In October, 2012, the U.S. Geological Survey (USGS) announced a new generation of the National Geologic Map Database, the index to United States maps. It has resulted from a partnership between the USGS and the AASG, the Association of American Geologists. Its antecedent directed searchers to regional map depositories, but now many maps and publications are freely available for downloading. Some maps must still be purchased or otherwise obtained.
The NGMBD makes widely available a national archive of standardized maps. The project was authorized by the Geologic Mapping Act of 1992. The collection is comprised of >90,000 maps from >600 publishers.
There are 4 main avenues: the catalog, the lexicon, the map interface and the historical topographic map collection. The lexicon has stratigraphic information – geologic names, charts, time scales, and guidelines. “Significant publications” are linked to the geologic terms. The lexicon is also referred to as Geolex, the geological time scale, which is still being adjusted to accommodate all the additional geological scholarship and knowledge. Epochs are not yet searchable until the migration of the originally-reported (in the literature) time scales can be reassigned to the present scheme.
The homepage prominently displays keyword searching — by title, author, or map number. Theme limits to select from include: Geology, Geophysics, Marine, Resources (Natural), or Hazards. The “Other” category includes Geochemistry, Geochronology and Paleontology.
One may search by State, Territory or County, by map scale, or by latitude and longitude. Publication date(s) are limitable and formats, too: in paper, available online, with map preview, GeoTiff/ Google Earth KMZ or GIS vector data. One may search by publisher, which besides USGS and AASG includes other government agencies, societies, universities, and the private sector. Mousing/browsing with the cursor over maps will produce the reference from which the map is taken.
A catalog search on Delaware Water Gap produces 5 maps. Here are the 2 largest scale maps:
Bayley, W.S., 1941, Pre-Cambrian geology and mineral resources of the Delaware Water Gap and Easton quadrangles, New Jersey and Pennsylvania: U.S. Geological Survey, Bulletin 920, scale 1:62,500.
Willard, Bradford, 1938, A Paleozoic section at Delaware Water Gap: Pennsylvania Geological Survey, General Geology Report 11, scale 1:83,368.
In addition to the “floppy disk” icon, there is also a globe icon to indicate GIS data.
Sample geologic map — Paleozoic section at Delaware Water Gap
There are 44 topo maps of the Delaware Water Gap. Notice the sliding scale at the top to select dates.
TopoViews show the many and varied older maps which display former names of natural and cultural features. There is a 10-minute introduction to TopoView on YouTube.
This TopoView portion of the database is also part of the National Map, at nationalmap.gov.
PDF printing can be “screen optimized”, “print optimized” or via (trademarked) GeoTIFFs.
Louise Deis, Sci-Tech Reference & Geosciences Liaison, Princeton University, email@example.com