GEOLOGY CONTOUR MAPS CONTOUR MAPS This 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 Geology Contour ENRICHMENT4YOU Published by Henrich Incorporated Copyright 2005 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form by any means, electronic, mechanical, photocopying or otherwise, without first obtaining the written permission of the copyright owner.
GEOLOGY CONTOUR MAPS ABOUT THIS ENRICHMENT GUIDE This enrichment guide is designed to introduce you to contour maps. This Enrichment4You e-guide has two main sections: 1. Overview of Contour Maps - Pages 1-4. 2. Make a 3-D Contour Map - Pages 5-13. Geology Contour
GEOLOGY CONTOUR MAPS Maps have assisted people to navigate throughout history. A special type of map called a topographic map is designed to represent the various heights of the Earth s 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 those in land development for marketing purposes. C O N T O U R CORE CONCEPTS 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. Geology 1 Contour
GEOLOGY CONTOUR MAPS 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 area of 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. CORE CONCEPTS Geology 2 Contours 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.
GEOLOGY CONTOUR MAPS Scale Another important feature of contour maps is the scale. Scale indicates 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 map indicates 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. CORE CONCEPTS Geology 3 Contour Contour maps feature consistent contour levels. Contour levels and lines are shown through ratios. The first number in the ratio (the numerator) represents some consistent unit 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.
GEOLOGY CONTOUR MAPS 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 contour line will form a V that points upstream or up the valley or up the low area. Geology 4 Contour 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.