Contour lines

Definition

Contour lines are lines on a map that connect points of equal elevation, representing the three-dimensional shape of the terrain in a two-dimensional format. These lines help visualize the slope and relief of the land, showing where the ground rises and falls. The spacing of contour lines indicates the steepness of the terrain; closely spaced lines signify steep slopes, while widely spaced lines indicate gentle slopes.

5 Must Know Facts For Your Next Test

1. Contour lines can never cross each other; if they did, it would indicate an impossible situation where two different elevations exist at the same point.
2. When contour lines form closed loops, they represent hills or depressions; a loop with hachures (short lines on the inside) indicates a depression.
3. The interval between contour lines is known as the contour interval, which remains consistent throughout the map and is critical for understanding elevation changes.
4. Index contours are thicker lines that are usually labeled with their elevation, making it easier to read and understand the topography quickly.
5. Reading contour lines allows geologists to infer geological structures, such as folds and faults, by analyzing how these lines bend or break.

Review Questions

• How can you determine the steepness of a slope using contour lines on a topographic map?
  • The steepness of a slope can be determined by examining how closely spaced the contour lines are on a topographic map. If the contour lines are very close together, this indicates a steep slope, as elevation changes rapidly over a short horizontal distance. Conversely, if the contour lines are farther apart, this suggests a gentler slope where elevation changes more gradually.
• What information can be gained from analyzing closed contour loops on a map?
  • Closed contour loops provide critical information about the terrain's relief features. If the loop is drawn with contours that increase in elevation as you move inward, it represents a hill or mountain peak. In contrast, if the loop is surrounded by hachured lines pointing inward, it indicates a depression or sinkhole. Understanding these loops helps in visualizing landscape forms and geological features.
• Evaluate the importance of contour intervals in understanding geological maps and their implications for land use planning.
  • Contour intervals play a crucial role in understanding geological maps because they define the vertical spacing between contour lines, allowing for accurate interpretation of elevation changes. This understanding is essential for land use planning, as it affects water drainage patterns, construction site selection, and potential erosion areas. By evaluating the implications of contour intervals, planners can make informed decisions that take into account the natural landscape's characteristics and challenges.

Related terms

elevation: The height of a point above sea level, commonly used in mapping to understand topography.

topographic map:

A detailed representation of terrain features using contour lines to show elevation and landforms.

gradient: The rate of change of elevation over a certain distance, which can be inferred from the spacing of contour lines.