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Geomorphology

 

Most of the knowledge we have about Earth’s deep interior comes from the fact that seismic waves penetrate the Earth and are recorded on the other side.  Earthquake ray paths and arrival times are more complex than illustrated in the animations, because velocity in the Earth does not simply increase with depth. Velocities generally increase downward, according to Snell’s Law, bending rays away from the vertical between layers on their downward journey; velocity generally decreases upward in layers, so that rays bend toward the vertical as they travel out of the Earth. Snell’s Law also dictates that rays bend abruptly inward at the mantle/outercore boundary (sharp velocity decrease in the liquid) and outward at the outer core/inner core boundary (sharp velocity increase). 

5. World Geography Part 1 UPSC Notes | EduRev

 

Major Points to remember about P S and Love waves

  •  P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station. 
  • The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.
  • P waves are also known as compressional waves.
  • S wave or secondary wave, which is the second wave you feel in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium.
  • Travelling only through the crust, surface waves are of a lower frequency than body waves, and are easily distinguished on a seismogram as a result.

 

Earth’s Layers – Earth’s Composition

The Crust of Earth

It is the outermost and the thinnest layer of the earth’s surface, about 8 to 40 km thick. The crust varies greatly in thickness and composition – as small as 5 km thick in some places beneath the oceans, while under some mountain ranges it extends up to 70 km in depth.

The crust is made up of two layers­ an upper lighter layer called the Sial (Silicate + Aluminium) and a lower density layer called Sima (Silicate + Magnesium).The average density of this layer is 3 gm/cc.

The Mantle of Earth

This layer extends up to a depth of 2900 km.

Mantle is made up of 2 parts: Upper Mantle or Asthenosphere (up to about 500 km) and Lower Mantle. Asthenosphere is in a semi­molten plastic state, and it is thought that this enables the lithosphere to move about it. Within the asthenosphere, the velocity of seismic waves is considerably reduced (Called ‘Low Velocity

 The line of separation between the mantle and the crust is known as Mohoviricic Discontinuity.

 

The Core of Earth

Beyond a depth of 2900 km lies the core of the earth. The outer core is 2100 km thick and is in molten form due to excessive heat out there. Inner core is 1370 km thick and is in plastic form due to the combined factors of excessive heat and pressure. It is made up of iron and nickel (Nife) and is responsible for earth’s magnetism. This layer has the maximum specific gravity. The temperatures in the earth’s core lie between 2200°c and 2750°c. The line of separation between the mantle and the core is called Gutenberg­Wiechert Discontinuity.

 

Earth Movements – Endogenetic Movements

The interaction of matter and temperature generates these forces or movements inside the earth’s crust. The earth movements are mainly of two types: diastrophism and the sudden movements.

The energy emanating from within the earth is the main force behind endogenic geomorphic processes.

This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere.

Diastrophism

Diastrophism is the general term applied to slow bending, folding, warping and fracturing.

Wrap = make or become bent or twisted out of shape, typically from the action of heat or damp; make abnormal; distort.

All processes that move, elevate or build up portions of the earth’s crust come under diastrophism. They include:

orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth’s crust;

epeirogenic processes involving uplift or warping of large parts of the earth’s crust;

Earthquakes involving local relatively minor movements;

Plate tectonics involving horizontal movements of crustal plates.

In the process of orogeny, the crust is severely deformed into folds. Due to epeirogeny, there may be simple deformation. Orogeny is a mountain building process whereas epeirogeny is continental building process.

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

Epeirogenic or continent forming movements

In geology, Epeirogenic movement refers to upheavals or depressions of land exhibiting long wavelengths [undulations] and little folding.

The broad central parts of continents are called cartons, and are subject to epeirogeny.

The movement is caused by a set of forces acting along an Earth radius, such as those contributing to Isostacy and Faulting in the lithosphere

Epeirogenic or continent forming movements act along the radius of the earth; therefore, they are also called radial movements. Their direction may be towards (subsidence) or away (uplift) from the center. The results of such movements may be clearly defined in the relief.

Uplift

Raised beaches, elevated wave-cut terraces, sea caves and fossiliferous beds above sea level are evidences of uplift.

Raised beaches, some of them elevated as much as 15 m to 30 m above the present sea level, occur at several places along the Kathiawar, Nellore, and Thirunelveli coasts.

Several places which were on the sea some centuries ago are now a few miles inland. For example, Coringa near the mouth of the Godavari, Kaveripattinam in the Kaveri delta and Korkai on the coast of Thirunelveli, were all flourishing sea ports about 1,000 to 2,000 years ago.

