorded. These are known as
shadow zones and are created due to the properties of the P and the
S Waves.
SHADOW ZONE DIAGRAM below
4. Evidence from the Meteorites
Meteorites are freely traveling bodies in the space that fall into the earth's
atmosphere and collide with the earth's crust.
Their heavy inner core shows similarities to earth's inner structure as well
5. Gravitation - greater near the poles and less near the equator - Gravity anomalies
 occur due to differences in the distribution of material inside the surface and hence
give us understanding of the interior of the earth
6. Magnetic Field of earth and seismic activity

Sectional Profile of Earth's Interior

1. Crust
The outermost solid part of the earth is known as the crust or the lithosphere
Its thickness varies from oceanic to continental areas — oceanic crust is
thinner than the continental crust
Mean thickness is 5 km for oceanic crust and 30 km for the continental crust
Lowest density of rock here — around 3 g/cm3
The oceanic crust is made of basaltic rock and the continental crust of the
granitic crust
The SIAL forms continental crust (silica and aluminum) and the SIMA forms
the oceanic crust (silica and magnesium)
2. Mantle
The boundary between the crust and mantle is known as M-discontinuity or
Moho.
This second layer is known as mantle or mesosphere
About 1800 Km thick
Outer layer behaves like a thick plastic while the inner layer is composed of
ultra basic rock
Density > Crust but < Core; density increases as we move deeper
The asthenosphere (from Greek asthenēs 'weak' + sphere) is the highly
viscous, mechanically weak and ductilely-deforming region of the
upper mantle of the Earth. It lies below the lithosphere, at depths between
~80 and ~200 km (~ 50 and 124 miles) below the surface. The lithosphere-
asthenosphere boundary is usually referred to as LAB.
Its from asthenosphere that molten rock material escapes to earth.
Magma inside earth and called lava once on the surface
3. Core - NIFE Nickle and Ferrous
Highest density minerals here
It's liquid first and then solid again the center as indicated by the S-Waves
Geosyncline:
A geosyncline is a very large depression in the earth's crust, filled with a deep layer of
sediments derived from the land masses on each side and deposited on the floor of the
depression over a long period of time.
MOVEMENTS OF EARTH - Agents of change on earth
Causes of movements:

Heat generated by the earth's radioactive interior

Movement of crustal plates due to tectonic forces
Forces generated by the rotation of earth
Climatic factors
Isostacy - blocks of earth's crust, because of variations in density would rise to
different levels and appear on the surface as mountains, plateaus, planes or ocean
basins

Earth's Movements:

Endogenic
Diastrophism - slow bending, folding, warping and fracturing of the earth's
crust
Epeirogenic - Upward and Downward
Upward or downward lifting of the earth's surface consists of
Epeirogenic movements
Causes in formations of raised beaches, sea caves, fossiliferous
sea beds above sea level. Deccan is believed to have gone
through this
Orogenic - Tension and Compression
 Mountain forming movements act tangentially to the earth's
surface as in plate tectonics
Tensions (away force) produce fissures and Compression
produces folds
Earthquakes
Occurs when surplus accumulated stress in the rocks in the earth's
interior is relieved through weak zones over the earth's surface in
form of kinetic energy of wave motion causing vibrations on the earth's
surface.
Two Major types and other types: Tectonic and Volcanic are major
ones. Others are collpase earthquakes caused due to collapse of
mining roofs, explosion of chemical or nuclear devices may cause
ground shaking called explosion earthquakes, and earthquakes that
occur in the areas of large reservoirs are known as Reservoir Induced
Earthquakes.
Measured in Ritcher Scale and the intensity is recorded on a scale of
1-10 with intensity scale named after Mercalli - an Italian seismologist
(range 1-12)
Focus or hypocenter: The place of origin of the earthquake inside the
earth;s surface is called focus.
Epicenter: Point right above focus where the maximum impact of the
earthquake is felt is called the epicenter
Causes:
Slipping of rock formations along faults and fractures in the
earth's crust
This happens due to constant change in volume and
density of rocks due to intense temperature and
pressure in the earth's interior
Volcanic activity can also cause earthquakes
Tsunamis caused by earthquakes. Other hazards: ground shaking,
ground settlement, soil liquefaction, land and mud slides, ground
lurching, avalanches, groun displacement, floods from dams and leeve
failures, fires
Example of Earthquake and their impact on the geography of the area:
2015 Earthquake in Nepal caused large scale destruction and
death of over 7000 people in the Himalayan nation.
The earthquake was caused due to movement of the
tectonic plates across the Indo-Australian tectonic plate
and the Asian tectonic plate in the Nepalese Himalayas.
The Indo-Australian plate has been moving northwards
into the Asian plate for millions of years, causing the
Himalayas to rise every year. This resulted in
accumulation of stress in the tectonic plate rocks, which
was released, causing the earthquake.
Other Landform Impacts:
Surface faulting is displacement that reaches the earth's
surface during slip along a fault. Commonly occurs with
shallow earthquakes, those with an epicenter less than 20
km.
Ex : Hector Mine surface rupture after 1999 earthquake in
southern California
 Subsidence: the earth’s surface subsides or moves down
in comparison to previous or sea level
Ex : seen at many places in japan after 2011 tohoku
earthquake
Tectonic uplift : uplift of more than 9 feet was seen
during the 1964 Great Alaska Earthquake
Soil Liquefaction : when soils with a high water content
are violently shaken they lose their mechanical strength
and behave like a fluid and so buildings can literally sink.
Ex: 2011 Japan earthquake
Avalanches : avalanche is a rapid flow of snow down a
sloping surface. Occurred in the himalayan region during
the recent Nepal Earthquake
Landslides - earthquakes often cause landslides,
especially in steep river valleys and areas of weak rocks.
Tsunami - an earthquake on the sea floor or close to the
coast may cause huge waves.
Ex : tsunami of 2004
Change in course of rivers: generally occurs due to
tectonic upliftment or subsidense
Ex: change in course of Mississippi river following the
Madrid earthquake

Volcanoes
A volcano is formed when molten magma in the earth's interior
escapes through fissures and vents to the crust of the earth
Features of Volcanoes in diagram below.
Types:
Conical or central type or Composite - cone formation of
the volcano due to cooled lava accumulated from many
eruptions around the vent of the volcano. These are
characterised by cooler eruptions and more vicious lavas
than basaltic lava. eg: Fujiyama and Mt. Vesuvius in Italy
Formed by Acid lava, which is light in color, with
high quantity of silica, flowing slowly and seldom
travel for longer distances. They solidify soon and
hence form steep sided slopes resulting into conic
volcanoes.
Shield Type or lava domes - Largest forms of volcanoes
on the earth made up mostly of basalt or basic lavas
which are the hottest lavas and highly fluid. Shield
volcanoes are formed when this basic lava pours out and
spears across a wide plateau formed around the vent with
slightly sloping area around it. Eg: Hawaii Islands
Basic lavas are dark in color with basalt, iron and
magnesium. They are less viscous, very fluid and
have low amount of silica.
Flood Basalt Provinces or Fissure Type - Magma
escapes small fissures or cracks in the crust and spreads
over a large area before finally spreading over the surface
 forming a fissure type volcano. Highly Fluid Magma. Eg.
Deccan trap
Caldera - During an eruption material from top of the
cone is blown off or collapses into the vent widening the
orifice into a large crater. Some volcanoes may have
these becoming more enlarged and hence be called
calderas, which can be several miles long. These are a
result of violent eruptions accompanied by the
subsidence of much of the volcano into magma beneath.
Water may collect in the crater or the caldera forming
crater or caldera lake.
Eg: Lonar in Maharastra and Krakatao in Indonesia
Mid Oceanic Ridge Volcanoes - Across the mid oceanic
ridge in the Pacific and Atlantic oceans.
Intrusive Volcanic Landforms:
Plutonic Rocks - cooling lava rocks inside earth's
crust
Volcanic rocks - cooling lava rocks on surface of
earth
Batholiths - large rock masses formed due to
cooling of magma inside the earth and forming
large domes of cooled magma - form core of huge
mountains. Note diagram below.
Laccoliths - intrusive counterparts of an exposed
domelike batholith
Dykes - solidified vertical lava layers inside the
earth
Sills - solidifies horizontal lava layers inside the
earth

