Which physical feature of India prevents the cold winds from central Asia from entering the Indian subcontinents?

Correct — A. The Himalayas form a continuous wall of about 2,400 km along India's northern edge, high enough to stop the cold, dry continental air of Central Asia from crossing into the subcontinent.

That is why winters in north India are milder than at places on the same latitude outside the barrier. The same wall works the other way in summer, forcing the south-west monsoon to rise, cool and shed its rain on the Indian side. Option (a) is the only feature on the list with the height to do either.

Why the others are wrong

• (b)
  Indian plains — The Northern Plains are flat alluvium laid down by the Indus, Ganga and Brahmaputra systems. They lie behind the mountains and obstruct nothing — they are what the Himalayas shelter.
• (c)
  Coastal area — The coastal plains run along the Arabian Sea and the Bay of Bengal, in the south of the country, far from the direction the Central Asian winds come from.
• (d)
  Indian desert — The Thar Desert is low, open, sandy country in the north-west. It has no relief worth the name, and it lies well south of the mountain frontier.

This is the standard 'significance of the Himalayas' question, and the answer rests on one property: height combined with continuity.

A climatic divide needs both. The range stands far above the level at which moving air must rise, and it runs unbroken from the Indus gorge in the west to the Brahmaputra gorge in the east, so cold Central Asian air has no gap to come through.

Everything students are asked about follows from that: milder north Indian winters, a monsoon forced to rain on the Indian side, and perennial rivers fed by snow and glacier melt.

Key facts

• The Himalayas run about 2,400 km from the Indus gorge in the west to the Brahmaputra gorge in the east.
• They block the cold winds of Central Asia, which is why north India is warmer in winter than places at the same latitude beyond the range.
• They act as a climatic divide by forcing the south-west monsoon to rise and release its rain over India.
• Himalayan rivers such as the Indus, Ganga and Brahmaputra are perennial because snow and glacier melt feed them alongside rain.

Common traps

• Reading the question as being about rainfall and choosing a feature associated with the monsoon rather than with the winter winds.
• Thinking the Northern Plains qualify because they lie in the north, when it is height and not latitude that stops the winds.

No directly related past PYQ was found.