Topographic Maps & Gradients — Practice · Grade 9 Science

Chapter: Investigating Earth

What this practice covers

By the end of Topographic Maps & Gradients you should be able to:

8 questions, numeric, multiple choice and written answer, each with a worked explanation.

Vocabulary used: contour, contour interval, gradient.

Problem 1

Elevation rises 60 m over a horizontal distance of 3 km. Find gradient.
Answer and explanation

20 m/km

60 ÷ 3 = 20.

Problem 2

On the same map, closely spaced contours indicate…
  1. gentler slope
  2. steeper slope
  3. lower rainfall
  4. higher temperature
Answer and explanation

steeper slope

The same elevation change occurs over a shorter horizontal distance.

Problem 3

Why is a map legend necessary?
Answer and explanation

It defines symbols and units; unfamiliar markings may change interpretation, such as a hill versus a depression.

Problem 4

Elevation rises from 120 m to 300 m over a horizontal distance of 3 km. Find gradient. Explain the reasoning in your own words.
Answer and explanation

60 meters of elevation change per kilometer horizontally.

Elevation change=300−120=180 m.

Gradient=180 m/3 km=60 m/km.

Response criteria

  • Use the stated conditions.
  • Show the evidence or calculation.
  • Explain the conclusion and any stated limitation.

Problem 5

Elevation rises 60 m over 300 m horizontally. Find gradient. Show the reasoning, not just the conclusion.
Hints

Use horizontal ground distance and actual elevations, not contour-line count alone.

Answer and explanation

60/300=0.20 m/m, or 20%.

Problem 6

Two maps have different contour intervals. Can line spacing alone rank their slopes?
Hints

State what the supplied observations or conditions establish, and separate that from any assumption.

Answer and explanation

No. Convert each map's elevation change and horizontal scale first; spacing is comparable only with compatible scales.

Problem 7

Closed contours can enclose either a hill or a depressionClosed contours can enclose either a hill or a depressionHillDepression150 m170 m150 m130 mHeights rise inward.Hachures and labels show inward fall.Closed contours alone are insufficient; inspect symbols and elevations.
These paired original maps isolate the difference between hills and depressions at the same 20 m interval. Hachure direction and labeled elevation together support the interpretation. The diagrams omit streams; the valley-V convention is explained in the adjoining prose rather than inferred from these circular contours.
Interpret the supplied visual model. Which central region is lower than its surrounding outer contour, and what two clues support that answer?
Answer and explanation

The right panel: its inner contour is 130 m compared with 150 m outside, and its hachures point inward toward lower ground.

The nested shape is similar in both panels. The tick marks and different height sequence change the interpretation.

The right panel: its inner contour is 130 m compared with 150 m outside, and its hachures point inward toward lower ground.

Response criteria

  • Read the labeled quantities, reference frame or objects correctly.
  • Explain the relation between the visual evidence and the mechanism.
  • Keep the drawing’s stated assumptions and limits in the conclusion.

Problem 8

A map scale is 1 cm = 0.4 km. Two points 3 cm apart along a stated map line rise from 220 to 280 m. Calculate average gradient and explain why it does not establish every local slope.
Answer and explanation

Ground distance is 1.2 km and rise is 60 m, so average gradient is 50 m/km. Local segments can be steeper or flatter; additional contour crossings or survey points are needed.

Convert 3×0.4 = 1.2 km.

Subtract 280−220 = 60 m.

Divide 60/1.2 = 50 m/km and distinguish the average from local values.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

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