WHY DO MOST VOLCANOES APPEAR AROUND THE RING OF

FIRE?
The Pacific Ring of Fire is a 2000 mile-long region running along
the North American Western Continental Border, across to the
Oceanic Ridge along the East coast of Japan, down South to
the Indonesian Islands . This ring of fire running across the
ocean and forming sort of a ring or concentric chain of active
volcanic activity.
Most volcanoes appear around the ring of fire because it is the
region where the major Pacific tectonic plate and the tectonic
Asian tectonic plates converge or meet.
These are the converging margins of these plates where two
plates meet head-on to each other. In addition, the convection
currents of the mantle converge here causing rising limbs of
convection current leading to creation of ridges along this plate.
The large volcanic activity in this region takes place as the
radioactive material from the earth's mantle tries to escape
through the fissures, vents and cracks formed due to the
convergence of these plates and convetion currents.
The location of volcanoes on the steep continental borders near
great ocean deeps and in or near youthful mountains correlates
them definitely with zones of weakness in the earth's crust.
Geysers
Confined almost to USA (Yellowstone national park), Iceland and New
Zealand
 Fountains of hot water and super heated steam that may spout up to a
height of 150 feet above the surface of the earth.

Both internal and external forces are constantly changing the earth’s
surface through four processes:

1. Weathering
2. Erosion
3. Transportation
4. Deposition

Weathering:

The gradual disintegration of rocks by atmospheric or weather forces is

known as weathering.
Weathering is physical, chemical and biological.
Physical: Disintegration of rocks by mechanical forces is physical
weathering. Fine particles of rocks is created due to pressure and
action of forces on these materials. No change in chemical
composition.
Eg: repeated temperature changes in deserts lead to physical
weathering as cracks appear in the rocks. When round boulders
are exposed to such regular splitting away of layers of rocks, it
is known as exfoliation.
Another example is due to frost action.
Chemical: Decomposition of rocks due to exposure to air and
water. Minerals inside the rocks undergo chemical changes when they
come in contact with the atmosphere - water and air which contain
chemical components in small quantities to bring these changes.
Temperature can start these chemical reactions.
Three major chemical weathering processes:
1. Solution or Hydration
Many minerals are dissolved by rain water, as it
contains enough carbon dioxide to make it a weak
acid.
This is specially true for limestone regions where
the rain water attacks and dissolves the calcium
carbonate of which the rock is chiefly formed.
2. Oxidation
Reaction of oxygen in air or water with minerals in
the rock.
Eg: most rocks contain some iron which reacts with
oxygen in the air to change to iron oxide.
3. Decomposition by organic acids
Bacteria on rock produce acids, which when
dissolved with water, help to speed up weathering
of underlying rocks.
Biological: Disintegration, break-up abd decomposition of rock
masses by plants, animals and acitivities of man.
 Mass Movement
Soil Creep — gradual but more or less continuous movement of soil
down hill slopes.
Soil Flow (Solifluction) — When soil is completely saturated with water
the individual particles are almost suspended in the water and move
easily over one another and over an underlying rock.
Landslides
Porous and Pervious Rocks (or permeable)
Porous rocks are those which have many pore-spaces between the
grains. Water is easily absorbed by these rocks and stored in the pore-
spaces.
Permeable or pervious rocks are those which allow water to pass
through them easily.
Rocks maybe porous but not pervious because they may absorb
water but may not allow it to pass through pores internally.
Similarly, rocks may be pervious, i.e, allowing water to pass through
internal spaces but not porous, that is not absorbing much water. Eg:
granite.

Erosion - ice, river water, sea, wind, underground water

Rivers or running water — single most important denudation agent in the

world.
Uplands form catchment areas of rivers.
Dendritic Drainage — when streams of running water flow in a tree-like
appearance. This happens when bed rocks on which the streams flow have
uniform resistance to erosion hence the streams join the main valley
obliquely.
Trellised Drainage — when streams of running water flow in a rectangular
pattern. This happens when bed rocks on which the streams flow have both
soft and hard rock structure.
Stages in river's life: Young, Mature, Old
Upper Course or Young Stage — mostly vertical corrasion
Gorges — eg: Indus Gorge in Kashmir
River Capture or river piracy or river beheading
Rapids, cataracts and waterfalls

Potholes
 Gulleys
V Shaped Valleys
Middle Course — Mostly lateral corrasion
Meanders

Interlocking spurs
 Alluvial planes start forming here
Old:
Numerous streams of river forming
Ox Bow Lakes
Terraces in a flood plain
Swamps
Delta
Bird’s foot delta of Mississippi
Arcuate delate of Ganges, Mekong and the Nile (fan
shaped)
Cuspate delta (tooth-shaped) of Ebro in Spain
Estuarine delate (Amazon, Ob) — partly submerged in
coastal area
Alluvial Terraces
River Rejuvenation
Depositional Landforms of Rivers:

Alluvial Fans and Cones

Depsoited material of a river which acquires shape of a fan or cone and
appears as a series of continuous fans is called alluvial fans
Natural Levees
Ridge of sediment deposited naturally alongside a river by overflowing
water.
Delta
Formed at the mouth of the river where it deposits the alluvial material
brought by it at the mouth of the river into the ocean
Deltas are formed in the regions of low tides and coastal plains.
Ganga and Brahmaputra, Krishna, Kaveri and Mahanadi form delta.
Estuaries
The sharp edged mouth of rivers, devoid of any deposits is known as
Estuary.
Regions of high tides and rift valleys witness Estuaries.
Estuary does not have fertile lands.
Narmada and Tapi form Estuaries

Glacial Erosion and Landforms

Glaciers are four types: continental, ice-caps, piedmont glaciers, and valley glaciers

Continental Glaciers are found in Greenland and Antartica. These move in all
directions from their central portions
Ice-caps are the covers of snow and ice on mountains from which the valley or
mountain glaciers emerge
Piedmont glaciers form a continuous ice sheet at the base of the mountains as in
southern Alaska. They are formed by converging of several glaciers into a massive
ice-mass.
Valley Glaciers are found in higher or upper regions of Himalayas and all such high
mountain ranges in the world. These move downwards from the top origination
 points
Ice-caps first melt into ice shelves and then into icebergs which eventually melt into
water.
Two major ice caps left: Greenland and Antarctica
Erosional Features:
Cirque/Corrie - Mature stage
It is an amphitheatre shaped hollow basin cut into a mountain ridge. It
may develop into a tarn lake when the ice melts.
Glacial Trough - Mature Stage
Original Stream cut valley further modified by the glacial actions
U Shaped Valley - Old Stage
Since the glacial mass is slow and heavy the erosion activity is slow
causing in the formation of a U Valley
Hanging Valley - Mature Stage
When smaller tributaries are unable to cut as deep as the bigger ones
and remain hanging at the higher levels than the main valley as
discordant tributaries
Arete - Young stage
Is a steep sided, sharp-tipped summit with the glacial acitivity cutting
into it from two sides
Horn - Young stage
Is a ridge that acquires a horn shape when the piedmont glacier
surround the summit

Depositional features in Glaciers:

Outwash Plain
When the glacier reaches the melting stage of its life, it leaves behind
stratified depositional material consisting of rock, debris etc. This layered
surface is called an outwash plain or a till plane
Esker
Winding ridge of assorted gravel running across the outwash plain
Kame Terraces
Broken Ridges looking like hummocks in a till plain
Drumlin
 Inverted Boat shaped deposition in a till plain caused by deposition.
Kettle Holes
Basins forms in a till plain are called kettle holes
Moraine
General term applied to the rocks, gravel, sand, etc. carried by the glacier.
These could be terminal moraines or gorund moraine depending on their
location they have different names

Karst Region

A region with a large stretch of limestone. Has a very distinct topography.

