formation of himalayas

8/9/2019 Formation of Himalayas

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Adeeba Ifrah 12636


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Formation of Himalayas

225 million years ago India was a large island situated off the Australian

coast and separated from Asia by the Tethys Ocean. The supercontinent

Pangea began to break up 200 million years ago and India started a

northward drift towards Asia. 80 million years ago India was 6,400 km south

of the Asian continent but moving towards it at a rate of between 9 and 16

cm per year. At this time Tethys Ocean floor would have been sub ducting

northwards beneath Asia and the plate margin would have been a

Convergent oceanic-continental one just like the Andes today.

Between 40 and 20 million years ago the rate of northward drift slowed as the two continental plates collided and

the former Tethys Ocean closed. Neither continental plate could be sub ducted due to their low density/buoyancy.

This caused the continental crust to thicken due to folding and faulting by compressional forces. The continental

crust here is twice the average thickness at around 75 km. 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.


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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. The Himalayas and Tibetan plateau trend east-west

and extend for 2,900 km, reaching the maximum elevation of 8,848 meters (Mount Everest).


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The True Formation --- Chronology

Mountain formation mechanism

The mechanism of mountain formation was discovered long ago. When two continents clashes in the point of

contact rocks are exposed by enormous strength. These strengths crush rocks, gathers it in flexures, compress,

deform, and change its elemental composition. Some parts of rocks mount and turn into mountain peaks, others

press in the depth of the earth mantel and form “roots” of mountains. Mountain range like Himalayas present in

fact thickness of crust, consisting of rocks pushed out upwards and downwards.

Besides, abyssal mantel of the Earth consists of more solid rocks than the earth's crust above it. When the crustbecomes thicker it emerges in some way above mantel and mountain range becomes higher. However this

descent is balanced by weathering. Influence of weather conditions smooth’s little by little mountain peaks.

Mountain peaks

On this photo you can see Annapurna – one of the Himalayas peaks, which height exceeds 8 km above sea level.

Up to now these peaks rises to 10 cm in the century, but is weathered with the same speed. Fractions of rocks

are carried away in the sea by powerful rivers, such as Gang.


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25 million years ago

While India was moving towards Asia rocks collapsed into folds. One of them were pressing down, thus forming

roots of the mountains, others were going up in the form of mountain ranges. The crust that was lying between

two continents shortened on 2500 km and big platform ofcontinental crust with the width about 290 km has

probably crept in Asian platform thus raising Tibet.

Nowadays

High pressure changes chemical structure

of rocks at the bottom of mountain range. Carrying capacity pushes out mountain upwards, but their peaks are

ruined under the influence of wind and water. Subduction of India under Asia continues at speed of 5 cm a year.


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Roof of the world

On this photo from cosmos one can see

flood-lands of the river Gang (in the left),

peaks of Himalayas and Tibetan plateau, covered with snow (in

the right).

Future of the HimalayaOver periods of 5-10 million years, the plates will continue to move at the same rate, which allows us to forecast

fairly reliably how the Himalaya will develop. In 10 million years India will plow into Tibet a further 180km. This is

about the width of Nepal. Because Nepal's boundaries are marks on the Himalayan peaks and on the plains of

India whose convergence we are measuring, Nepal will technically cease to exist. But the mountain range we

know as the Himalaya will not go away.

This is because the Himalaya will probably look much the same in profile then as it does now. There will be tall

mountains in the north, smaller ones in the south, and the north/south width of the Himalaya will be the same.

What will happen is that the Himalaya will have advanced across the Indian plate and the Tibetan plateau will

have grown by accretion. One of the few clues about the rate of collision between India and Tibet before the GPS

measurements were made was the rate of advance of Himalayan sediments across the Ganges plain. There is an

orderly progression of sediments in front of the foothills. Larger boulders appear first, followed by pebbles, and

further south, sand-grains, silts, and finally very fine muds. This is what you see when you drive from the last hills

of the Himalaya southward 100 km. The present is obvious, but the historical record cannot be seen on the

surface because the sediments bury all former traces of earlier sediments. However, in drill holes in the Ganges

plain, the coarser rocks are always on the top and the finer pebbles and

muds are on the bottom, showing that the Himalaya are relentlessly

advancing on India.


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formation of himalayas

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