Epeirogenic movement - uplift

Subsidence

Submerged forests and valleys as well as buildings are evidences of subsidence. In 1819, a part of the Rann of Kachchh was submerged as a result of an earthquake. Presence of peat and lignite beds below the sea level in Thirunelveli and the Sunderbans is an example of subsidence.

The Andamans and Nicobars have been isolated from the Arakan coast by submergence of the intervening land.

Epeirogenic movement - subsidence - arakan yomaEpeirogenic movement - subsidence - arakan yoma

On the east side of Bombay island, trees have been found embedded in mud about 4 m below low water mark. A similar submerged forest has also been noticed on the Thirunelveli coast in Tamil Nadu.

A large part of the Gulf of Mannar and Palk Strait is very shallow and has been submerged in geologically recent times. A part of the former town of Mahabalipuram near Chennai (Madras) is submerged in the sea.

Orgenic or the mountain-forming movements

Orogenic or the mountain-forming movements act tangentially to the earth surface, as in plate tectonics.

Tensions produces fissures (since this type of force acts away from a point in two directions) and compression produces folds (because this type of force acts towards a point from two or more directions). In the landforms so produced, the structurally identifiable units are difficult to recognise.

In general, diastrophic forces which have uplifted lands have predominated over forces which have lowered them.

Sudden Movements

These movements cause considerable deformation over a short span of time, and may be of two types.

Earthquake

It occurs when the surplus accumulated stress in rocks in the earth’s interior is relieved through the weak zones over the earth’s surface in form of kinetic energy of wave motion causing vibrations (at times devastating) on the earth’s surface. Such movements may result in uplift in coastal areas.

An earthquake in Chile (1822) caused a one-metre uplift in coastal areas.

An earthquake in New Zealand (1885) caused an uplift of upto 3 metres in some areas while some areas in Japan (1891) subsided by 6 metres after an earthquake.

Earthquakes may cause change in contours, change in river courses, ‘tsunamis’ (seismic waves created in sea by an earthquake, as they are called in Japan) which may cause shoreline changes, spectacular glacial surges (as in Alaska), landslides, soil creeps, mass wasting etc.

Volcanoes

Volcanism includes the movement of molten rock (magma) onto or toward the earth’s surface and also formation of many intrusive and extrusive volcanic forms.

A volcano is formed when the molten magma in the earth’s interior escapes through the crust by vents and fissures in the crust, accompanied by steam, gases (hydrogen sulphide, sulphur dioxide, hydrogen chloride, carbon dioxide) and pyroclastic material. Depending on chemical composition and viscosity of the lava, a volcano may take various forms.

Pyroclastic adjective of or denoting rock fragments or ash erupted by a volcano, especially as a hot, dense, destructive flow.

 

Continental Drift Theory – Tectonics

The continental drift theory is the theory that once all the continents were joined in a super-continent, which scientists call Pangaea. Over a vast period of time, the continents drifted apart to their current locations. Alfred Wegener first supported continental drift. Wegener’s explanation of continental drift in 1912 was that drifting occurred because of the earth’s rotation. Fossil records from separate continents, particularly on the outskirts of continents show the same species.

5. World Geography Part 1 UPSC Notes | EduRev

 

Sea Floor Spreading – Paleomagnetism

Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.

Theory of seafloor spreading was proposed by Harry Hess.

Pale magnetism is the study of the record of the Earth's magnetic field in rocks, sediment, or archaeological materials. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. Rocks when heated above curie point records the magnetic fields direction and preserve it for millions of years.

  • Plate Tectonics – Indian Plate Movement

Plates are composed of lithosphere, about 100 km thick, which "float" on the ductile asthenosphere.

While the continents do indeed appear to drift, they do so only because they are part of larger plates that float and move horizontally on the upper mantle asthenosphere. The plates behave as rigid bodies with some ability to flex, but deformation occurs mainly along the boundaries between plates.

The plate boundaries can be identified because they are zones along which earthquakes occur. Plate interiors have much fewer earthquakes.

There are three types of plate boundaries:

1. Divergent Plate boundaries, where plates move away from each other.

2. Convergent Plate Boundaries, where plates move toward each other.

3. Transform Plate Boundaries, where plates slide past one another.

Divergent Plate Boundaries

These are oceanic ridges where new oceanic lithosphere is created by upwelling mantle that melts, resulting in basaltic magmas which intrude and erupt at the oceanic ridge to create new oceanic lithosphere and crust. As new oceanic lithosphere is created, it is pushed aside in opposite directions. Thus, the age of the oceanic crust becomes progressively older in both directions away from the ridge.