Deserts — Hot Deserts and Mid-Latitude Deserts

Hot Deserts: Sahara, Thar, Atacama, Great Australian desert, Mohave desert,
Massawa, Arabian Desert, Namib and Kalahari Deserts
Their aridity is caused by off-shore trade winds, hence also known as trade
wind deserts.
Major hot deserts located on the western coasts of the continents between
latitudes 15 degree N. and 30 degree N. and S.
Reason why these deserts are so dry:
Lie across the Horse Latitudes or the Sub-Tropical High Pressure Belts
where the air is descending, a condition least favorable for
precipitation of any kind to take place.
The rain bearing winds blow off-shore and the Westerlies that are on
shore blow outside the desert limits.
Whatever winds reach the desert blow from the cooler to warmer
regions, and their relative humidity is lowered, making condensation
impossible.
High temperature range due to quick heating and cooling of the earth.
Mid-Latitude Deserts: Gobi Desert, Turkestan (Kashgar)
Extreme temperature ranges, even more so than hot deserts
Surrounded by high hills and mountains and hence precipitation is low as
clouds are blocked off
Severe winters with extremely low temperatures
Vegetation (both)
Xerophytic or drought resistant scrub
Plants have deep and long roots to search for water
They have thin, waxy, leathery, hairy or needle shaped foliage to reduce loss
 of water through transpiration
They have very few or no leaves
Some have thick succulent stems to store water
Seeds are surrounded by thick and hard shell and lie dormant and only
become active on rain

PLATE TECTONICS:
Movement of large sections of earth's crust takes place due to three reasons:

1. Polar Wandering
Relative movement of the earth's crust and upper mantle with respect to the
rotational poles of the earth
2. Continental Drift
Movement of the continents relative to each other.
Proposed by Alfred Wegener in 1922
Originally there existed a huge continental mass called the Pangaea which
was covered around one big ocean know as Panthalassa. A sea called
Thethys divided the Pangaea into two huge landmasses: Laurentia and
Gondwanaland. The landmasses consisted of the SIAL and the ocean
had a SIMA - heavier base.
The drift started 200 million years ago and the continents started to break
up and drift away from each other.
They moved equator wards due to the interaction of forces of gravity and
westwards due to the tidal currents and finally over thousands of years
formed what the continental masses look like today
Many landforms such as the Himalayas were created due to this continental
drift. Himalayas were created as the Indian Subcontinent was separated from
the Australian continental mass and drifted into the European/Asian
continent.
Evidence:
Apparent Affinity of Physical Features - they fit into each other -
example South America and Africa fit perfectly into each other if the
Atlantic ocean was removed
Presence of Ice Sheets - evidence of ice covering Falkland Islands (as
per the carbonferous plant fossils) means these landmasses were
closer together at sometime
Botanical Evidence
3. Sea Floor Spreading
Describes the Movement of oceanic plates relative to each other
According to this theory, the intense radioactive heat inside the earth crust
beneath the oceans seeks escapes and gives rise to the formation of
convention currents in the mantle. Whereever a rising limb of these
conventional currents form, oceanic ridges are formed, on the sea floor and
wherever the failing limbs meet, the deep trenches are formed.
Plate Tectonics:
The lithosphere is broken into a number of plates or sections, each of which is capable of
individual movement over the aesthonesphere carrying both continental and oceanic crust
alike.

The movement of this crustal plain causes formation of various landforms and is the
principal cause of all the earth's movements. These plates are borne along a worldwide
system of ocean trenches, ocean ridges, great faults and active fold belts. The plates
migrate away from the ridges and ultimately collide into them again.Hence, they meet
each other at the following:
Evidence:
1. The continental crust is older and the oceanic is younger indicating that there is
effective sea floor spreading along the oceanic ridges, which are plate margins.
2. The fact that all regions near plate boundaries are volcanic in nature
Types:
-Divergent Edges, plates move away from each other and crust is formed due to eruption
of magma. Hence it's a constructive edge
-Convergent Edges, destructive edge as the plates meet head on and collide to create
folding, and crumpling of the land.
-Transcurrent Edge, the plates move past each other without much action

Six Major Crustal Plates:

American
Eurasian
African
Indo-Australian
Pacific and the Antartic

Others are minor ones.

TSUNAMI:
Tsunamis are large waves (or a series of ocean waves) created in the oceans due to
geaological disturbances like earthquake, volcanic eruption, lanslides and rarely by hitting
of meteorite on the surface of the ocean). The series of traveling waves can be as tall as
100 meters with speeds ranging from 350-850 Km/hr. These can cause substantial havoc
to life on the coastal areas and loss to life and property.

Some Tsunamis do appear as tidal waves however these are not tidal waves but
seismic waves created by the acitivity of earthquakes, as opposed to tidal waves
which are created due to the gravitational pull of moon or sun and planets.
Warning Systems
The Indian Ocean is not prone to Tsunamis. Only two have occured in this
ocean including one in Dec. 2004.
India has been a leader in the initiative to develop early warning system for
Tsunamis
The Deep Ocean Assessment and Reporting System (DOARS) has been set
 up at depth of 6000m to quickly detect the movements in sea floor with help
of sensors
This plan of network would work with Indonesia, Thailand, and Myanmar, to
calculate the intensity and timings of tsunamis.
State of the Art National Tsunami Early Warning Center was set up in 2007.

ROCKS:
Earth's Crust:

98% is composed of right elements: oxygen (46.60%), silicon (27.72%), aluminium,

iron, calcium, sodium, pottassium and magnesium and others. (OSA, ICS, PMO)
These elements are rarely found exclusively and combine with others to form
minerals found on the earth's surface. Hence, mineral is a naturally occuring
inorganic substance having an orderly atomic structure and a definite chemical
composition, and physical properties.
Source: Basic source of minerals is the hot magma from the earth's interior. When
the magma cools on the surface or inside the surface, its minerals appear and they
further solidify to form rocks. Minerals such as coal, petroleum, and natural gas are
organic substances found in solid, liquid and gaseous forms.
Characteristics: Color, Shades, Streaks, Structure, Transparency, Hardness,
External crystal form, cleavage, fracture, lustre, SPECIFIC GRAVITY - the ratio
between the weight of the given object and the weight of an equal volume of
water
Major Minerals: Feldspar (silicon and oxygen) - most common, Quartz (silica),
Pyroxene (calcium, al, magnesium, iron and silica) - commonly found in meteorites,
Amphibole (alum, cal, silica, iron, magnesium), Mica (calcium, magnesium,
pottasium, iron), Olivine (magnesium, iron and silica)
Metallic Minerals
Precious metals - gold
Ferrous Metals - iron
Non Ferrous Metals - copper, lead, zinc, aluminium
Non-Metallic Minerals:
Sulphure, Phosphates, Nitrates - cement is a mixture of non-metallic
mixtures

Formation:

Rocks are compositions of one or more minerals. The earth's crust is composed of
rocks.
Can be hard or soft or in different colours and their characteristics also depend
upon the composition of minerals in them. However, they do not have a regular
composition of minerals in them. Petrology is the science of rocks.
Example: Granite is hard and soapstone is soft, Gabbaro is black and quartzite can
be milky white.

