Geomagnetism

• Vine and mattheus • Molten lava get polarity

geomagnetic field of that period -Solidify

• Ocean floor – magnetic tape

Palaeo-magentism

conclusion1) Periodic reversal of magnetic field of the earth2) Rate of sea-floor spreading decided by age + distance between two equal magnetic stripes• Atlantic – 1.0 cm/ year• Indian – 1.5 cm/year• Pacific – 6.0 cm/year

Palaeo-magnetism

Continental drift Sea-floor spreading Plate tectonic theory

3 Theories

• Unanswered questions – • Formation of fold mountains?• Reason for earth quake?• Reason for volcanism on land?

Plate tectonic Theory

• Work of many scientists from different discipline

• Came out in 1960s• Based on 2 scientific evidences1) sea-floor spreading2) Palaeo-magnetismThe most latest and accepted theory

Plate tectonic theory

• Crust and upper part of mantle => lithosphere

• Asthenosphere = unique mechanical rigidity, semi-molten, plastic

• Lithosphere float over Asthenosphere

• Lithosphere is not continuous, broken, known as plates

Plates

• J.T Wilson termed –’Plate’ (litho, 100km)

• 3 types of plates:• Entirely oceanic,

entirely continental and both continental and oceanic

• 6 major and 20 minor plates

plates

Plates of the world

• Inner core= Fe, Ni• Outer core = Fe, Ni + silica• Mantle = Olivine• Oceans = basalt• Continents = granite and andesite

Chemical composition of Interior

Location of rocks

Example Property

Mantle Olivine highly fluid Heaviest

Oceanic crust

Basalt FluidHeavy

Continental crust

Andesite less mobileLighter

Continental crust

Granite least mobileLightest

geomorphFundam

entalRocks

Olivine

Basalt

Andesite

Granite

Burning and Melting of rocks

Divergent Boundary

Convergent Boundary

Transverse Boundary

Plate Interactions

• Ascending limb of convection current – below O /C

• Below ocean – MOR• Below continent – rift

valley, nascent sea

Divergent Plate Boundary

Oceanic crust - MORContinental crust

Divergent Plate Boundary

Rift valley

Nascen

t sea

Ocean

Phases of Divergent continental crust

Phases of Divergent continental crust

The Great African rift valley

Red sea – Nascent sea

Africa after 10 ml years

Knot of Plates

Knot of plates

Lakes and Nile river -African rift valley

African lakes

River Nile

• From 2011 on Blue Nile• Africa’s largest

hydroelectric dam• Egypt to lose water share

+ hydro electricity from Aswan

• Egypt showed reservation but Ethiopia did not pay heed

• Egypt ready for military intervention

• British treaties between Egypt and Sudan

Grand Renaissance dam, Ethiopia

• Nubian desert• Eastern desert• Namib desert• Lake Victoria• Lake Malawi• Lake Turkana• Lake chad• River Congo

• River Niger• Mt. Kilimanjaro • Katanga plateau• Grain coast• Ivory coast• Gold coast• Slave coast• Darfur

Locations in Africa

Prelims 2000

Q. Which one of the following lakes form an international boundary between Tanzania and Uganda?a) Chadb) Malawic) Victoriad) Zambezi

Ans.

UPSC

Question

O-O

•Island arc

O-C•Volcanic mountains

C-C•Fold mountains

Convergent Plate Boundary

O-O convergence

• Islands in S E Asia• Indo- Austral

plate and Eurasian plate movement

• Volcano + EQ

Island Arc

Mains 2014

Q. Explain the formation of thousands of islands in Indonesia and Philippines archipelago? (10)

UPSC

Question

Islands of South East Asia

Islands of Indian Ocean

O-O

•Island arc

O-C•Volcanic mountains

C-C•Fold mountains

Convergent Plate Boundary

O-C convergence

EX.• Andes ,

Rockies, Atlas mountain

• From Andes => andesitic rocks

• Volcano + EQ

Volcanic Mountains

Andes mountain range

• Atacama desert• Bolivian plateau• Lake Titicaca• Mt. Aconcagua (highest peak)• Mt. Cotopaxi• Mt. Chimbrazo• Lake Maracaibo

Location near Andes

Rockies mountain range

Grand canyon – Colorado river

• Columbia -snake plateau• Grand canyon /Colorado plateau• Death valley• Great salt lake• Mt.Logan (highest peak of rockies)• Mt. Mckinley (highest peak of N. America) in

Alaskan range

Locations near Rockies

Prelims 2005

Q. Where is the volcanic mountain. Mount. St. Helens is located?

a) Chileb) Japanc) Philippinesd) USAAns. D)

UPSC

Question

Mains2014

Q. why are the world’s fold mountain systems located along the margins of continents? Bring out the association between global distribution of fold -mountains and earthquakes and volcanoes (10)

UPSC

Question

O-O

•Island arc

O-C•Volcanic mountains

C-C•Fold mountains

Convergent Plate Boundary

C-C convergence

• Not located on coast

• No volcanism • But powerful EQ

• Ex. • Himalayas, Alps,

Urals

Continental Mountains

1. O-C convergence2. C-C convergence

Himalayan formation

Karakoram range

Alps mountain range

Physical map of Europe

Bosporus strait

City RiverParis SeineFrankfurt RhineVenice PoVienna, Budapest, Belgrade

Danube

Kiev DniesterBerlin Elbe

Cities of Europe

• Rivers: Rhone, Danube and Po• Black forest mountains• mountains: Pyrenees, Apennines• Islands of Mediterranean sea: Balearic,

Sardinia, Corsica, Sicily, Malta, Cyprus• Straits: Bonifacio, Messina, Marmara• Sea: Tyrrhenian, Adriatic, Ionian and Aegean