Because oceanic lithosphere may get sub ducted, the age of the ocean basins is relatively young. The oldest oceanic crust occurs farthest away from a ridge. In the Atlantic Ocean, the oldest oceanic crust occurs next to the North American and African continents and is about 160 million years old (Jurassic). In the Pacific Ocean, the oldest crust is also Jurassic in age, and occurs off the coast of Japan. Because the oceanic ridges are areas of young crust, there is very little sediment accumulation on the ridges. Sediment thickness increases in both directions away of the ridge, and is thickest where the oceanic crust is the oldest. Knowing the age of the crust and the distance from the ridge, the relative velocity of the plates can be determined. Relative plate velocities vary both for individual plates and for different plates. Sea floor topography is controlled by the age of the oceanic lithosphere and the rate of spreading.

 If the spreading rate (relative velocity) is high, magma must be rising rapidly and the lithosphere is relatively hot beneath the ridge. Thus for fast spreading centers the ridge stands at higher elevations than for slow spreading centers. The rift valley at fast spreading centers is narrower than at slow spreading centers. As oceanic lithosphere moves away from the ridge, it cools and sinks deeper into the asthenosphere. Thus, the depth to the sea floor increases with increasing age away from the ridge.

Convergent Plate Boundaries

 When a plate of dense oceanic lithosphere moving in one direction collides with a plate moving in the opposite direction, one of the plates sub ducts beneath the other. Where this occurs an oceanic trench forms on the sea floor and the sinking plate becomes a sub duction zone. The Wadati-Benioff Zone, a zone of earthquakes located along the subduction zone, identifies a subduction zone. The earthquakes may extend down to depths of 700 km before the sub ducting plate heats up and loses its ability to deform in a brittle fashion.

As the oceanic plate subducts, it begins to heat up causing the release water of water into the overlying mantle asthenosphere. The water reduces the melting temperature and results in the production of magmas. These magmas rise to the surface and create a volcanic arc parallel to the trench. If the subduction occurs beneath oceanic lithosphere, an island arc is produced at the surface (such as the Japanese islands, the Aleutian Islands, the Philippine islands, other Caribbean islands

Transform Plate Boundaries

 Where lithospheric plates slide past one another in a horizontal manner, a transform fault is created. Earthquakes along such transform faults are shallow focus earthquakes.

 Most transform faults occur where oceanic ridges are offset on the sea floor. Such offset occurs because spreading takes place on the spherical surface of the Earth, and some parts of a plate must be moving at a higher relative velocity than other parts One of the largest such transform boundaries occurs along the boundary of the North American and Pacific plates and is known as the San Andreas Fault. Here the transform fault cuts through continental lithosphere

Triple Junctions occur at points where three plates meet.

Hot Spots

Areas where rising plumes of hot mantle reach the surface, usually at locations far removed from plate boundaries are called hot spots. Because plates move relative to the underlying mantle, hot spots beneath oceanic lithosphere produce a chain of volcanoes. A volcano is active while it is over the vicinity of the hot spot, but eventually plate motion results in the volcano moving away from the plume and the volcano becomes extinct and begins to erode.

Because the Pacific Plate is one of the faster moving plates, this type of volcanism produces linear chains of islands and seamounts, such as the

  • Hawaiian - Emperor chain, the Line
  • Islands, the Marshall-Ellice Islands,
  • and the Austral seamount chain Types of Mountains – Classification of Mountains

 

 

GEOGRAPHY OF THE WORLD

 

DEMOGRAPHY:

Continent

Density person/sq. km

Asia

108

Europe

101

South America

21

Africa

20

North America

14

Oceania

3

 

Urbanization by Continents:

 

Continent

Urbanization

South America

78

Europe

74

North America

68

 

 

Top 20 Countries by Area

 

Country

Area (lakh sq km)

S. N

Country

Area (lakh sq km)

Russia

170

11.

Algeria

23

Canada

99

12.

Dem. Rep of Congo

23

United States

96

13.

Mexico

19

China

95

14.

Saudi Arabia

19

Brazil

85

15.

Indonesia

19

Australia

76

16.

Libya

17

India

32

17.

Iran

16

Argentina

27

18.

Mongolia

15

Kazakhstan

27

19.

Peru

12

Sudan

25

20.

Chad

12

 

 

 

Contributions of Important Geographer

1.

Megalopolis concept

Jean Gottman

2.

Conurbation Concept, Wrote ‘Cities in Evolution’

Patrick Geddes

3.

Polar Front Theory

J. Bjerknes

4.

Anticyclone term

Sir Francis Galton

5.

Equilibrium Theory of tides

Issac Newton

6.