Types:

Igenous Rocks
Igneous rocks are formed by the cooling down of hot magma released from
 the interior of the earth. They are hence known as primary rocks.
If cooling happens on the surface and is very quick, they form smaller and
smoother crystals while when the cooling happens slowly inside the earth's
surface, they form larger crystals.
Two types:
Plutonic Rocks
Igneous rocks formed at some depth in the earth’s crust.
These are cooled rocks formed of large crystals due to slow
cooling down in the interior of the earth.
Eg: Granite, Diorite, and Gabbro
Volcanic Rocks
Molten rocks poured out of volcanoes as lava and than solidified
rapidly on the earth’s surface and the crystals are small due to
rapid cooling.
Eg: Basalt, Deccan plateau in India

Sedimentary Rocks (stratified rocks)

Rocks on the surface of earth are exposed to denundation which causes
breaking up of these rocks into finer particles.
These sediments or particles are carried away by various exogenous
agencies and settle down and form rocks knows as sedimentary rocks.
This process is called lithification.
May be formed due to action of glaciers, water, streams, winds or even
animals.
These are non-crystalline in nature and often contain fossils
We see a number of layers in these sedimentary rocks like shale and
sandstones.
Mechanically formed - Formed due to the accumulation of materials
derived from other rocks which have been cemented together.
Eg: Sandstone
Chemically formed - Such rocks are precipitated chemically from
solutions of one kind or another. Eg: potash and nitrates
Organically formed - Formed from the remains of living organisms such
as corals, shellfish, from the hard shells left behind by them. eg:
limestone and chalk.
Organically formed can be of two types: Calcareous type —
formed due to calcium deposit from shells etc. and
Carbonaceous types — formed by organically deposited
vegetative matter in swamps etc. Eg: Peat, lignite, coal etc.
Metamorphic Rocks
These rocks are formed under the action of PVT - Pressure, Volume and
Temperature
Already consolidated rocks go under recrystallization and reorganisation due
to PVT, hence resulting into the formation of metamorphic forms
Thermal Metamorphism - under heat (chemical alteration takes place)
Contact Metamorphism - rocks come in contact with hot lava
Regional Metamorphism - rocks in vicinity of high temperature of hot
lava
Dynamic Metmorphism - under pressure (no chemical composition changes
here)
Eg: Granite under pressure become Gnesis, Clay and Shale under Pressure
 become Schist, Sandstone under heat becomes Quartzite, limestone into
marble, coal into graphite
Major mountain chain periods
Major mountain chains were formed in one of the 9 mountain building
movements in the earth’s crust.
Main mountain ranges of today, the Alps, Himalayas, Andes and Rockies
were formed in the Alpine age around 30 million years ago

Types of Mountains:

1. Fold Mountains
Formed due to folding or compressing of layers of the earth.
Different types of folds: anticlines, synclines, asymmetric fold, overfold,
recumbent fold, nappe
2. Block Mountains
When the earth’s crust bends folding occurs, but when it cracks faulting
takes place.
Faulting may be caused by tension or compression, forces which lengthen
or shorten the earth’s crust, causing a section of it to subside or to rise
above the surrounding level.
This results in horsts or block mountains and their counterparts graben or rift
valleys to come into being
 3. Volcanic Mountains
These are volcanoes formed due to ejection of volcanic material
Formed around a vent
Eg: Mt. Fuji in Japan, Mt. Mayon in Philippines
4. Residual Mountains
Evolved by denudation
Some areas get denunciated but very resistant areas within them do not get
denunciated and hence form a residual mountain
Eg: Mt. Manodnock in USA and parts of Deccan plateau in India

Types of Plateau

Plateau is elevated upland with extensive level surfaces, and usually descended
steeply to the surrounding lowland.
Raised table-like platform landscape that stretches hundreds and thousands of
miles.
Types:
Tectonic — formed by earth movements which cause uplift and are of large
size and uniform altitude
Tibetan Plateau
Deccan plateau
Volcanic
Deccan plateau
Dissected Plateau
These are plateaus that are formed due to continuous weathering and
erosion by running water, ice and winds. High and extensive plateau
are gradually worn down and their surfaces made irregular. These are
known as dissected plateaus.
Eg: Scottish highlands
Plateaus are rich in mineral resources around the world.

Types of Plains

Plains are flat lowlands, either level of undulating.

 Generally fertile and highly cultivated.
Eg: Indo Gangetic plains, Yang-tze plains in China
Types:
Structural plains
These are structurally depressed areas of lands that form some of the
most extensive lowlands in the world.
Eg: Great plains of Russia, Great plains of USA and central lowlands of
Australia
Depositional Plains
Formed by deposition of materials by rivers flowing through the area
and also through wind and other agents.
Eg: Ganga Plains, Hwang Ho Plains in China
Erosional Plains
Created by the erosional work of rivers, glaciers etc. in leveling the
surface of the earth.

Rock Cycle

Rocks constantly undergo change due to the PVT factors and transform from
one form to other.
Sedimentary rocks in the interior of the earth (carrried downwards due to
subduction process) melt into molten lava under great temperature and
pressure and get transformed to igneous rocks which may get crystalised at
earth's surface or in the interior. These igneous rocks may get exposed to the
exogenous factors on the earth's surface and get transformed into
sedimentary rocks again. The igneous rocks may also turn into metamorphic
rocks due to their exposure of PVT factors causing recrystallisation or
reorganisation due to thermal and regional factors.
Hence, Igenous Rocks are primary forms and others are formed from them.
Atmosphere of the Earth:
Atmosphere composed of gases, water vapour, and dust particles.
Nitrogen, Oxygen, Argon, CO2, Neon, Helium, Krypto, Xenon and Hydrogen

Green House Effect:

Casued by CO2, which traps the earth's heat by allowing sun's rays to enter the
atmosphere but by not letting the incoming heat escape. It absorbs some of the
heat that gets reflected back from the earth's surface and reflects the rest back into
the atmosphere of earth.

Water Vapour: More in the tropics than the poles. Also absorbs insolation from the sun
and preserves the earth's radiated heat. Contributes to the stability and instability of the
air.

Dust Particles: Act as hygroscopic nuclei around which water vapour condenses to form
clouds

Structure of the Atmosphere:

Density is highest near the surface of earth and then decreases

TSM(I)TE
Troposphere
First layer of the earth's atmosphere and is thicker along the tropical
areas and thin along the poles. The thickness is more at the tropics
because the strong convectional currents pass the heat to a much
higher altitude here.
Layer contains large amounts of dust particles and water vapour
Temperature decreases with increasing altitude in this layer
Stratosphere
Ozone Layer
Temperature increases with increasing altitude in this layer because of
the presence of ozone layer
Mesosphere
Shooting stars burn here
Temperature decreases with increasing altitude in this layer
Ionosphere
Lies above the mesopause
Contains electrically charged particles which deflect the radio waves
from earth
Thermosphere
Exosphere
Earth’s four spheres: Hydrosphere, Atmosphere, Lithosphere and Biosphere

The three abiotic spheres interact together to form a biotic sphere — biosphere.
INSOLATION, HEAT BUDGET, TEMPERATURE:
INSOLATION:

Incoming Solar Radiation into the earth is known as insolation and causes heating
of the earth
It is received in the form of short wave lengths which are electromagnetic in nature
These short waves and UV rays are partly absorbed by the atmosphere and the
reflected rays from the earth's surface are long-waves.
Energy Recieved: 2 calories per sq. cm per minute.
Insolation most at the equator and least at the poles. Insolation received in the
Northern Hemisphere is more along the tropics in winter and summer than along
higher latitudes. More insolation over land than over the oceans.
Factors Affecting Distribution of Insolation, i.e. amount of heat reaching earth's
atmosphere:
The Rotation of Earth on Its Tilted Axis
Causes Seasons
The Angle of Inclination of Sun's Rays
 Since the earth is spherical in shape, different latitudes get different
angles of suns rays
The higher the latitude the less is the angle of the suns rays with that
of the land resulting in slant sun rays.
Length of the Day
During different solstices, the length of the day varies and hence the
temperature also changes
The Transparency of the Atmosphere
More transparent at the poles (hence more reflection) and less at the
equator (more water vapour and dust particles - hence more
absorption)
The Configuration of the Land
Two sides of a hill may have different temperatures due to difference in
fall of sun rays on the sides. One side may get more insolation as it
may be facing the sun during the day and the other side may be in the
shadow area hence having lower temperature
Land-Sea Differential
Reflection by land is more and the depth of insolation is less than that
of oceans, Land absorbs heat faster and loses it faster as well, while
the oceans do the opposite
Prevailing Winds
Ocean Currents
Altitude
This energy varies on the earth's surface and atmosphere due to earth's proxmity
with the sun
During July, the earth is FARTHEST to the sun called the Apihelion (Northern
Hemisphere)
During January, the earth is CLOSEST to the sun called the Perihelion
(Northern Hemisphere)
Thus it is possible to see that Earth's distance from the sun does not cause
the season to change. This is mainly due to other factors that mask this
change. These factors are land and sea distribution, and atmospheric
circulation.
Instead, Earth's seasons come and go because Earth does not rotate with its
axis exactly upright with respect to the plane of our world’s orbit around the
sun. Earth's axial tilt is 23.5 degrees. This puts the Sun farther south in
December and January, so the north has winter and the south has summer.
Thus winter falls on that part of the globe where sunlight strikes least directly.
Summer falls on that part of the globe where sunlight strikes most directly.
Earth's HEAT OR ENERGY BUDGET:

