How do you read elevation, slope and stream direction from a topographic map's contour lines?
Read a topographic map: interpret contour lines and the contour interval, find elevation and relief, judge slope steepness from contour spacing, and use the rule of Vs to find stream direction (Virginia 2018 Earth Science SOL ES.1 and ES.6).
A SOL-level answer on topographic maps for the Virginia Earth Science EOC: what contour lines and the contour interval mean, how to find elevation and total relief, how contour spacing shows slope steepness, how the rule of Vs gives stream direction, and how to calculate gradient, with worked exam questions.
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What this topic is asking
Virginia Earth Science SOL standards ES.1 and ES.6 expect you to read a topographic map, one of the highest-value map skills on the EOC. Items give you a contour map and ask for an elevation, the contour interval, the steepest slope, the direction a stream flows, or a gradient calculation. The underlying idea is that contour lines turn a three-dimensional landscape into a two-dimensional picture of elevation.
Contour lines and the contour interval
To find the contour interval, take two labeled index contours, find the elevation difference, and divide by the number of spaces between them. Once you know the interval, you can label every line.
Reading slope from contour spacing
Special features: hills and depressions
A series of closed contour loops, with elevations increasing inward, shows a hill or mountain; the highest point is inside the innermost loop. A closed loop with hachure marks (short ticks pointing toward the center) shows a depression (a pit or crater), where the land goes down rather than up. Reading whether you are going up or down is essential before answering an elevation question.
Relief
Stream direction: the rule of Vs
When a contour line crosses a stream or valley, it bends into a V shape. The V points upstream, that is, uphill toward the higher land, because the stream has cut a valley into the slope. Therefore the stream flows in the opposite direction, toward the open end of the V (downhill). This "rule of Vs" lets you find which way a river flows from contours alone, a frequent EOC item.
Calculating gradient
The gradient measures how steep the land is between two points:
For example, if the elevation rises 250 m over 5 km, the gradient is m/km. A larger gradient means a steeper slope, which matches closer contour lines.
Try this
Q1. A topographic map shows widely spaced contour lines. What does this tell you about the slope? [1]
- Cue. The slope is gentle (nearly flat), because elevation changes slowly over distance.
Q2. Two points are 4 km apart at elevations of 100 m and 300 m. Calculate the gradient. [2]
- Cue. m/km.
Exam-style practice questions
Practice questions written in the style of VDOE exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
VA Earth Science SOL 2023 (style)1 marksOn a topographic map, what does it mean when the contour lines are very close together? (A) the land is flat. (B) the slope is steep. (C) the elevation is low. (D) there is a river.Show worked answer →
A 1-point multiple-choice item on contour spacing.
The correct answer is B. Closely spaced contour lines mean the elevation changes a lot over a short horizontal distance, so the slope is steep. Widely spaced contours (A) mean a gentle, nearly flat slope. Spacing shows steepness, not the absolute elevation (C), and a river (D) is shown by contours bending upstream in a V.
The test rewards the rule: close contours mean steep slopes, wide contours mean gentle slopes.
VA Earth Science SOL 2024 (style)2 marksTwo points on a topographic map are 5 km apart. One is at an elevation of 200 m and the other at 450 m. (a) Calculate the gradient between them. (b) State what the gradient tells you about the slope.Show worked answer →
A 2-point calculation item using gradient.
(a) 1 point: gradient is the change in elevation divided by the distance, m/km.
(b) 1 point: a gradient of 50 m/km means the land rises 50 meters for every kilometer of horizontal distance, a measure of how steep the slope is (a larger gradient means a steeper slope).
Markers reward the correct gradient with units in (a) and the interpretation that gradient measures slope steepness in (b).
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Sources & how we know this
- 2018 Science Standards of Learning (Earth Science) — Virginia Department of Education (2018)
- SOL Practice Items (All Subjects) — Virginia Department of Education (2024)