Himalayas

Indian Physical geography

Formation of Himalayas:

• 225 million years ago (Mya) India was a large island situated off the Australian coast in a vast ocean. It was separated from Asia by the Tethys Sea.

• 200 Mya ‐ India ‐northward drift towards Asia due to tectonic plate movement & super‐continent Pangea began to break up about

• 80 Mya India ‐6,400 km south of the Asian continent but moving at a rate of between 9 and 16 cm per year.

• At this time Tethys Sea floor would have been subducting northwards beneath Asia and the plate

margin would have been a Convergent oceaniccontinental one just like the Andes today.

• Most of the thick sediments on the Indian margin of the ocean were scraped off and accreted onto the Eurasian continent in what is known as an accretionary wedge. These scraped‐off sediments are what now form the Himalayan mountain range.

• From about 50‐40 Mya the rate of northward drift of the Indian continental plate slowed to around 4‐6 cm per year. This slowdown is interpreted to mark the beginning of the collision between the Eurasian and Indian continental plates, the closing of the former Tethys Sea, and the initiation of Himalayan uplift.

• The Eurasian plate was partly crumpled and buckled up above the Indian plate but due to their low density/high buoyancy neither continental plate could be subducted. This caused the continental crust to thicken due to folding and faulting by compressional forces pushing up the Himalaya and the Tibetan Plateau.

• The thickening of the continental crust marked the end of volcanic activity in the region as any magma moving upwards would solidify before it could reach the surface. It is important to note that the Himalayas do not comprise a single range but a series of at three ranges running more or less parallel to one another.

• They are supposed to have emerged in three different phases following one after the other. After the Great Himalayas were formed, the second phase took place about 25‐30 Mya when the Middle Himalayas were formed. The Shiwaliks were formed in the last phase of the Himalayan orogeny.

• The Himalayas are still rising by more than 1 cm per year as India continues to move northwards into Asia, which explains the occurrence of shallow focus earthquakes in the region today.

• However, the forces of weathering and erosion are lowering the Himalayas at about the same rate. This shows that Himalayas are still in the process of formation. That's why Himalayas are considered young and restless.



Himalayas

The Himalayas consisting of 2500 km series of parallel ranges along east‐west direction forms a great geographic entity known as Indian subcontinent. This great wall‐like structure on northern side of subcontinent acts as physical barrier, creates climatic & drainage divide & profound influence on its culture.

(Draw Himalaya Diagram)


Physical Barrier

• It separates Indian subcontinent from central & East Asian countries.

• It acts as natural frontier protecting India from foreign

invasions since ages

Climatic Divide

• The Himalayas are integral in shaping monsoonal type of climate for Indian subcontinent

• The towering mountain chain provides an invincible shield to protect the subcontinent from cold winds

• The Himalayas also trap the monsoon winds, forcing them to shed their moisture within the subcontinent.

Drainage Divide

• It acts as a watershed between rivers of north & south to Himalayas.

• The mighty rivers like Yangtse flows north of the Himalayan range whereas the Ganges, Indus & Sutlej flow south of the

Himalayas.

Cultural Divide

• enabled development of very different cultural settings in the Indian subcontinent

• It is abode to large number of indigenous tribes & nomadic group who preserved their cultures.

• The Himalayan Rivers & monsoonal climate has influenced

economy & distinct religious practices.