Earth receives sun's rays on its surface and atmosphere. This process is known as
insolation and it is the major factor in determining the temperature and heat levels
of the earth's atmosphere.
Definition: The Sun's radiation recieved by the earth's atmosphere is either
reflected back into the upper layers of the atmosphere, or retained within the
earth's lower layer i.e. troposphere. Through this process, earth maintains its
temperature levels and heat, and transfer the excess energy to the space while
maintains appropriate energy or heat levels within the atmosphere. This system is
known as Energy or Heat Budget.
Earth's Atmosphere recieves and disperses the sun's radiation in two forms: short
wave radiation and long wave radiation.
Short Wave Radiation is recieved through the atmosphere and approximately 35%
of the radiation is reflected back or absorbed by the atmosphere before reaching
the surface, while approximately 65% of the radiation reaches the earth's surface.
Out of the 65% that reaches the earth's surface, approximately 14% of the
radiation is absorbed by the atmosphere and 51% is absorbed by the earth.
The Earth reflects back 51% of this radiation in form of long waves or
terristial waves.
Of these 17% is reflected back directly to the space
34% is absorbed by the atmosphere
Hence 48% of the radiation is absorbed by the atmosphere: 34% from
terristial radiation which is reflected from the earth and 14% directly from the
insolation
Therefore, total radiation returning from the earth to the atmosphere is 48%
from terristial reflection and direct insolation, plus the 17% from the direct
reflection from the earth. Making this a total of 65% reflected back to the
atmosphere from earth, hence balancing the 65% that was received from the
insolation that was reaching the atmosphere.
This explains why the earth never warms up or cools down despite
huge transfers of heat that take place
Latitudnal variation is seen for heat surplus or deficit - surplus at tropics and
deficit along the poles.
TEMPERATURE:
The interaction of insolation with the atmosphere and earth's surface creates heat which
is measured in the terms of temperature.

Importance:

1. Temperature governs the amount of water vapor in the air, and hence the moisture
carrying capacity of air.
2. Temperature governs the evaporation and condensation, and hence the stability of
the atmosphere.
3. It governs the cloud formation and precipitation.

Factors controlling Temperatures in the atmosphere:

Latitude of the Place

Insolation varies due to the latitude and so does the temperature
Altitude of the Place
The temperature is higher near the lower altitudes because it's closer to the
long wave or terrestrial radiation reflected back from the earth's surface
Ocean Currents and winds
Warm ocean currents or cold ocean currents in the vicinity of the land mass
Example: The Gulf Stream that becomes the North Atlantic Drift has a
warming impact on UK’s weather or western Europe keeping ports ice-free.
However, Labrador current, the cold current in the same latitudes off north-
east coast of Canada results in frozen area due to its cold nature.
Continentality or Distance from the Sea
Sea gets heated slowly while the land gets heated faster. Therefore, the
variation of temperature in sea is lower than that in land. The places near the
sea come under the moderating effect of the sea
Local Aspects — such as slope, shelter and aspect
The south facing slopes are more sunny vs. the north facing "sheltered
slopes"

Important: Variation of temperature along the isotherms in Northern and Southern

Hemispheres
Variation of temperature is MUCH MORE in the Northern hemisphere because of
the presence of far more land masses compared to the southern hemisphere. - the
land mass impact on insolation

This is shown by the fact that in January, isotherms deviate more in the northern
hemisphere from one latitude to the other as compared to the southern hemisphere.
Example: In the North Atlantic ocean, due to the presence of Warm Ocean currents
like the Gulf Stream and the North Atlantic Drift, the isotherms bends towards the
North, but it bends sharply southwards over European landmass. This is much
more pronouned in the Siberian plains.
In the southern hemisphere, the isotherms are more or less parallel to the latitudes
and the variation in temperature is far less.
ATMOSPHERIC CIRCULATIONS AND WEATHER SYSTEMS:

Air expands when it gets heated and it compresses when cooled down. This expansion
and compression in air creates differences in air pressure or atmospheric pressure which
further causes circulation of air in the atmosphere from high pressure to low pressure
areas.

Winds: Horizontal flow of air from areas of high to low pressure. Wind redistributes
the heat and moisture in the atmosphere.
Clouds: Vertical rising of moist air which forms clouds and then to bring
precipitation
Pressure decreases rapidly with height.
World Distribution of Pressure:
Near the equator, the air pressure is low and hence it is know as the area of
Equatorial Lows
Along the 30 Degree South and North, the air pressure is high and hence this
is called as the area of subtropical highs
Along the 60 Degree South and North, the air pressure is low and hence this
is called as the area of subpolar lows
At Poles, the air pressure is High and hence known as polar highs
These pressure belts oscillate with the movement of the
They move southwards in the winters and northwards in the summers
- ITCZ moves northwards over the Indian subcontinent during the
summers
Forces Affecting Velocity of the Winds:
Pressure Gradient Force
The differences in the atmospheric pressure produces force. The rate
of change of pressure with respect to the distance is the pressure
gradient. The isobars are closer to areas where the pressure gradient
force is more.
Coriolis Force
Caused by the rotation of the earth. Deflects the wind to the right in
the Northen Hemisphere and to the left in the Southern Hemisphere.
More deflection when the wind velocity is more due to pressure
gradient or fricitional force.
This force is directly proportional to the angle of the latitudes, hence 0
at the equator and maximu at the poles
Frictional Force
Frictional force is created when the winds pass horizontally close to
the surface of the land and seas
It results in changes in velocity of the winds
It is more on the surface of land while less on the surface of the seas
where it is smooth
Creation of Tropical Storms
Happens as the coriolis force and the pressure gradient act perpendicular to
each other. The pressure gradient force is also perpendicular to the isobar.
The more is the pressure gradient, the higher is the velocity of the wind, and
hence the more is the deflection of the wind due to coriolis force.
In the low pressure areas, due to the perpedicular function of the winds, the
winds blows around the two forces in a circular motion. At the equator, there
 is no coriolis force, hence the pressure gradient is perpendicular to the
isobars, and hence it simply gets filled instead of getting intensified on
deflections. That's why there are no tropical cyclones at the equator.
General Circulation of the Atmosphere or the Winds:
The winds follow a general pattern of circulation in the atmosphere. This is
affected by:
1. Coriolis Force of Earth
2. The Pressure belts of the earth
3. The Shifting of pressure belts as they follow the sun
4. The latitudinal variation of atmospheric heating
5. The distribution of land and the oceans
Explanation of Wind System:
ITCZ and the Doldrums- Inter Tropical Convergence Zone lies at the
equator and it is the zone of low pressure belt across the equatorial
latitudinal belt.
This is known as doldrums by the sailors due to almost
complete absence of sailing winds in this region
The tropical trade winds convergence into this zone from the
higher pressure Subtropical Latitudes (also known as horse
latitudes).
Subtropical High Pressure Belt or the Horse Latitudes - The
subtropical high pressure belt is an area of high pressure around the
northern and the southern subtropical belts (i.e. in the 30 degree North
and 30 degree South latitudinal area). The Westerlies (originating from
the west) flow from this high pressure area towards the ITCZ or
doldrums, where low pressure belt is formed.
Subpolar Westerlies - Area of low pressure lies in the subpolar belt
i.e. in the 60 degree North and 60 degree south latitudes. The Polar
Easterlies (originating in the east) flow from the polar region towards
the subpolar low pressure belt.
Polar High - High Pressure belt formed at the poles
Process of Wind Movements
At the ITCZ, high insolation causes temperatures to rise and air to
expand, hence forming an area of low pressure. The cooled and
denser winds from the subtropical latitudes flows as winds towards
the low pressure ITCZ. This wind is known as trade winds or the
easterlies (originating in the east). The heated and expanded air at
the ITCZ rises above the earth's surface in the troposphere up to a
height of 14 kms. This heated air circulates towards the subtropical 30
degree North and South latitudes as it pushed by the incoming cooler
air from the surface in form of the trade winds. This circulation of air
upwards from the surface, between the low and the high latitudes is
known as a cell and the circulation in the 30 degree N and 30 degree S
region from the equator is known as the Hadley cell.
The reverse action takes place between the middle latitudes, i.e. the
subtropical latitudes to the subpolar latitudes. Westerlies, or the winds
originating from the west flow from the area of high pressure at the
subtropical latitudes towards the area of the low pressure at the
subpolar belts. These winds are known as westerlies and the cell is the
Ferrel cell
The cold winds flow from the area of high pressure at the poles to the
 area of subpolar belts. These winds are known as polar easterlies and
the polar cell is formed in this region.
These three cells set the pattern for air circulation around the world.
The transfer of heat from the lower latitudes to the high altitudes
maintains the general circulation. This general circulation also
creates the large and slow moving ocean currents. Oceans, in
exchange, provide energy and water vapour into the air.

