Key words - Geo - PT-3

Major Landforms of the Earth

​Internal forces/tectonic forces/endogenetic forces > sudden changes > plates float over magma > magma rises heated, spreads, cools and then sinks again, to heat and then rises once more > this pushes the plate > thus plates constantly move > plate tectonics > plates converge > plates diverge > plates move in a transverse movement > all responsible or changes on earth > takes millions of years > can happen suddenly > by earthquakes, volcanoes and landslides

​Internal forces

​External forces

​exogenetic/ denudational/ gradational forces > slow and steady > agents of gradation > glaciers, wind, water > wearing away > rebuilding > eroding > transporting eroded materials > depositing weathered soil > to other places > rain, wind, rivers > erode highlands > deposit > forming plains

​Mountains

​Natural elevation > narrow summits > broad bases

​Fold Mountains

​uplifement and folding > due to lateral compression > tectonic forces > plates converge > the point compresses > gets crumpled/folded > Massive layers > uplifted

​Block Mountains

​plates diverge > faults > 2 faults > large area get vertically displaced > horst-block mountain > graben-rift valley

​Volcanic mountains

​conical/dome-shaped structure > vent > lava > flows over surface > hardens > several layers > volcanoes

​Importance of mountains

​- Climate > force clouds > carrying moisture > rise > condense > rain

​- Perennial rivers - Indus, Ganga, Brahmaputra

​- Reservoirs - freshwater lakes and springs

​- flora and fauna - lac, timber, fuel, nuts, fruits, medecinal herbs

​- Dams > irrigation > hydro-electricity > Bhakra-Nangal on Sutlej

​- Encourage tourism > Sporting activities

​Plateau

​Broad, level, elevated land > sharply falling sides > tableland > steep side > escarpment > Intermontane > completely/partially surrounded by mountains > Continental > rise abruptly from coasts/surrounding plains > lava > lava flows form fissures > spreads thickly over extensive areas

​Importance of Plateaus

​- Lava > Black soil > Cotton

​- deposits > Chhota Nagpur > iron ore, coal, manganese > African Plateau > gold, Diamond

​- Rivers > fall from escarpment > waterfall > turbines > electricity > Hundru on Subarnekha > Jog on Sharavati > Deccan Plateau

​Plains

​low-lying, vast flat land > 200m above sea > levelled alluvial tracts > deposits by rivers/tributaries > eroded materials > debris/alluvium > sand, silt, clay, animal, plant matter > rich nutrients > soil > cultivation

Importance of Plains

​- Water

​- cultivation

​- network of railways, roads

​- ports, harbours > international trade

​Examples

​Fold Mountains - Young - Himayalas and The Alps

Old - Aravalli (Rajasthan), Urals (Russia), Appalachians (N.A)

​Block Mountains - Vosges Mountains (Europe), Rhine Valley - Rift Valley

​Volcanic Mountains - Mauna Loa (Hawaii), Mt Kilimanjaro (Africa), Mt Vesuvius (Italy), Mt Fuji (Japan)

​Largest and Hightest Plateau - Chang of Tibet (4000-6000m)

​Roof of the world (Pamir Plateau), One of the oldest ( Deccan Plateau)

​East Africa, Tanzania, Kenya and Uganda

​Western Australia (300-400m)

​Nile Basin - Egypt, Hwang Ho Basin - China, Indo-Gangetic - India (Plains)

​Continued...