Explanation:

Himalaya
Himalayas are the young fold mountains. This is the highest mountain range of the world. Himalayas act as natural barrier. The extreme cold, snow and rugged topography discourage the neighbors to enter India through Himalayas. They run from west-east direction from Indus to Brahmaputra along the northern boundary of India.
Aravallis

• It runs from North East to South West for 800 km between Delhi to Gujarat.
• It is one of the oldest folding mountain ranges of the World.
• It is highly denuded. Its highest peak is Guru Shikhar.
• The Great Boundary fault (GBF) separates Aravallis from Vindhyan mountains.

THINK!

• Folding mountains
• Block mountains

Note: Western Ghats and Eastern Ghats are examples of block mountains.