Question

On a topographic map, increasing spacing between successive contour lines uphill represents a slope.

• A. concave
• B. convex
• C. uniform
• D. waning

Hint:

Compare contour spacing at the foot of the slope with spacing near the top; spacing that grows as you go uphill means the ground is steep low down and flattens near the summit.

Answer 1

The Correct Option is B

This question checks how well you can read a ground profile from contour spacing on a plan. Picture a vertical cross-section running from the foot of the slope to its top, using the contour crossings to mark equal elevation steps.

1. concave: A concave profile has contours widening out at the bottom and packing closer near the top, so the ground is gentle low down and steep higher up. That is the reverse of what the question describes, so this is wrong.
2. convex: If contours pack tightly together at the foot of the slope and spread apart as you climb, each equal rise in elevation covers more and more horizontal ground near the top. The gradient is steep at the base and flattens near the summit, which is the definition of a convex ground profile, like the rounded crown of a hill. This matches the question exactly.
3. uniform: A uniform slope keeps the same contour spacing all the way up, so the gradient never changes. The question explicitly says the spacing is increasing, so uniform cannot be right.
4. waning: This is not a term used to classify slope profiles from contour spacing in surveying or terrain analysis, so it can be ruled out on definition alone.

Since the contour spacing grows steadily as you move from the base to the summit, the ground surface is steep near the bottom and flattens near the top. That is the textbook description of a convex slope.

Let's summarize:

• Close contour spacing means a steep local gradient; wide spacing means a gentle one.
• Convex slope: steep at the base, gentle at the top, spacing increases going uphill.
• Concave slope: gentle at the base, steep at the top, spacing decreases going uphill, the opposite of this question.

So the correct answer is convex, option (B).