Dynamic Theory of Tides

Laplace

7.

Progressive Wave Theory

William Whewell

8.

Canal Theory

G. B. Airy

9.

Stationary Wave Theory of Tides

R. A. Harris

10.

Process of Precipitation

Bergeron

11.

First used the term Ecology

Tansley

12.

Father of Ecology

Haeckel

13.

First used the term plate

J. T Wilson

14.

Coined the term Antecedent Stream

J. W. Powell

15.

Classification of clouds

Luke Howard

16.

Ice crystal Theory

Tor Bergeron

17.

Collision-Coalesce Theory

George Simpson & Mason

18.

Glacial Control Theory of Coral reef formation

Daly

19.

Subsidence Theory of Coral reef formation

Darwin

20.

Stand Still Theory of Coral reef

Murray

21.

Concept of grade

G.K. Gilbert

22.

Law of Stream number/Length

R. E. Horton

23.

Location Allocation Models

P. Haggett

24.

Law of Retail Gravitation

W.J. Reilly

25.

Concept of Threshold & Range

B.J.L. Berry

26.

Introduced the concept of Possibilism

Lucien Febvre

27.

Coined “Areal Differentiation”

Hartshorne

28.

General System Theory

Ludwig von Bertalanffy

29.

Developed Hythergraph

G. Taylor

30.

Polyconic Projection

Ferdinand Hessler

31.

Globular projection

S.J. Fournier

 

 

 

Minerals & Their Largest Producers

1.

Graphite

Madagascar

2.

Gold

South Africa, Australia

3.

Platinum

South Africa, Canada.

4.

Chromium

South Africa, Russia

5.

Diamond

South Africa, Republic of Congo & Australia

6.

Zinc

Canada, Australia

7.

Uranium

Canada, USA, Australia, Niger, France, South Africa

8.

Nickel

Canada, Russia, Australia, USA.

9.

Coal

China, USA, India, Russia

10.

Steel

China

11.

Iron Ore

China, Brazil, Australia.

12.

Cement

China

 

13.

Manganese

China, South Africa, Australia.

14.

Paper

Canada

 

15.

Hydro Power

Canada, USA,

(Norway highest %age User)

16.

Tungsten

China, Thailand, Korea

 

17.

Asbestos

Canada Russia, Zambia, Zimbabwe

18.

Natural Gas

Russia, Canada, Algeria, Iran

19.

Flax

Russia

 

20.

Tantalum

Australia

 

21.

Bauxite

Australia, Guinea, Jamaica & Brazil.

22.

Lead

Australia, China, US

 

23.

Cadmium

Canada

 

24.

Antimony

China

 

25.

Uranium (Reser.)

Australia, Kazakhstan, Canada, South Africa

26.

Zirconium

Australia Brazil

 

27.

Titanium (Rutile)

*Australia*

 

28.

Iron

China, Brazil, Australia

29.

Copper

Chile, United States, Canada, Armenia, Zambia, Zaire

30.

Tin

China, Indonesia, Peru, Brazil, Malaysia

31.

Silver

Mexico, Peru, Chile & Poland.

32.

Mercury

Spain, China, Italy.

 

33.

Sulphur

Mexico, USA & Poland

34.

Rock Phosphate

USA, Peru (Guano).

 

 

 

Agricultural Commodities & Their Largest Producer

1.

Milk

India

2.

Coffee

Brazil, Vietnam

3.

Tobacco

China, turkey

4.

Pork

China

5.

Rice (export)

Thailand, Vietnam

6.

Rice

China, India

7.

Banana

India, Brazil

8.

Banana (Export)

Costa Rica, Jamaica, Honduras, Columbia

9.

Maize

USA, China

10.

Wheat

China

11.

Cork

Portugal

12.

Palm Oil

Malaysia

13.

Fresh Water Fish

Russia

14.

Barley

Germany, Canada, Russia, France

15.

Tea (Exporter)

Sri Lanka

16.

Rubber

Thailand, Indonesia, Malaysia

17.

Paper

USA

18.

Pulp (Export)

Canada

19.

Paper (Export)

Canada

20.

Sugar

India, Brazil, Cuba

21.

Sugar (Export)

Cuba

22.

Oil Palm

Malaysia, Indonesia

23.

Oil Palm (import)

India

24.

Cotton

China, USA, India, Pakistan, Uzbekistan in that order.

25.

Cotton (export)

USA

26.

Mangoes

India

27.

Manila Hemp (Abaca)

Philippines (75%)

28.

Raw Silk

China, Japan, India, Korea.

29.

Tobacco

China, USA, India

30.

Oranges

USA, Brazil

31.

