Transcript File - Geography World of Jaydeep Mehta

ENDOGENOUS PROCESSES AND
ASSOCIATED LANDFORMS
THE EVER CHANGING LANDSCAPE
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Earth’s surface is ever changing
Endogenous processess- interior of the earth
Mountains, plateaus and plains formed
Occurences of volcanoes and earthquakes
Processess- slow and sudden
Many areas rise or subside
NOTABLE CHANGES
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Breaking of Gondwanaland 120 mya
Indian peninsula started drifting towards north
Took present shape around 40 mya
Raising of Himalayas- present height during last
1 million years.
FORCES OF DIASTROPHISM
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Folding
Faulting
Uplift
Depression
– Act Very slowly
– Effects visible after thousands of years
• Two types of diastrophism
– Vertical forces
– Horizontal Forces
VERTICAL FORCES
• Continental rise and sink
– Upward forces- Uplift
– Downward forces- Subsidence
• Do not disturb the horizontality of rock layers
• At the most, layers may be inclined or tilted.
HORIZONTAL FORCES
• Mountain- building forces
• Act in a horizontal direction
• Disturb horizontal layers of rocks
– Compression- body pushed from opposite sides
– Tension- Rocks are pulled apart
FOLDING
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Bending of horizontal layers of rocks
Tilting or twisting of rock strata
Caused by compression
Formation of series of crests and troughs
Anticlines & synclines
– Anticlines- limbs incline in different directions
– Synclines- limbs incline in same direction
TYPES OF FOLDS
• Symmetrical folds- both limbs equally bent, inclined
at almost equal angles to the horizontal.
• Asymmetrical folds- one limb pushed too far, one
side gradual slop, other side steeper
• Monoclinal fold- one fold is vertical
• Isoclinal fold- both sides are inclined in the same
direction
• Recumbent fold- one limb is pushed over the other,
both limbs are parallel to each other
• Overthrust fold- fracture occurs, one limb slides
forward over the other limb.
FAULTING
• Result of tension
• Rock strata cannot withstand tension, breaks
• Displacement along the fault plane.
– Normal Fault- blocks move in opposite direction,
fault plane has steep slope
– Reverse Fault- produced by compression, hanging
wall slips up, gentle fault plane
– Thrust Fault- one block thrusts upon the other,
may result in formation of folds
LANDFORMS ASSOCIATED WITH
ENDOGENOUS PROCESSES
• First Order Landforms- continents and oceans
• Second Order Landforms- mountains, plateaus
and plains
• Third Order Landforms- hills, valleys, deltas etc
• Mountains- 26%
• Plateaus- 33%
• Plains- 41%
MOUNTAINS
• Uplifted part of the earth from the
surrounding area
• At least 900 m asl, broad base, very high,
steep slope and narrow peak.
• Less than 900 m, landforms are called hills
– Fold
– Block
– Volcanic
– Dissected
Fold Mountains
• Folding of sedimentary rock strata
• These were located in areas of narrow,
elongated seas or lake basins- geosynclines
• Either folded from both sides
• Or one edge may be stable, other side is
moving which may squeeze the sediment
– Old Fold mountains
– Young Fold Mountains
Block Mountain
• Formed due to creation of faults caused by
tension
• Block mountains and grabens
• Flat tops, steep sides, flat bottomed rift valleys
Volcanic Mountains
• Lava thrown out and deposited around the
crater forming a mountain
• Also known as mountains of accumulation
• Thinner lava ( Basic), shield volcano
• Thicker lava( Acidic), conical volcano
Dissected Mountains
• Eroded by dynamic agents
• Worn down from previously elevated regions
– Nilgiris
– Girnar
– Rajmahal Hills
Influence of mountains on humans
• Climate- climate barriers
• Vegetation- variety of forests, rich timber, pastures,
raw materials for agro-based industries
• Minerals- Coal, Iron ore, gold, silver, gems, oil
• Rivers- source in he mountains, perennial, form
fertile alluvial plains
• Hydro-electricity• Health and Tourist resorts
• Political boundaries- international boundaries,
controversial, lost much of their significance
• Defence- not completely effective, passes are used
• Agriculture- terraced cultivation- valleys
PLATEAUS
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Elevated area compared to surrounding areas
Large flat top, steep cliffs, also called table land
Layered with sandstones, shales and limestones
Rivers and streams cut deep valleys and
canyons in this region, changes it into a
dissected plateau
• Average height- 300 to 1000 m above sea level
Types of Plateaus
• Intermontane- partly or fully enclosed by
mountains– Tibet, Bolivia and Mexico
• Piedmont- foot of a mountain, plain or sea on
the other side
– Patagonian Plateau, Appalachian Plateau, Malwa
Plateau
• Continental- Surrounded by seas or plains,
formed due to continental uplift, quite vast
– Plateaus of Brazil, South Africa, South India,
Arabian Peninsula
Influence of Plateaus on humans
• 33% of earth’s surface, 9% of population
• Climate- Cooler climates in Torrid Zone, high
altitudes
• Agriculture- Deccan Plateau, volcanic soil
• Minerals- Chotanagpur plateau- coal and iron ore,
Australian Plateau- gold, silver, manganeese,
Brazilian Plateau- iron ore and manganese, Bolivian
Plateau- tin deposits
• Transport- not well developed
• Hydro-electricity- rapids on rivers
• Pastures- arid climates, grass grows well, Patagonia,
Turkey and South African Plateaus
PLAINS
• Relatively flat and low lying surface
• Some of them are rolling plains, some located
at very high altitudes.
– Mississippi plains- 30 m to 1500 m either side
– Ganga Plains- 6 to 8 m to 200 m above sea level
– Kashmir lake plain- 1700 m above sea level
Types of Plains
• Structural plains- coastal areas, upliftment of
continental shelf
• Erosional Plains- formed due to erosion of elevated
land- Peneplains, Karst Plains, plains of glacial
erosion, Desert plains
• Depositional Plains- Deposition of material in
lowlands, most plains in this category
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Alluvial- deposition by rivers- bhabhar, bhangar, khadar
Loess- deposition by wind
Coastal- deposition by sea waves
Lava plains- thin lava, spreads wide
Influence of Plains on humans
• Old civilizations, cradles of civilization
• Agriculture- easy to irrigate, 85% of worlds
agricultural produce comes from 41 % of world’s
plain areas
• Transport- Flat terrains, waterways also developed
apart from roads and railways
• Population- 90% world’s population live here, rapid
pace of urbanization and industrialization
• Industries- large scale growth, cheap labour, ready
markets, lack mineral resources
• Urbanization- favourable conditions for growth of
urban areas.