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.
1 and 2
Analyzing Contour Map Properties
A contour map is a topographic map that illustrates the three-dimensional features of a land surface on a two-dimensional plane using contour lines. Each contour line connects points of equal elevation above a reference point, usually sea level. Understanding the spacing and pattern of these lines is crucial for interpreting the terrain's slope and shape.
Evaluating Statements on Contour Maps
Let's examine each statement about contour maps:
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Statement 1: Parallel contour shows uniform slope.
When contour lines are parallel and are spaced at equal distances from each other, it indicates that the rate of change in elevation is consistent across that area. This constant change in elevation over a horizontal distance means the slope is the same everywhere, defining a uniform slope. Therefore, this statement is correct.
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Statement 2: Very closed contour shows steep slope.
Contour lines that are very close together indicate a significant change in elevation over a short horizontal distance. A rapid change in elevation over a small area corresponds to a steep incline or decline. Thus, closely spaced contour lines represent a steep slope. This statement is correct.
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Statement 3: Very closed contour shows flat area.
A flat area has minimal change in elevation. On a contour map, flat areas are depicted by contour lines that are either very far apart or, in the case of a perfectly level area, absent altogether within that region (assuming the area is entirely between two contour intervals). Very closed contour lines, as discussed in Statement 2, signify a steep slope, not a flat area. Therefore, this statement is incorrect.
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Statement 4: Two contours at different elevation cut at right angle.
Contour lines represent specific, distinct elevations. A single point on the map can only have one elevation. If two contour lines representing different elevations were to intersect, it would mean that the point of intersection has two different elevations simultaneously, which is physically impossible. The only exceptions are vertical cliffs, where contour lines merge, or overhangs/caves, where contours might appear stacked or below others but don't strictly intersect in the plane of the map. They certainly do not cut at right angles. Therefore, this statement is incorrect.
Summary of Correct Statements
Based on the analysis:
- Statement 1 is correct: Parallel contours show uniform slope.
- Statement 2 is correct: Very closed contours show steep slope.
- Statement 3 is incorrect: Very closed contours show steep slope, not flat area.
- Statement 4 is incorrect: Contours at different elevations do not intersect.
Thus, the correct statements are 1 and 2.
Revision Table: Contour Map Properties
| Contour Line Pattern | Indicated Terrain Feature |
|---|---|
| Parallel and equally spaced contours | Uniform slope |
| Closely spaced contours | Steep slope |
| Widely spaced contours | Gentle slope or flat area |
| Concentric closed contours | Hill or depression (indicated by elevation values) |
| V-shaped contours (pointing uphill) | Valley or stream bed |
| U-shaped contours (pointing downhill) | Ridge or spur |
| Contours crossing a stream | Point upstream (V shape) |
| Contours at different elevations intersecting | Impossible (except vertical cliffs/overhangs where they merge/overlap) |
Additional Information: Understanding Contour Maps
Contour maps are essential tools in various fields, including geology, surveying, engineering, and hiking. They provide a visual representation of the topography of an area, making it easier to understand the lay of the land without being physically present.
- Contour Interval: The difference in elevation between successive contour lines is called the contour interval. This value is usually stated on the map legend. A smaller contour interval provides more detailed information about the terrain.
- Index Contours: Every fifth contour line is typically drawn bolder and labeled with its elevation. These are called index contours and help in quickly reading the elevation on the map.
- Reading Slope Direction: Water flows downhill, perpendicular to the contour lines. Valleys are indicated by V-shaped contours that point uphill (towards the origin of the stream). Ridges are indicated by U-shaped contours that point downhill.
- Highest and Lowest Points: The highest point within a set of closed contours representing a hill must be higher than the highest contour line, and the lowest point within closed contours representing a depression must be lower than the lowest contour line.
Interpreting contour lines effectively allows users to visualize the landscape, identify features like hills, valleys, ridges, and estimate the steepness of slopes, which is crucial for planning activities like construction, road building, or route planning for hiking.
Important Questions from Contouring
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 _____ .
The horizontal distance between two consecutive contours is termed as