Oats

Russia

32.

Millets

India

33.

Rye

Russia

34.

Sorghum

USA

35.

Pulses

India

36.

Sugarcane

Brazil

37.

Tea

India, China

38.

Dates

Iran, Egypt

39.

Olives

Spain

40.

Wine (Exporter)

*Algeria*

41.

Wine (Producer)

Italy, France

42.

Coconut

Indonesia, Philippines,

43.

Grapes

Italy, France

44.

Potato

China

45.

Soyabeens

U.S.A, Brazil

 

                                                                                                                                         

 

 

Sobriquets

 

1.

Island of Cloves

Zanzibar

2.

Land of Lilies

Canada

3.

Land of Golden Fleece

Australia

4.

Port of Five Seas

Moscow

5.

Island of Pearls

Bahrain

6.

Hermit Kingdom

Korea

7.

Land of Golden Pagoda

Yangoon (Myanmar)

8.

City of Canals

Venice

9.

Holy Land

Palestine

10.

Herring Pond

Atlantic

11.

City of Golden Gate

Sand Francisco

12.

City of dreaming Spires

Oxford

13.

Land of Canals

Netherlands

14.

Empire city

New York

15.

Land of Cakes

Scotland

16.

Land of Eskimos

Greenland

17.

Island of Pearls

Bahrain

18.

Granite City

Aberdeen, Scotland

19.

Garden of England

Kent

20.

Cockpit of Europe

Belgium

21.

City of brotherly Love

Philadelphia

22.

City of Magnificent Distances

Washington DC

23.

Gateway of tears

Bab-el-Mandab

24.

Textile Capital of Russia

Ivanovo

25.

Manchester of Japan

Osaka (Textile)

26.

Emerald City

Ireland

27.

The pearl of the Antilles

Cuba

 

Highest Peaks In Various Regions/ Mountain Chain

1.

Africa

Mt. Kilimanjaro

2.

North America

Mt. McKinley

3.

Europe

Mt. Elbrus

4.

Antarctica

Mt. Vinson

5.

Asia

Mt. Everest

6.

Oceania

Mt. Carstensz

7.

South America

Mt. Aconcagua

8.

Australia

Mt. Kosciusko

9.

Urals

Mt. Gora Naradnaya

10.

Alps

Mt. Mont Blanc

11.

Andes

Mt. Aconcagua

12.

Rockies

Mt. Elbert

13.

Appalachians

Mt. Mitchell

14.

South West Asia (Elbruz Chain)

Mt. Demavand

 

 

Important Places/Regions & Their Locations

1.

Llanos

Tropical Grasslands of Venezuela

2.

Campos

Tropical grasslands of Brazil

3.

Iberian Peninsula

Spain

4.

Katanga basin

Democratic republic of Congo

5.

Canterbury Plain

Largest lowland area of New Zealand

6.

Chaco / Gran Chaco

Low, flat, arid region covering Argentina Paraguay & Bolivia.

7.

Kra Peninsula

Malaysia

8.

Parana region

Brazil –Largest producer of wheat, corn cotton

9.

Matto grosso

Thick jungle in west central brazil north of Bolivia.

10.

Dogger bank

Shallow fishing area in north sea, 100km off UK

11.

Grand bank

Shallow fishing area off new foundland, Canada

12.

Georges bank

Near bay of fundy & Gulf of Maine

13.

Nordic Countries

Norway, Iceland, Greenland, Denmark.

14.

Ob, Yenisey & Lena

Major rivers of Russia

15.

Sarawak, Sabah, Labuan

These three states make up east Malaysia.

16.

Yucatan Peninsula

Mexico

17.

Ozark Plateau

heavily forested upland region, between the Missouri and

 

 

Arkansas rivers

18.

Sinai Peninsula

In north eastern Egypt.

 

 

 

Miscellaneous Data of Various Nations

 

S. No. 

Country/

Urban

Hydro

Nuclear

Thermal

Forest

 

Region

%

Elect %

%

%

%

1.

Canada

75

60

 

 

 

2.

USA

 

 

10

 

25

3.

Britain

 

 

24

 

 

4.

Italy

 

50

 

 

 

5.

Norway

 

90

 

 

 

6.

New Zealand

 

75

 

 

 

7.

Switzerland

 

74

 

 

 

8.

Japan

76

 

32

 

 

9.

France

 

 

77

 

 

10.

Lithuania

 

 

78

 

 

11.

Germany

 

 

30

 

 

12.

Australia

80

 

 

90

 

13.

S. E. Asia

20

 

 

 

 

14.

Russia

60

 

 

 

 

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