How can you tell from a map if a mountain is steep?

On maps, points of equal height are linked by lines. These are called contour lines. The closer the spacing of these lines the larger the height change over a given horizontal distance on the ground.

Therefore very closely spaced contour lines would indicate that a mountain was steep.

Vertical cliffs may also be marked directly on a map. Please see the related links for examples of how differing height and rock features are marked on British Ordnance Survey maps.