Finding Geologic Maps Online

New (or New to Me) from the USGS

Try finding a geologic map of a specific location, and you may run into some trouble.  Not because these maps don’t exist, or because they aren’t online (many of them are), they are just very tricky to find.

The recently updated Geologic Map of North America
The recently updated Geologic Map of North America (2005)

Traditionally, users needed to be able to search for a term that describes the geographical area covered.  Sometimes this is straightforward:  “New York State” or “North America”.  But sometimes it can get confusing: if you would like geologic information about Chautauqua County in New York State, would the New Your State map give you enough detail?  What about a geologic map of Western New York, or the Appalachian low-lands, or the Lake Erie Plain?  There are many, many ways to describe a geographical area in words, often making it difficult to find what you want.

The National Geologic Map Database Data Portal from the USGS attempts to take the guesswork out of this, by allowing users to use a map of the United States to identify the area they need information on, and connect them to a relevant geologic map (either online or in print).

It is still a bit quirky (it is still labeled a prototype) but it is a huge step in the right direction for ease of use.

The National Geologic Map Database Catalog can also be searched in a more traditional manner, allowing users to locate print and online maps.

Additional resources for geologic maps.

  • has a fairly good page linking to images of state geologic maps.  Some of the links don’t work anymore, but those that do images could give users a good overview of state geology.
  • Texas A&M University Library has digitized the Geologic Atlas of the United States, a series of maps and information published by the USGS between 1894 and 1945.  These maps sets offer great detail, in an easy to use online interface, although they are older.
  • The OneGeology Portal is a world-wide project hoping to provide easy online access to geologic map information from around the globe.  It is a partnership of national geologic surveys.  Additional information about the project can be found here.

Of course, all of this assumes that you are simply looking for an image of a map.  If you are looking for GIS geologic data, that is a whole different story!