Locations near Alps

• When two plates slip pass-off each other

• No mountains but seismic activity

• San Andreas fault in California, USA

Transform Boundary

Plate movementSan Andreas fault, USA

San Andreas fault

• Early atmosphere – thin layer of H, He

• Numerous meteorites attack on earth

• Break the surface• Underlying lava

eruption• First oceanic crust

formed

Meteorite Impact theory

Continental drift Sea-floor spreading Plate tectonic theory

3 Theories

Prelims 2011

Q. Between India and East Asia, the navigation time and distance can be greatly reduced by which of the following?a) Deepening Malacca

strait between Indonesia and Malaysia

b) Opening a new canal across Kra Isthmus between gulf of Siam and Andaman sea

UPSC

Question

Mountains

Plateaus

Plains

Landforms on earth

mountains

Fold mountains

Block mountains

Types of mountains

Fold mountains

Mountains created due to convergent boundaries of both

1) O-C (Rockies, Andes) 2) C-C (Himalayas,

Alps)Compressive forces of platesYoungest mountains on earth

True mountains

Fold mountai

ns

Geomorph

1)Extensive mountain chain3) Great heights4) Formed along unstable parts of the earth5) Sedimentary deposits of marine origin (C-C)

Characteristics of Fold mountains

• Pull of descending limb of convection current

• great pressure of compressive force exerted by the convection cells

Phases of mountain building

• Elongated, narrow depression on continental margins

• Here sediments from both land and ocean accumulate

• Under intense pressure, sediments of geo-syncline folded

Geo-syncline

• Sediments from continental crusts of both plates + geo-syncline folded

• Because of sediments of geo-syncline – marine origin

C-C collision

Fold mountains of the world

1) Alaska range2) Rockies3) Andes4) Atlas mountains5) Pyrenees6) Caucasus 7) Taurus 8) Elburz and Zagros

9) Hindukush10) Kirthar range11) Kunlun Shan12) Urals mountains13) Appalachian mountains14) Great Dividing Range

List of mountains to locate

• understanding of the origin and evolution of earth’s crust.

• At the time of the formation of the earth crust, first basaltic crust of ocean - breaking and melting - a lighter continental crust developed.

• collide with one another = a larger land mass.• The joints = fold-mountains.

Importance of mountain building process

mountains

Fold mountains

Block mountains

Types of mountains

Block mountains formation

Block mountains formation

• Fault-block mt.• Due to forces within

interior of the earth• Uplifted part = horst• depressed part =

Grabben• Horst => block

mountains• Grabben => rift valley

Block mountains

EuropeIndia

Example of block mountains

Meaning:Table land, upland, higher than surrounding areas

• Raised land during mountains building process• Eroded

mountains• Eroded due to

glaciers• Deposition from

lava, wind

Plateaus

Intermontane plateau

• Bolivia plateau• Tibetan plateau• Columbia plateau• Colorado plateau• Anatolia Plateau

(Turkey)

• Deccan plateau• Katanga plateau• Ozark plateau

(USA)• Ethiopian

highland

Continental plateau

Types of plateau

Glacial plateau• Grahwal

plateau• Laurentian

plateau (Canada)

• Columbia-snake plateau (USA)• Deccan Plateau• Shan plateau

(Myanmar)

Lava plateauTypes of Plateau

• Origin of River Congo and Zambezi

• Dense equatorial forest• Known for resources- Gold, diamonds, Copper

Katanga Plateau

• Granite• Less mobile,

cannot move upward

• Backbone of fold mountains

Batholith

Plains

• Meaning• Flat areas with low

heights• Best for human

habitation• Most populated areas

of the world – alluvial plains of rivers

• Depositional plains- Rivers- Sea (sub-merged coast)

• Erosional plains- Erosion of plateau

Asia Europe

Africa

South America

North America

Indus Danube

Nile Amazon

Mississippi – Missouri

Ganga –Brahmaputra

Rhine Congo Parana- Paraguay

Colorado

Yangtze (China) Rhone Niger St. Lawrence

Hwang He (China)

Po Zambezi

Yukon

Ob- Irtysh (Russia)

Don Orange

Mackenzie

Mekong (SE Asia)

Euphrates - Tigris

Important river basins of the world

Yangtze river, China

• Navigable river – 35% of China’s population• Sichuan basin – rice cultivation• Shanghai – biggest port of China• Wuhan – Iron and steel• Nanjing – textile, iron and steel • Chengdu – oil and gas• Three gorge dam• Yun ho canal – connect Yangtze with Hwang He

Important locations

Euphrates- Tigris river, Iraq

• Lake Van, • Lake Urmia• Important centers in Iraq:• Baghdad, Mosul, Kirkuk, Al Basra

Locations near Euphrates-Tigris

Amazon river, Brazil

• Largest, 2nd longest river • Selvas – equatorial rain forest • Tin, rubber in Selvas • Sertao – ranching region• Petroleum reserve at the mouth• Manaus – Iron ore, navigable • plateau of Mato Grasso – gold reserve

Locations near Amazon river

Mississippi , USA

• Temperate grasslands – Prairies• Wheat, corn and cotton cultivation• Important cites: • Kansas – agriculture• St. Pittsburg – iron and steel• New Orleans – port, ship building

Locations near Mississippi basin

Murray-Darling basin, Australia

• Temperate grassland – downs• Wheat cultivation• Sheep rearing ,Animal husbandry• Wool and dairy production

Location near Murray-darling basin

Continental drift theory -> sea-floor spreading theory -> plate tectonic theory

Landforms on earthMountains (fold and block)

PlateausPlains