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GEOLOGY CONTOUR MAPS

Geology

Contour

LEARN * DREAM * AWAKEN* DISCOVER * ENLIGHTEN * INVESTIGATE * QUESTION * EXPLORE

CONTOUR

MAPSThis Enrichment4You e-guide provides

a brief overview of contour maps

In this e-guide you will:

*Learn Basic Facts About Contour Maps

*Make a 3-D Contour Map

ENRICHMENT4YOU

Published by

Henrich Incorporated

Copyright 2005

All rights reserved. No part of this publication may be

reproduced, stored in a retrieval system or transmittedin any form by any means, electronic, mechanical, pho-

tocopying or otherwise, without first obtaining the writ-

ten permission of the copyright owner.

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ABOUT THIS

ENRICHMENT GUIDE

This enrichment guide is designed to introduce you to contour maps.

This Enrichm ent4You e-guide has two main sections:

1. Overv iew of Contou r Maps - Pages 1- 4.

2. Make a 3-D Contou r Map - Pages 5 - 13.


Geology

Contour


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CORECONCEPTSCO

N

T

O

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R


Geology

Contour

1


Contour maps can be very specific. Elevations of features can be

detailed down to the nearest foot or meter. These elevations are

indicated by spot elevations and benchmarks.

In the United States and certain countries, benchmark points have

been made. These benchmark points are brass plates references

that have been permanently positioned on the ground.

Benchmarks are shown on a topographical map by crosses and

the specific elevation for the location. The letters BM are

printed right in front of the cross and elevation.

Maps have assisted people to navigate throughout history. A

special type of map called a topographic map is designed to representthe various heights of the Earths surface (drawn to scale) but in a two

dimensional way.

Many people use topographic

maps including hikers, geologists,

historians and architects. In addition,

topographical maps are used in soil

conservation, emergency response

planning, crime solving, and by thosein land development for marketing

purposes.

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Geology

Contours

2

CORECONCEPTS

On topographical maps, relief is shown through the division of three main

groups:

1. Geographical features such as mountains, valleys, plains and hills.

2. Man made features such a roads, bridges, and buildings.

3. Water features such as streams, lakes, and ponds.

Contour intervals can represent both low and high relief areas.

Relief


Relief is the term used to

describe the difference in

elevation between any two

points on a land feature.

Simply, there are areas where there is

low relief such as valleys, deserts and around

lakes and high relief areas such as mountains

or steep gullies. A contour line shows an areaof the same elevation.

Relief also determines the contour

interval and contour line. A contour interval always represents the same elevation on

the same map, but may be different elevations on other maps.


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Geology

Contour

3

CORECONCEPTS

Scale

Contour maps feature consistent contour levels.

Contour levels and lines are shown through ratios.

The first number in the ratio (the numerator) represents some consistentunit of measure such as an inch, foot, meter etc.

The second number in the ration (the denominator) is usually much larger

and indicates the actual size of the feature on the earth.

The numerator can be different from map to map.

Another important feature of contour maps is the scale. Scaleindicates the relationship of the distance on a map and the actual

distance on the surface of the Earth. Scale is dependent on what

features will be presented, the size of paper being used and the

ability to accurately place the selected features on the map.

Generally, most features on maps are proportionately smaller than the actual feature.

Scale is most often shown as a fraction or ratio.

For example, 1:15,000 on a topographical mapindicates the following:

1 usually indicates the map distance

15,000 usually indicates the actual ground distance.

In this example, a 1:15,000 indicates that a unit (1

inch, 1 foot, etc.) equals 15,000 (inches, feet, etc.) on

the earth.



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Geology

Contour

4

Contour Basics

Regardless of the contour map, there are certain basics that apply

to all contour maps. These include the following:


1. Contours are spaced wide apart to indicate gentle slopes but spaced close

together on steep slopes.

2. Contour lines that are spaced evenly apart indicate that there is a uniformed

slope.

3. Contour lines to not cross over each other. The only exception to this is where

a cliff may overhang an elevation below.

4. A contour line always meets end to end.

5. A higher contour never occurs in between two lower contours and a lower

contour never occurs between two higher contours.

6. When a contour line crosses a stream, valley or other lower area, the contourline will form a V that points upstream or up the valley or up the low area.

7. When a gully, hollow or depressed area on the map needs to be shown, the

area is shown through closed hatch marks that are on the inside of the area being

featured.


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