Terrain interpretation from contours: straight, parallel, and widely spaced contour lines indicate which type of surface?

Introduction / Context:
Contour patterns on topographic maps provide quick visual cues about landform shapes and slopes. Recognizing standard patterns helps planners and engineers infer gradients, drainage, and suitability for alignment or development without detailed calculations.

Given Data / Assumptions:

• Contours are straight, mutually parallel, and widely spaced.
• Contour interval is constant.
• No abrupt curvature or convergence is present.

Concept / Approach:

Widely spaced contours signify gentle slope; close spacing indicates steepness. Straight and parallel contours suggest slope direction and magnitude are uniform across the area, i.e., the surface approximates a plane inclined at a constant angle. Curved or converging contours would imply varying slope (convex/concave surfaces) or topographic features like valleys and ridges.

Step-by-Step Solution:

Verification / Alternative check:

Check with gradient formula: slope = contour interval / horizontal spacing; constant spacing across the map patch implies constant slope.

Why Other Options Are Wrong:

Steep surface would show close spacing; flat surface would have extremely wide spacing or no contours; curved surface would show curvature in contours or varying spacing.

Common Pitfalls:

Interpreting very wide spacing as completely flat (whereas some gentle slope exists); overlooking localized irregularities hidden at coarse scale.

Final Answer:

An inclined plane surface (uniform slope)