LOCAL WINDS
Land and Sea Breezes:
Due to the differential heating of sea and land, the wind movements get affected.
During the day, the land gets heated faster, hence the winds blow from the cooler
and higher pressure gradient over the sea to the lower pressure gradient over the
land, hence bringing cool breezes to the land.
In the night, the land gets cooled faster and hence the winds blow from land to the
sea.
Mountain and Valley Winds
-During the day, the sloped of the mountain valleys get heated up and the expanded air
moves upslope, and to fill the resulting gap the air from the valley blows up the valley.
This is known as the valley breeze.
-During the night, the slopes get cooled down and the dense air descends into the valley
as the mountain wind. The cool air, of the high plateaus and ice fields draining into the
valley is called katabatic wind.
Air Masses

When air remains over a substantially large area and acquires the characteristics of
that area, it is called an airmass. Air masses are formed of air staying over large
areas (oceans or land mass) with homogenous climatic conditions for a long period
of time. The air acquire distinct characteristics of humidity and temperature from
the landmass or the vast ocean below it.
Five major areas where air masses are formed:
Warm subtropical and tropical oceans - Maritime Tropical Air Mass
Hot subtropical deserts - Continental Tropical Air mass
Very Cold high altitude snow covered areas of continents - Continental polar
air mass
Very Cold polar regions of arctic and anatartica - Continental Arctic air mass
Cold high latitude areas of the oceans - Maritime Polar air mass

Fronts
When two different air masses meet, the boundary zone between them is known as a
front. These occur mostly in the middle latitudes and bring abrupt changes to the
temperature and cause air to rise to form clouds and cause precipitation.

Warm Front, Cold Front and Occluded Front

Extra Tropical Cyclones

In the areas of middle and higher latitudes, the cold winds from the cold front and
the warm winds from the warm front create a system, which results in the extra
tropical cyclones.
In these latitudes, warm winds blow from the area of low pressure in the subtropical
region towards the cold front of the subpolar region. Hence, this warm air rises
above the cold front and the cold air from the subpolar region moves towards the
subtropical warm front underneath the warm air. This circulation of winds from the
warm to the cold front and vice versa creates anti-clockwise extra tropical
cyclones.
Difference between Extra Tropical and Tropical Cyclones:

Extra Tropical cyclones have a clear system of fronts while tropical cyclones don't.
Extra Tropical cyclones are spread over large areas and can generate over the land
or the sea while tropical cyclones are limited in geography and can only originate
over the oceans.
Tropical cyclones have much higher wind velocity and are more destructive.
Extra tropical cyclones move West to East and the Tropical Cyclones move East to
West.

Tropical Cyclones

Tropical Cyclones are powerful wind and precipitation systems that build over the
oceans or large sea areas and move towards the land and dissipate over it. Tropical
Cyclones bring high and destructive wind velocities, lot of rain and storm surges
over the landmasses they move towards.
Names:
Tropical Cyclones - Indian Ocean
Hurricanes - Atlantic Ocean
Typhoons - Western Pacific and the South China Sea
Willy Willies - Australia
Tropical cyclones originate over the warm topical oceans, intensify there and move
towards the land from East to West. The conditions required for the formation of
cyclones are:
Warm Temp. of over 27 degrees over the ocean
Large Sea Surface
Presence of the Coriolis Force
 Small Variations in vertical wind speed or Low Wind Shear
A pre-existing weak low pressure area
Upper divergence above the sea level system
Process - explain from the diagram

Amazing definitions and questions at:

http://www.rsmcnewdelhi.imd.gov.in/index.php?
option=com_content&view=article&id=20&Itemid=166&lang=en

Naming of Cyclones:
http://www.rsmcnewdelhi.imd.gov.in/images/pdf/cyclone-awareness/tc-names/tc-
names.pdf

Thunderstorms and Tornadoes

Thunderstorms are caused by large mass of heated air that rises up to create
 large cumulonimbus clouds. As these clouds rise up and reach an area of relatively
lower temperatures, the condensation process takes place and they release
immense amount of precipitation over the surface of earth. If they rise up to heights
of sub-below temperature levels, they cause hailstorms. If the air rising up is dry,
thunderstorms cause dust storms.
They are short-term and intense release of precipitation.
Later downdraft towards the earth brings cool air and the rain.
Sometimes, from these thunderstorms, spiraling air descends down like trunk of an
elephant with great force with very low pressure at the center, causing massive
destruction on its way. Such a phenomenon is known as Tornadoes. The
tornadoes over the sea are known as water sprouts.

Nice Notes: http://uw.physics.wisc.edu/~himpsel/107/Lectures/Cyclone.pdf

Other notes: Direction of wind in the low pressure area in the Northern hemisphere is
counter-clockwise due to the coriolis force.

MONSOONS AND THE EL NINO

WORLD CLIMATE AND CLIMATE CHANGES:

Koeppen's empirical system of climate classification is the most widely used and
accepted one.
He identified a close relationship between climate and the distribution of vegetation
on its basis.
He categorized the vegetation distributions on the basis of temperature and
precipitation.
Climate Changes:

Historically, climate has been consistent for long period of time (as we are
experiencing right now over the last 10,000 years), with some minor changes, but
there have been ages of warm and cold climates over these long periods as well.
These large changes and presence of hot and cold ages have been indicated by
presence of glacial deposits found in middle of the continents indicating
advancement of the glaciers, and hence different climatic periods.
Also indicated by rings of trees which indicate moist and warm periods.
Many Reasons for these large climatic changes. Major are:
Terrestial
Astronomical
Due to the sunspot activities
When sunspot increases, cooler and wetter weather takes place
Greenhouse Gases (GHGs)
1. CO2
2. CFCs or Cholorofluorocarbons - destroy Ozone
3. CH4 or Methane
4. N2O Nitrous Oxide
5. O3 or Ozone
Kyoto Protocol to decrease the amount of GHGs in the atmosphere

Rainfall:
Types of Rainfall:

Convectional
The air once it gets heated by extreme sun and heat, rises up in convection
currents. As it rises, it expands and loses heat and consequently
condensation takes place and cumulonimbus clouds are formed.
The rainfall takes place with thunder and lightening but does not long very
last.
Very common in areas which get intensely heated other during the day, as in
the tropics, or in the summer, as in temperate interiors.
Cyclonic or frontal rain
This type of rainfall takes place due to the convergence of two air masses
with different temperatures and other physical properties.
As cold air is denser, it tends to remain on the ground. Warm air rises up over
the cold air. In ascent, pressure decreases, the air expands, and cools and
condensation takes place and light showers called cyclonic or frontal rain
occur.
Caused as a result of cyclone that releases tremendous amount of
precipitation as the air mass rises up in and falls out through the
cumulonimbus clouds
Orogenic / Orographic or Relief Rain
Causes due to land relief.
When a saturated mass of air comes in contact with land mass (mountain), it
is forced to ascend and it rises. This causes it to expand and condensation
takes place, causing rain on the windward side of the mountain.
Eg: Assam Hills
 Rainfall Across the World
More in the coastal areas and decreases as we go from the equator towards
the poles
More rainfall over oceans than on the landmass
Between the 35 degree and 40 degree North and South latitudes, the rainfall
received on the eastern margins of the continents is more and decreases
towards the west.
However, in the higher latitudes of 45 degree and 60 degree South and North
of the equator, the rainfall received on the Western margins of the continents
is more due to the flow of the westerlies in this direction.
Hence more rainfall along the windward side of the western coastal areas of
the world , near the equator, coastal areas of the monsoon zone.
Central Parts of the Tropical Continents and the Eastern and interior parts of
the temperate lands receive 50-100 cm of rain.
Interior of the continents receive moderate rainfall of 100-200 cm. Same for
the other coastal regions of the world. Areas in the rain shadow zone of the
continents and near the poles receive low rainfall

