The Gulf of Maine has a variety of substrate, including exposed bedrock, gravel, sand, mud, clay, and silt. These bottom types are patchily distributed across water depths, resulting in an abundance of habitat types. Organizations such as the Gulf of Maine Mapping Initiative and individual scientists are mapping the seafloor more accurately than ever before. Because they were derived from few isolated points, previous maps underrepresented the heterogeneity of the floor of the Gulf of Maine. As new data are collected, they consistently indicate more complexity and variety in the benthos than previously appreciated. These more accurate substrate maps will help scientists, conservationists, and resource managers to better steward the Gulf of Maine and its biodiversity. Some of these efforts and the knowledge gained are described below.

Surficial Geology of the Seafloor

Surficial geology of the seafloor from US and Canadian data sources and discrete sample locations.

USGS Surficial Sediments
Data for each sample location and a full description of the complied sources are available through the USGS.
World Wildlife Fund – Canada and Conservation Law Foundation
US and Canadian data were combined into a 5 minute square grid and used in a seascape analysis.
Continental Margin Mapping (CONMAP) sediments grainsize distribution for the United States East Coast Continental Margin
Data are an overview of sediment size distributions and are available through the USGS Coastal and Marine Geology Program GIS Data Catalog
Scotian Shelf Regional Surficial Geology Compilation
Data are a compilation of previous works and extend to the Laurentian Channel; the full extent can be viewed online through Natural Resources Canada Geoscience Data Repository

Explore these datasets in an interactive PDF:


Mapping the seafloor is, quite obviously, a different challenge than mapping terrestrial geologic formations. A variety of technology has been developed that allows scientists to map the seafloor in impressive detail. The foremost of these is multibeam sonar, an acoustic system that can determine the ranges and reflectivity (indicating hardness) of objects underwater (for a complete description, please see Research Technology. Bathymetry, slope, terrain ruggedness, and sediment type can all be inferred from processed multibeam data.

For a map of multibeamed ares in the Gulf of Maine, visit the Gulf of Maine Mapping Initiative Coverage Map.

Further Exploration