Interpreting a geological map

Asked by: Christina Cornwell

How is a geologic map interpreted?

The purposes of a geologic map are to show the surface distributions of rock units, the locations of the interfaces or contacts between adjacent rock units, the locations of faults, and the orientations of various planar and linear elements. (Standard geologic symbols are shown in Appendix F.)

What is the importance of interpreting a geologic map?

Geologic maps can also show how the physical environment has been impacted by human activity. Our understanding of issues important to society, such as natural hazards, climate change, economic development, sustainability, and management of soil and water resources is grounded in geologic maps.

What is geologic interpretation?

Definition: Compilation and synthesis of all the available geological information in order to get an as precise as possible model of the mineral resource.

What does a geological map describe and show?

A geologic map shows the distribution of materials at or near the Earth’s surface. Rock types or unconsolidated materials are generally grouped into map units and depicted using different colors. Geologic maps show information collected manually in the field by walking Vermont’s landscape.

What are the features of a geologic map?

Three main elements commonly found in a geological map are map units, contacts and faults, and strike and dip. Map units show different rock types and other earth materials, with the specific color and symbol.

What does the red line on the geological map indicate?

The colors of the lines usually indicate similar classes of information: topographic contours (brown); lakes, streams, irrigation ditches, and other hydrographic features (blue); land grids and important roads (red); and other roads and trails, railroads, boundaries, and other cultural features (black).

What are the uses the uses of geological maps?

Geological maps have found wide application in the measurement of rock bodies and interpretation of their structural features, and are of use to many soil, water, mineral, construction and petroleum research programs.

What are the elements of the map that will help you interpret the content?

Map Elements. Most maps contain the same common elements: main body, legend, title, scale and orientation indicators, inset map, and source notes.

What is the difference between topographic map and geological map?

Topographical maps show features seen from above the earth surface whereas geological maps give us information about beneath the earth surface.

What do the different colors and several character codes of a geologic map represent?

One of the first things you’ll probably notice about a geologic map is the many different colors. These colors represent the different geologic units, which are simply the type of rock formations of a certain age.

What do lines separating different rock units on a geologic map represent?

Only the bedrock surface would remain. Each area with a different color or pattern on a bedrock map represents a different rock type or a rock type of a different age (different “geologic units”). The line separating one type of rock from another or rocks of different ages is what geologists call a “contact.”

How do you read a map?

Quote from video: Now for every standard map that exists north will be at the top of the map as you can see this is standard map north is that the top south is at the bottom. There are however exceptions.

What is a unit on a geological map?

The “cartographic units” (geological map units) are the essential elements of a geological map. A cartographic unit is the representation of a volume of rock with a lithology or constant lithologic association, of a determinate age, limited by surfaces that make contact with the adjacent bodies of rock.

How many types of geological maps are there?

How to Read and Understand Geological Maps

How do you read a map?

Quote from video: Now for every standard map that exists north will be at the top of the map as you can see this is standard map north is that the top south is at the bottom. There are however exceptions.

What are the elements of the map that will help you interpret the content?

Map Elements. Most maps contain the same common elements: main body, legend, title, scale and orientation indicators, inset map, and source notes.

How can you tell what type of fault a geologic map is?

Faults are marked on geologic maps with bold lines. These lines are broader than the lines used to mark contacts between rock units.

How are geological ages noted on the legend of a geological map?

Geologic Age and Formation Symbols



The letter symbols signify the name and age of the rock units in an area. The first letter refers to the geologic age, as shown above. The other letters refer to the formation name or the rock type. The geologic map of Rhode Island is a good example of how the symbols are used.

How do you tell from a geologic map the age and type of rocks?

On a geologic map, rock units will be defined by a color and/or a pattern that will indicate whether the rock is sedimentary, metamorphic or igneous. Alphanumeric symbols are commonly used to distinguish the age and type of rock on top of the colors and patterns.

How do you identify a reverse fault on a map?

In a reverse fault, the block down dip of the fault line moves up (U) relative to the opposite block (Figure 4d). You should be able to distinguish the type of fault by sorting out the direction of motion (this is one of your major goals for this chapter).