WATER (OCEANS)

Watercycle or the Hydrological cycle

Condensation
Precipitation
Evapotranspiration
Ground Water
Ice Caps
Sublimation
OCEAN FLOOR
Divisions:

The Continental Shelf

Continental shelfs of north west Europe of hundreds of miles, but those of
North America’s Pacific coast are only a few miles wide.
Formed by three main processes:
Melting of ice turning into water from the poles increasing volume
of water in oceans and submerging part of the continent
Waves from the oceans degrading the land mass of the continents to
form the shelf
 The rivers flowing into the ocean with massive amounts of sediments
which are deposited to form continental shelf
Importance:
Most plankton growth activity occurs here which provides food to
many fishes both in shallow and deep oceans
Richest fishing grounds of the world are found in continental shelfs
Eg: Grand Bank off Newfoundland, the North Sea (next to UK, right
side) and the Sunda Shelf (the Philippines islands and the Indonesian
islands)
The Continental Slope
Abrupt slope next to the Continental Shelf
The Deep Sea Plain (Abyssal Plains)
Lying 2 to 3 miles down the sea level, these are undulating plains covering
almost 75% of the ocean’s floor.
This consists of plateaus, ridges, trenches, basins and oceanic islands that
rise above the sea level.
Ridges, Hills, Canyons, Trenches, Guyouts (flat top submerged mountains),
Atolls (low islands consisting of coral reefs surrounding a central depression
in the tropical seas)
The Oceanic Deeps
Sudden, deep plunges into the ocean.
Not necessarily in the middle, but rather close to continental mass.
Eg: Mariana trench
Temperature of Ocean Waters:
Thermocline: Layer in the ocean deep from where the temperature declines rapidly with
increasing depths. (500m-1000m deep)

Salinity of oceans:
Affected by the following reasons:

1. Amount of fresh water added into the ocean - more fresh water pouring means less
salinity.
 Eg: Polar Regions where fresh ice is thawing into the ocean or equatorial
regions where there is high amount of rainfall and nearby lot of rivers are
emptying into the ocean such as Ganges, Amazon etc.
2. Rate of Evaporation: The water fringing the High Pressue Belts of the Trade Wind
Deserts, between 20 and 30 N and S have high salinity because of high rate of
evaporation caused by high temperature and low humidity. The temperate oceans
have lower salinity due to lower temperature and lower rate of evaporation.
3. Ocean Currents - Ocean currents lead to constant mixing of waters and travel of
water, causing the mixing of minerals and hence moderating salinity in it. Waters in
enclosed seas like the Red Sea, Caspian sea etc. are high in mineral content
due to absence of currents and mixing.
4. Temperature, Density and Salinity of water are interrelated. Hence, any changes in
temperature or density affect salinity
5. Winds - transferring water to different areas and hence impacting salinity
6. Depth of the water- on the surface, salinity depends on the amount of evaporation
and precipitation, but it is largely constant in deeper areas of the oceans

Highest salinity recorded between 20 degree North and 30 degree North, why?

*Over 80% of ocean water has temperature between 35 F and 40 F (1 degree c - 4 degree
c)

Ocean Currents
Forces guiding the movement of ocean currents:

1. Winds
Between the equator and the tropics blow the Trade winds which move
equatorial waters polewards and westwards, and warm the eastern coast of
the continents.
For example: the North-East Trade Winds move the North Equatorial
Current and its derivatives, the Florida Current and the Gulf Stream
Drift to warm the southern and eastern coasts of USA.
Similarly, the South Equatorial Current which wars the eastern coast of
Brazil as the warm Brazilian current.
In the temperate latitudes, flow the Westerlies, that flow the water
northwards and towards the east. Hence, the warm Gulf Stream is driven to
the western coast of Europe as the North Atlantic Drift.
Similarly in the Southern Hemisphere, the Westerlies drive the West Wind
Drift equator wards as the Peruvian Current off South American and the
Benguela Current off Southern Africa.
The planetary winds are the most important factor that impact the
movements of ocean water and dominate the movement of ocean currents.
The most striking example of this is the change in direct of monsoon winds
causing the complete change of current in the Indian ocean. (which
change from North East direction in the winter to South West direction in the
summer).
2. Insolation
Insolation causes differences in temperature. The equatorial water is higher
in temperature and thus more light and travels on the surface of ocean. Th
pole water is cold and hence sinks at the bottom slowly.
3. Land mass
 Obstructs and diverts a current. For example, the tip of southern Chile
diverse parts of the West Wind Drift northwards as the Peruvian or Humboldt
current.
4. Coriolis Force/ Earth’s rotation
Has a rightwards deflection to the ocean water in northern hemisphere and
leftwards deflection in the southern hemisphere.
Therefore, the Canaries Current deflects rightwards in the Northern
hemisphere and the West Wind Drift and the Peruvian current in the leftwards
direction in the southern hemisphere.

**Sargasso Seas — middle of the Atlantic Ocean where there is no current and all the
floating sea-weed gathers.
—this sea weed collection in not distinctive in southern hemisphere.

Effects of Ocean Currents:

1) Fishing - are found generally where cold and warm currents meet as mixing of cold
wand warm currents results in oxidation of the water causing great plankton growth in
these regions
2) West Coasts of Continents in the Tropical and Subtropical Northern and the Southern
Hemisphere (except close to the equatorial regions) mostly have cold currents, hence they
result in cooler and drier climate in these regions.
3) West Coast of Continents in the Higher latitudes and near the equator have warm
currents, hence causing distinct marine climate - cool summers and mild winters with
narrow annual range of temperatures.
4) Warm currents flow parallel to the continents in the tropical areas, causing warm and
rainy climates.
Other Water Movements of Ocean
Waves

Waves are caused by the energy from the winds along the ocean surface. Waves
are not water, but energy. Water simply circulates with the wave energy as the wind
flows across the oceans.
Speeds of waves decreases as they approach the coastal areas due to continental
shelf friction.
Tides

Tides are periodical rise and fall in the sea level, generally once or twice a day,
caused due to the gravitational force of the moon and the sun. Another force
responsible for tides is the centrifugal force that acts against the gravitational force
to induce tides. Hence, together gravitational pull and centrifugal force cause
tides.
Two bulges in the water takes place on the surface of the earth as tides. One bulge
is caused by the gravitational pull of the moon or sun in the surface of the earth
 facing the moon or the sun.
The other bulge is caused by the centrifugal force on the opposite side of surface
from the moon/sun.
Tidal bulges are higher on the wide continental shelves.
Tidal Currents: When the tides are channeled into bays and estuaries or islands
they are called tidal currents.

Types of Tides:
Based on Frequency of the tide
1. Semi-diurnal tides: two high tides and two low tides during the day
2. Diurnal Tides: There is only one high and one low tide during the day
3. Mixed Tide: Tides having variations in heights are known as mixed tides

Based on Heights - i.e. due to the position of moon and sun

1. Neap Tides
When the sun and the moon are positioned at right angle to each other, the neap tides
take place as the sun's gravitational pull counteracts the moon's gravitational pull. These
tides are lower in height than the spring tides.

