Explanation:

duns

The longitudinal valley lying between lesser Himalaya and the shiwalik are known as Duns .Dehra Dun, Kotli Dun, Patli Dun are well known examples .`Dun ´ is a local word for valley. Dun lies between two intermittent ranges of the Himalayas as it formed as a result of folding when Eurasian plate and Indian plate collided. A pass is a navigable route through a mountain range .Most passes are flat at their summits and have the shape of a saddle