Landforms PPT
•CLASS
9
Landforms
of the Earth
•GEOMORPHOLOGY
•Geo
– earth, morph – form, ology – science
•Systematic
study of the earth’s relief feature
•Orogeny – mountain building
movements (9)
•Orogeny – extends in time
for some tens of millions of years
•Oro
– mountain , geny – formation
MOUNTAINS
•Mountain building period – between 600 and 3500
million years ago
•Three
recent orogenics are:
•Caledonian – 350 million years
old (examples: Mountains of Scotland and Scandinavia)
•Hercynian – 250 million years
ago (examples: Urals , Appalachians)
•Alpine
– 30 million years ago (examples: Himalayas, Andes, Rockies)
DEFINITION
OF MOUNTAINS
•Landform
that rise above the surrounding land
above 600 metres
•Landform
below 600m – hill.
•Peak-
highest part of the mountain.
•Ranges-
long chains of group of mountains.
•Mountain
System- a group of ranges, displaying
similar alignment, form, structure, originating from same general cause
TYPES
OF MOUNTAINS
•Fold
mountains or mountains of elevation or upliftment
•Block
mountains
•Residual
mountains or mountains of erosion
•Volcanic
Mountains
FOLD
MOUNTAINS
•Fold
Mountains- horizontal movements causing the Earth’s crust to wrinkle or fold.
•Anticline-
upfolds, Syncline- downfolds.
•Fold
mountains- are of two types:
–Young
Fold Mountains.
–Old
Fold Mountains.
PARTS
OF FOLD MOUNTAINS
FOLD
MOUNTAINS.
•Old
Fold Mountains:
–Formed
more than 250 million years ago.
–Have
low altitude, gentle slopes as they are subjected to denudation for millions of
years.
–Example:
Aravalli Range.
•Young
Fold Mountains:
•Formed
about 25 million years ago.
•Have
rugged relief features as they have been subjected to denudation for
comparatively short period of time.
•Example:
Himalayas, Andes, Rockies.s
FEATURES
OF YOUNG FOLD MOUNTAINS
•Series
of parallel ranges.
•Intermontane Plateau-
plateaus surrounded by mountains. Eg: Plateau of Tibet.
•Areas
of crustal instability.
•Waterfalls.
•Attract
tourists.
BLOCK
MOUNTAINS OR HORSTS
•Block
mountains- when tectonic plates move
away causing the surface of the Earth to crack apart.
•These
cracks cause faulting and result in a mass of land being pushed up between
parallel cracks to form a block. Example: Black Forest and the Vosges of the
Rhineland.
BLOCK
MOUNTAINS.
•Tensional
forces may cause the central portion to be let down between two adjacent fault
blocks forming a Graben or Rift Valley.
•Example:
The East African Rift Valley, The Narmada Valley between the Vindhya and Satpura ranges.
VOLCANIC
MOUNTAINS.
RESIDUAL
MOUNTAINS.
•These
are victims of erosion and the agents of gradation such as winds, rain, frost
and running water.
•Example:
Aravalli Ranges.
ROLE
OF MOUNTAINS.
•Effective
climatic barriers. Eg: Himalayas.
•Generates
hydroelectricity.
•Barriers
for communication.
•Causes
rainfall.
DISTRIBUTION
OF YOUNG FOLD MOUNTAINS.
•Circum-Pacific
Mountain Belt.
•Mid-World
Mountain Belt.
TYPES
OF PLATEAUS
•Are
elevated uplands, extensive in size and descending steeply to the surrounding
regions.
•Diastrophic
Plateau- large –scale deformation of the Earth’s crust.
•Plateaus
are classified according to their origin:
– Intermontane Plateau.
–Volcanic
Plateau.
TYPES
OF PLATEAU
Intermontane Plateau: enclosed by
fold mountains, e.g; Plateau of Tibet.
VOLCANIC
PLATEAU
•Formed
when successive layers of lava flowed out as a result of volcanic eruptions. e.g; Deccan Plateau.
PLAINS.
•Comparatively
level surface of land at a low elevation from sea, less than 150m above sea-
level.
•They
are caused by internal forces of Earth or by denudation or deposition.
•Types
of Plains:
–
Structural Plains- extensive lowlands bordering all continents, e.g: Belgium,
Netherlands etc.
–Depositional
Plains- formed by the depositional work of different agents of erosion like rivers, winds, glacier
etc.
DEPOSITIONAL
PLAINS
•Lacustrine Plains: formed by
filling lake beds by the silt brought down by rivers, e.g; The Great Lakes.
•Alluvial
Plains: formed by the sediments brought down by the rivers, e.g; The Ganga Plains.
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