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Geologic Maps

A Practical Guide to the Preparation and Interpretation of Geologic Maps, Second Edition

Edgar W. Spencer

The ability to interpret geologic maps is a necessary skill for anyone interested in the surface and shallow subsurface of the earth. They show students of earth materials and structural geology how surficial materials and bedrock are distributed and configured in three dimensions. Those interested in natural hazards can use them to deduce fault locations. They reveal excavation problems and locations of natural resources to civil and environmental engineers and land-use planners. Historical geologists and geomorphologists gain valuable insight from the clues that maps provide about the natural processes that shape an area.

Geologic Maps serves all of those disciplines in addition to students in map interpretation and field geology courses. Spencer brings over 45 years of teaching experience to his step-by-step approach. He guides readers through the basics of map projections and content before discussing map interpretation using exercises taken from published geologic maps. He follows that with a presentation of geologic map preparation, giving map interpreters an appreciation of the level of precision represented by the data on geologic maps. Because of their widespread use in mapping, a short discussion of the use and interpretation of aerial photographs also is included.

$30.95 list, 148 pages

10-digit ISBN: 1-57766-462-0

13-digit ISBN: 978-1-57766-462-8

© 2000

Instructor's Manual available

“This text will supplement field experience in my field methods course. I really like the color geologic maps and always appreciate an inexpensive text for my students as they have many to buy each semester. I feel the text covers many important topics clearly and concisely, and is well written with well-thought-out illustrations.”  — Abigail Semple, Black Hills State University

Table of Contents

1. Maps and Images Used in the Study of Earth

Base Maps / Oblique Aerial Photographs / Vertical Aerial Photographs / Orthophotographs / Landsat Satellite Images / Side-Looking Airborne Radar (SLAR) Images / Geologic Maps / Geologic Cross-Sections / Geologic Block Diagrams / Structure Contour Maps / Tectonic Maps / Types of Information You Can Obtain from Maps and Images / Land-Use Maps Derived from Geologic Maps / Professional Uses of Geologic Maps

2. Base Maps

Map Projections / Topographic Maps

3. Preparation of Geologic Maps

Preliminary Preparations / Making a Reconnaissance Survey of the Area / Collecting and Recording Observations / Describing the Outcrop / Making Measurements with Compasses / Compiling Field Observations on the Base Map / Interpreting the Data / Field Checking Your Interpretation / Preparing the Final Map

4. Identification and Description of Sedimentary Rocks

Field Description of Sedimentary Rocks / Environments of Deposition / Primary Features in Sedimentary Rocks / Textural Variations in Sedimentary Rocks / Primary Features Found on Bedding Surfaces

5. Use of Aerial Photographs in Mapping

Vertical Photographs / Identifying Surficial and Bedrock Materials on Aerial Photographs

6. Interpretation of Surficial Geologic Maps

Uses of Surficial Geologic Maps / Types of Unconsolidated Materials Shown on Geologic Maps

7. Introduction to Geologic Maps of Bedrock

Primary Shape of Sedimentary Rock Bodies / Structure Contour Maps

8. Geologic Maps of Homoclinal Beds

Patterns of Homoclinal Beds on Geologic Maps / V-Shaped Contact Patterns on Geologic Maps / Determining the Strike and Dip of a Plane from Three Points of Known Elevation / Tracing Plane Contacts through the Topography / Layer Thickness and Width on Maps / Constructing Cross-Sections of Homoclinal Beds

9. Unconformities

Unconformity Patterns on Geologic Maps

10. Folds on Geologic Maps

Fold Geometry / Fold Patterns on Geologic Maps / Constructing Cross-Sections of Folded Rocks / Tracing Folds through the Topography / Structure Contour Maps of Folded Strata

11. Faults on Geologic Maps

Fault Nomenclature / Cross-Section Construction in Faulted Areas / High-Angle Faults / Patterns along Strike-Slip Faults / Low-Angle Faults

12. Igneous and Metamorphic Rocks

Appearance of Plutons on Geologic Maps / Nomenclature and Classification of Intrusions

Appendix I: Safety in the Field

Appendix II: Geologic Map Reference Set