Interactive US Geology Map: USGS State Geologic Map Compilation
This interactive US geology map draws on the State Geologic Map Compilation (SGMC), a seamless national database assembled by the U.S. Geological Survey from 48 individual state geologic maps. Use it to explore rock types, geologic unit names, and ages anywhere across the contiguous United States — from the sedimentary basins of the Great Plains to the plutonic cores of the Rocky Mountains and the ancient metamorphic terranes of the Appalachians.
Interactive US Geology Map
Select a state to filter the map and zoom to that region. Click any polygon to see the geologic unit name, age range, rock type classification, and the source state survey reference.
How to Use This Map
Getting Started
The map opens centred on the contiguous US at a regional zoom level. Because the SGMC contains millions of polygon features, the map loads geology for the current viewport — zoom in to load more detail in any area. A loading spinner appears whenever data is being fetched.
Filters and Controls
Use the State dropdown to filter the map to a single state. Selecting a state automatically zooms the map to that state’s extent and reloads only its geology. Choose All States to return to the national view. Click any coloured polygon to open a popup showing:
- Unit name — the full geologic unit description from the state survey
- SGMC and original labels — standardised and source map unit codes
- Age range — minimum and maximum geologic age (e.g. Cretaceous, Precambrian)
- Major rock type — the primary lithology classification (MAJOR1 field)
- Source reference — the state geologic map citation
Colour Legend
Polygons are coloured by broad rock category derived from the MAJOR1 field:
- Sedimentary — sandstone, limestone, shale, carbonate, and related rocks
- Metamorphic — gneiss, schist, quartzite, marble, and all metaXxx units
- Plutonic — granite, diorite, gabbro, syenite, and other intrusive igneous rocks
- Volcanic — basalt, rhyolite, andesite, dacite, and other extrusive igneous rocks
- Ultramafic — peridotite, dunite, serpentinite, and related mantle-derived rocks
- Unconsolidated — sand, gravel, clay, silt, and surficial deposits
- Mixed — migmatite and other composite units
Sharing a View
The URL updates automatically as you pan, zoom, and filter by state. Copy the address bar at any time to share a direct link to your current view.
About the SGMC Dataset
The State Geologic Map Compilation (SGMC) is a USGS national-scale geologic map database that merges 48 individual state geologic surveys into a single seamless dataset. It is the definitive spatial reference for bedrock and surficial geology across the contiguous United States, supporting research in mineral resources, groundwater, natural hazards, and land-use planning.
The SGMC standardises rock-type terminology and unit labels across state boundaries, making it possible to trace geologic formations across state lines — something that individual state maps, each produced with their own legend and classification scheme, could not easily support on their own. The dataset was compiled as part of the USGS National Geologic Map Database programme.
Data Sources and Limitations
Data is served live from the USGS ESRI feature service hosted on ArcGIS Online (service ID: 4d9fb5c0a6344407aec56f47a11482b5). The dataset reflects the August 2017 release of the SGMC geodatabase and has not been modified from the original USGS source.
Because the dataset contains millions of polygon features, the map displays a maximum of 1,000 features per viewport query. At small zoom levels (national or multi-state view) you will see a representative sample; zoom in to a county or sub-county scale to see full polygon coverage for any area. Filtering by state reduces the query scope significantly and improves completeness at regional zoom levels.
Rock-type colour categories shown on this map are derived from the MAJOR1 field using a classification applied by MapScaping. The SGMC MAJOR1 field contains over 250 distinct lithology terms; these have been grouped into eight broad categories (Sedimentary, Metamorphic, Plutonic, Volcanic, Ultramafic, Unconsolidated, Mixed, Unknown) for display purposes. The original MAJOR1 value for each unit is always shown in the popup.
Frequently Asked Questions
What does the SGMC stand for?
SGMC stands for State Geologic Map Compilation. It is a USGS database that combines individual state-level geologic maps into a single, nationally consistent dataset covering the 48 contiguous US states.
Why do some areas show only a few polygons at national zoom?
The map queries the USGS feature service live and returns up to 1,000 features per request for the visible area. At very small zoom scales (showing the whole country), this limit means only a sample of features is visible. Zoom in or filter by state to see complete coverage for a specific region.
What do the rock type colours represent?
Colours represent the broad rock category inferred from the MAJOR1 field in the SGMC: yellow for sedimentary rocks, blue for metamorphic rocks, orange/salmon for plutonic (intrusive igneous) rocks, red for volcanic (extrusive igneous) rocks, green for ultramafic rocks, and beige for unconsolidated sediments. Click any polygon to see the exact MAJOR1 value for that unit.
How current is the geology data?
The SGMC geodatabase used here reflects the August 2017 USGS release. Individual state source maps range in age; some reflect surveys conducted over many decades. For the most current state-level mapping, consult the relevant state geological survey directly.
Can I download the SGMC data?
Yes. The full SGMC geodatabase is available for download from the USGS: SGMC download on ScienceBase. The ESRI feature service used by this map is also publicly accessible at the URL provided on the ArcGIS Online item page.
Who produced this data?
The SGMC was produced by the U.S. Geological Survey (USGS). The USGS provides science on natural hazards, water, energy, minerals, ecosystems, and the impacts of climate and land-use change. Learn more at usgs.gov.
