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Using Geologic Maps
The distribution of materials at and below the land surface affects everyone who lives on this planet. In Maine, earth materials control everything from searching for ground water to siting a house foundation to protecting the environment to mining for precious gems. To make informed decisions, there needs to be a system which portrays the complicated pattern of rocks and earth materials which form the land surface. Geologic maps fill this need, portraying information such as the distribution of rock types and unconsolidated materials such as clay, sand, and gravel; landslide and erosion hazards; ground water availability; and much more. Browse the following pages to find out how to become a more informed reader of geologic maps.
Making Geologic Maps - the STATEMAP Program
The Maine Geological Survey (MGS) conducts geologic mapping throughout the state to provide landowners, planners, government agencies, educators, and industry with basic geologic resource information. Mapping projects are prioritized every year by the state’s Mapping Advisory Committee which are then funded through the U.S. Geological Survey National Cooperative Geologic Mapping Program’s competitive STATEMAP grant program and matching state funds. Geologists head out into the field spring through fall to observe and interpret geologic features in the selected areas. Work is completed by MGS staff geologists as well as contractors that are usually college professors and their students, so these mapping projects are also a way to mentor and educate new geologists. Mappers work from public roadways but also rely on the cooperation of towns and private landowners to access bedrock (ledge) and sediment exposures (such as gravel pits) to ensure accurate geologic interpretations and useful maps. Over the winter, observations and interpretations are compiled to create maps at the 1:24,000 scale (also referred to as detailed scale), which are usually finalized and published within the next year and available for free from MGS. MGS produces separate bedrock and surficial geology map series – details about these maps are their uses can be found in links below. Lastly, information collected during mapping projects is often used to create geologic guides for publicly accessible areas as part of the very popular Geologic Facts and Localities series.
Reading and Understanding Geologic Maps
Reading Maps with a Critical Eye: Becoming an Informed Map Reader
Use the links in the following list to learn more about the geologic maps produced by the Maine Geological Survey. The Description link will provide a description of the map series, and links to the map explanation and sidebar. The How to Read link will provide tips on how to read the geologic map.
Bedrock Geology | ||||
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Map series | Description | How to read | ||
Bedrock | View | View | ||
Coastal Marine Geology | ||||
Map series | Description | How to read | ||
Bluffs | View | View | ||
Marine Geologic Environments | View | |||
Coastal Sand Dune Maps | View | View | ||
Inner Continental Shelf | View | |||
Economic Geology | ||||
Map series | Description | How to read | ||
Peat Resource Evaluation | View | |||
Geologic Hazards | ||||
Map series | Description | How to read | ||
Landslide Hazards | View | View | ||
Landslide Susceptibility | View | |||
Surficial Geology | ||||
Map series | Description | How to read | ||
Surficial - detailed | View | View | ||
Surficial - reconnaissance | View | |||
Surficial - 1:250,000 | View | |||
Surficial Materials | View | View | ||
Water Resources | ||||
Map series | Description | How to read | ||
Sand and Gravel Aquifers | View | View | ||
Bedrock Ground-Water | View | |||
National Wetlands Inventory | View |
Last updated on May 1, 2020