2. Spring Tides
When the sun and the moon are positioned in line with each other and the earth, the
spring tides take place as the sun's gravitational pull acts and the moon's gravitational
pull also acts to create high and more varying tides. These occur twice a month.
 Once a month, when the moon is closest to the earth (perigee), the pull is high and
extraordinary tides with large highs and lows are recorded. At apogee (2 weeks
later), the moon's pull is limited hence the tides are not varied
When the earth is closest to the sun (perihelion) the pull is high and extraordinary
tides with large highs and lows are recorded. Opposite for aphelion.
The time between the high tide and the low tide when the water level is falling is
called an Ebb and when it is rising is called the flow or flood.

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Islands
Types of Islands

1. Continental Islands
These are the islands formed due to separation from the main
continental land.
Generally separated by a shallow lagoon or a deep channel. This separation
is due to subsidence of some part of the land or to a rise in sea level, so the
lowland links of the continent are submerged by the sea.
Types of Continental Islands:
Individual Islands
These lie just outside the mainland, very much associated with
the characteristic features of the mainland of which they were
once part of.
Examples: Madagascar, Sri Lanka, Tasmania, Formosa (Taiwan)
Archipelagoes or Island Groups
Comprise of group of islands of various sizes and shapes. Eg:
British Isles, Balearic Islands of the Mediterranean
Festoons or Islands Arcs
The islands form an archipelago in the shape of a loop around
 edge or the mainland, marking the continuation of mountain
ranges which ca be traced on the continent.
Eg: East Indie, Kurile Islands, other arcs of the pacific ocean
2. Oceanic Islands
Small islands present in the midst of the ocean.
No connection with the mainland whatsoever and may be hundreds and
thousands of miles away
Flora and fauna unrelated to the continents
Eg: Galapagos Islands
Types of Oceanic Islands:
Volcanic Islands
Many islands in oceans are topmost parts of the cones of
volcanoes that rise from the ocean bed.
Eg: Mauna Loa in Hawaii, Mauritius and Reunion Islands in the
Indian Ocean
Coral Islands
Very low and emerge just out of water surface
Formed by activity of various coral species, these are found
both near the shores and in the midst of the oceans.
Eg: Marshall Islands, Bermuda in the Atlantic, Laccadives and
Maldives of the Indian Ocean

Coral Reefs

Coral reefs are distinct and peculiar marine landforms formed due to the calcium
carbonate secretion of various marine organisms such as coral polyps, calcareous
algae, shell-forming creatures and lime-secreting plants that live in large colonies.
These calcareous species grow in great numbers just below the water level. Polyps
are the most abundant and important ones and each polyp resides in a cup of coral
and helps to form coral reefs.
When they die, their limy skeleton are cemented into coralline limestone.
Coral reefs are the result of a mutually beneficial relationship between the polyps
and tiny single celled algae called zooxanthellae that live in the tissues of the
polyps.
Importance of Corals
They help moderate atmospheric temperatures by removing CO2 from the
atmosphere
They act as natural barriers to the coastlines and protect 15% of the world’s
coastlines from erosion.
They provided habitat for 25% of the world’s marine life.
They produce about 10% of the world fish catch from the sea and 25% of
fish catch in the developing countries.
Support tourism as well.
Coral Bleaching
It occurs when stresses such as increased temperature cause the algae,
upon which corals depend for food, to die off, leaving behind a white
skeleton of calcium carbonate.
Another threat is the increasing acidity of ocean water as it absorbs some of
the CO2 produced by the burning of carbon-containing fossils fuels. The
CO2 reacts with ocean water to form a weak acid, which can slowly dissolve
the calcium carbonate that makes up the corals.
Conditions necessary for reef-building are as follows:
Water Temperature:
Most not fall below 20 degree celsius.
Hence the corals are limited to tropical and sub-tropical zones only
Absent in western coasts of the continents due to cold water currents
and upwelling of cold water
Depth of the Water:
Should not exceed 180 feet because beyond this depth, sunlight
becomes too faint for photosynthesis to take place.
Water Quality:
Should be saltish and free from sediment. Corals survive best in
moving water of the oceans well away from silty and muddy coast.
They develop best on seaward side of the reef where constantly
moving waves, tides, and currents maintain supply of clear,
oxygenated water.
Types of Reefs:
Fringing Reef
A fringing reef is a coralline platform lying close to the shore extending
outwards from the mainland.
Could be separated from the shore by a shallow lagoon.
It is widest when fringing a protruding headland but completely absent
when facing mouth of a stream.
The outer edge grows rapidly because of the splashing waves that
continuously renew the supply of fresh food.
Barrier Reefs
A barrier reef is separated from the coast by a much wider and deeper
channel or lagoon. The reef is primarily submerged. Where it rises
above water, sand accumulates above it and hence not
much vegetation growth.
The barrier reefs have several gaps to allow water to return to open
ocean.
Eg: Great Barrier Reef off Queensland Australia.
Atolls
Similar to barrier reefs except that they are circular in shape and
enclose shallow lagoon without any land in the centre.
The encircling circle is usually broken at a few places.
Eg: Suvadiva in Maldives
Origin of Coral Reefs:

Most widely accepted theory given by Charles Darwin.

Known as the subsidence theory, it assumed that all coral reefs began as
fringing reefs around an island or the topmost portions of extinct volcanoes
that stood above the ocean bed.
Due to general downwarping of the earth’s crust, the islands gradually
subsided and the coral continued to grow upwards to keep pace with
subsidence.
The growth was more aggressive on the outward edges due to better living
conditions for the corals, and hence the barrier reefs, with a lagoon between
the island and the reef emerged.
Later, when the island completely submerged, the atolls were formed.
Glacial Control Theory
Given by RA Daly, the theory hypothesizes that at the time of ice age, the
water was too cold for any corals to survive. With marine erosion, the islands
were degraded and lowered by erosion. Overtime, as water became warmer,
 the locked up water in the ice sheets was released and these low lying
islands were submerged.
On these wave-planed platforms, corals began to grow upwards at the rate
of a foot in a decade to keep pace with the rising water.
Coral reefs, where islands still project above sea level, and atolls were thus
formed.

Coastal Landforms
Wave

Most powerful agent of marine erosion.

The water that rushes up to the beach and hurls rock debris against the land is
termed as swash.
The water sucked back and retreats as backwash.
Undertow: This is the offshore drift that flows near the bottom away from the shore.
This exerts pulling effort which can be dangerous for swimmers.
Erosional action of waves and other agents:
Corrasion
Attrition
Hydraulic action
Solvent action
Coastal features:
Cave, Arch, Stack and Stump
Gluops and Geos
The occasional splashing of the waves against the roof of a cave may
enlarge the joints when compressed air is trapped inside. A natural
shaft is thus formed which may eventually pierce through the surface.
This is known as a gloup or blow hole due to the sound of the water
going through it.
Eventually, this shaft enlarges and collapses due to pressure of the
overlying rock. The resultant think creek is known as geos.
A gluop:
 Depositional Features of Coasts
Beaches
Spits and Bars
Marine Dunes and Belts
Types of Coasts
Coastlines of submergence
These are formed due to the sinking of the land or the rise of the sea
level.
Types: Ria, Dalmatian or longitudinal, fiord coasts, estuarine.
Coastlines of emergence
These are formed due to the uplift of the land or fall of the sea level.

MAJOR INDUSTRIES OF THE WORLD, LOCATION and FACTORS

Factors Affecting Location of Industries Across the World:

1. Raw Material Supply

Nature of the raw material decides the location of industry near the source of
raw material or not affected by the location of the raw materials
Example, weight losing manufacturing industries like Cement, Sugar and iron
smelting, Weight Gaining: Baking, better to be near market
2. Power and Energy Resources
Energy intensive industries like aluminium and polythene are located near
cheap power resources
3. Labour Supply
Continuous and cheap labour supply is important. Relocation, though
 common, can be expensive
4. Means of Transportation and Communication
Play a role in bringing the raw material for processing to the factory and then
taking finished products to the market
Example: Hooghly river provides cheap waterways for transport of Jute,
hence a lot of Jute industries are based across the Hooghly river
5. Proximity to the Market
Some industries are located close to large urban centers to develop large
markets for their produce
6. Other Factors - financial capital, climate, government incentives
Government subsidies, price controls, and low capital availability help
industries.

Weber's theory - "least cost principle" which is used to account for the location of a
manufacturing industry