Question

Why do landslides occur so frequently in the himalayas?

Answer 1

Himalayas mountains, mainly of sedimentary rocks formation, are more vulnerable than much older and stable block mountains of Western Ghats.

Landslides are the mass movement of soil / rocks / debris from a mountain slope during rainfall / river stream /earthquake.

The other factors which are strong with Himalayas for landslides occurrence than Western Ghats are -

Great height of Himalayas with steep slopes and numerous streams / rivers can carry high amount of debris resulting in landslides.
Compared to this WG were much eroded and denuded with steep slope on western side, whereas gentle slope on eastern side.
Small & swift flowing streams of western side and big matured rivers on eastern side (like Krishna, Godavari, etc) cannot carry large amount of debris.