【Ascend】 , 【Mount】 , 【Climb】 and 【Scale】 mean to move upward to or toward a summit.

【Ascend】 is the most colorless of these terms, for it implies little more than progressive upward movement.

• 【ascend】 a mountain
• the car rapidly ascended the steep grade

It may be specifically used of movement along a river in the direction of its sourc.

• the Amazon can be ascended by seagoing ships 2300 miles

【Mount】 usually implies getting up on something above the level of the ground and is therefore preferred to 【ascend】 in some collocations; thus, one mounts or less commonly ascends a platform or a scaffold but one may 【ascend】 or 【mount】 a throne while one invariably mounts a horse.

【Climb】 usually suggests effort and ascent by the use of various means (as the hands and feet or gears or extra power).

• 【climb】 a tree
• 【climb】 the social ladder
• to 【climb】 steep hills requires slow pace at first
  —Shak.

【Scale】 adds to 【climb】 not only the suggestion of progression by steps but that of great difficulty; it is referable therefore to feats of climbing.

• 【scale】 a wall
• a ladder quaintly made of cords . . . would serve to 【scale】 another Hero’s tower
  —Shak.