Which of the following statements regarding characteristics of contour lines is INCORRECT?
Contour lines of different elevations cannot intersect.
Understanding Contour Line Characteristics in Surveying
Contour lines are lines on a map that connect points of equal elevation. They are fundamental tools used in topography to represent the shape and relief of the land. Understanding their characteristics is crucial for interpreting topographic maps and visualizing the terrain.
Let's analyze each given statement regarding the characteristics of contour lines to identify the INCORRECT one.
Analyzing Statements on Contour Line Properties
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Statement 1: Contour lines of different elevations can unite to form one line only in the case of vertical cliff.
This statement describes a specific situation. A vertical cliff is a feature where the ground drops vertically. Along the face of a vertical cliff, many different elevations exist at essentially the same horizontal location. On a 2D map, contour lines representing these different elevations would merge together to form a single line. This statement accurately reflects this characteristic of contour lines when depicting a vertical cliff. Therefore, this statement is generally considered CORRECT.
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Statement 2: Contour lines of different elevations cannot cross each other.
This is a fundamental rule of contour lines. If contour lines of different elevations were to cross, it would imply that the point of intersection on the ground has two different elevations simultaneously, which is physically impossible for typical landforms. Contour lines represent a single elevation value. Therefore, this statement is CORRECT.
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Statement 3: Contour lines of different elevations cannot intersect.
This statement is very similar to Statement 2, as crossing is a form of intersecting. Standard topographic principles state that contour lines of different elevations cannot cross or intersect, except in the specific case of a vertical cliff where they unite or merge. If "intersect" is strictly interpreted as crossing over one another, then they cannot intersect. However, if "intersect" is interpreted more broadly to include meeting along a line (as happens in a vertical cliff where lines of *different* elevations merge), then they *can* intersect in that specific scenario. Given that Statement 1 explicitly mentions the vertical cliff where lines unite, and Statement 2 says they cannot cross, the intended INCORRECT statement is likely based on a subtle distinction or a specific interpretation where "intersect" is considered possible in the vertical cliff case (as they meet along a line), making the statement "cannot intersect" false. Therefore, this statement is considered INCORRECT in the context of the provided options, because contour lines of different elevations *can* be considered to 'intersect' (meet along a line) in the case of a vertical cliff.
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Statement 4: Contour lines close to one another indicate a steep slope.
The spacing between contour lines directly represents the steepness of the terrain. When contour lines are close together, it means that the elevation is changing rapidly over a short horizontal distance, indicating a steep slope. When they are far apart, the slope is gentle. This statement is a correct characteristic of contour lines.
Based on the analysis, Statement 3 is the one that is INCORRECT, considering the nuances potentially intended by the question regarding the vertical cliff scenario where lines of different elevations unite.
| Statement | Characteristic Described | Correctness | Explanation |
|---|---|---|---|
| 1 | Lines uniting at vertical cliff | Correct | Accurately describes contour behaviour on a vertical cliff. |
| 2 | Lines of different elevations cannot cross | Correct | Fundamental principle; crossing implies two elevations at one point. |
| 3 | Lines of different elevations cannot intersect | Incorrect | Potentially incorrect because lines might be considered to 'intersect' (meet along a line) in a vertical cliff scenario where they unite/merge. |
| 4 | Close lines indicate steep slope | Correct | Direct relationship between contour spacing and slope gradient. |
Revision Table: Key Contour Properties
| Property | Description |
|---|---|
| Connects Equal Elevation | Every point on a single contour line has the same elevation. |
| Closed Loops | Contour lines form closed loops, although they may extend beyond the map boundaries. |
| Never Cross (Typically) | Contour lines of different elevations do not cross each other on a map, as it would mean a point has multiple elevations. |
| Merge at Vertical Cliff | In the case of a vertical cliff, contour lines of different elevations unite or merge into a single line on the map. |
| Spacing and Slope | Close spacing indicates steep slope; wide spacing indicates gentle slope. |
| Concentric Circles (Hill/Depression) | Closed contour lines represent a hill (elevation increases inward) or a depression (elevation decreases inward, often marked with hachures). |
| V-shape at Stream | Contour lines form a 'V' shape when crossing a stream, with the 'V' pointing upstream (towards higher elevation). |
| Never Bifurcate | A contour line never splits or divides into two lines of the same elevation. |
Additional Information on Contour Mapping
Contour maps are essential tools for various applications, including engineering, urban planning, geological surveys, and hiking. They provide detailed information about the terrain's shape, allowing users to visualize hills, valleys, ridges, and slopes.
The vertical interval between successive contour lines is called the contour interval. This interval is constant for a given map and is usually indicated in the map's legend. A smaller contour interval provides more detailed elevation information but can make the map cluttered in areas of steep terrain. A larger contour interval simplifies the map but provides less detail.
Understanding contour characteristics helps in interpreting landforms:
- Closely spaced contours mean steep ground.
- Widely spaced contours mean gentle ground.
- Uniformly spaced contours mean uniform slope.
- Contours far apart indicate flat land.
- Closed contour lines indicate a hill or depression.
- Hachures (short lines pointing inward) on closed contours indicate a depression.
- Contours V-ing upstream indicate a valley or stream.
- Contours U-ing or V-ing downstream indicate a ridge.
Mastering the interpretation of these lines is fundamental to working with topographic data.
Important Questions from Contouring
Which of the following statements are CORRECT for contour map?
1) Parallel contour shows uniform slope.
2) Very closed contour shows steep slope.
3) Very closed contour shows flat area.
4) Two contours at different elevation cut at right angle.While drawing a cross-section of a contour map, the following values were noted from point A to point B on a strip of paper to draw the graph - 500 m, 400 m, 300 m, 200 m, 200 m, 300 m, 400 m, 500 m.
Which cross-section would be drawn by using the above values?
Identify the correct statements.
i. Contour lines form sharp V-shaped curves across valley line, with the convex side of the curve towards the higher ground.
ii. Contour lines form U-shaped curves across valley line, with the convex side of the curve towards the higher ground.
iii. Contour lines form U-shaped curves across ridge line, with the concave side of the curve towards the higher ground.
iv. Contour lines form sharp U-shaped curves across ridge line, with the convex side of the curve towards the higher ground.
In case of uniform slope, the contour lines:
Contour lines cross a watershed or ridge line at _____ .
