Geology Maps

Geology forms the basis of much of the subject matter about our physical earth. It is the key to a better understanding of the minerals and soils we use to sustain and improve human life on earth. If you have ever wondered why mountains exist, why a river follows a particular course or why some farmland is more productive the answer to your questions will be found in the subject of Geology.

Geologic Map Legends

Land Matters Geologic Maps do not use traditional color based legends. These statewide maps are created from the combination of multiple localized studies. The classification of geologic formations is not standardized and color coded digital representation of these hundreds of classes is not effective.

The best way to present this geologic data is to provide direct access to the details of each individual feature.

Choose the Identify Tool and Click on the geologic feature you would like to know about. The results window will return basic information on the geologic classification you have selected. CLICK the link to read the full details, including map source and unit source references from the USGS

This new map layer is the beginnings of an effort by the USGS to incorporate the Mineral Resources Data System with known verifiable mining features from historic topo maps.

This is a huge and ongoing effort that may help bring the MRDS mines data into a more useable form. Look for changes and additions to these map layers to eventually become the go to source for locational mines and mineral data in the U.S.
Until that process is complete we will be presenting the MRDS mines layer as a companion map layer. Clever researchers will use both layers together to get advanced information on historical mineral resources that are location specific.

These data are part of a larger USGS project to develop an updated geospatial database of mines, mineral deposits and mineral regions in the United States. Mine and prospect-related symbols, such as those used to represent prospect pits, mines, adits, dumps, tailings, etc., hereafter referred to as “mine” symbols or features, are currently being digitized on a state-by-state basis from the 7.5-minute (1:24, 000-scale) and the 15-minute (1:48, 000 and 1:62,500-scale) archive of the USGS Historical Topographic Maps Collection, or acquired from available databases (California and Nevada, 1:24,000-scale only). Compilation of these features is the first phase in capturing accurate locations and general information about features related to mineral resource exploration and extraction across the U.S. To date, the compilation of 400,000-plus point and polygon mine symbols from approximately 51,000 maps of 17 western states (AZ, CA, CO, ID, KS, MT, ND, NE, NM, NV, OK, OR, SD, UT, WA, WY and western TX) has been completed.

Symbol Notes

• When the Mine Symbol is displayed upside down it indicates a mining works feature such as a smelter or tailings pile.
• Adit Symbols are rotated to indicate the compass degree orientation of the adit.
• The Pit Symbol is used to represent Borrow Pits, Prospects or other minor surface workings.

This map layer displays the records previously provided in the Mineral Resource Data System (MRDS) of USGS and the Mineral Availability System/Mineral Industry Locator System (MAS/MILS) originated in the U.S. Bureau of Mines, which is now part of USGS.

The MRDS is a large and complex relational database developed over several decades by hundreds of researchers and reporters. While database records describe mineral resources worldwide, the compilation of information was intended to cover the United States completely, and its coverage of resources in other countries is incomplete.

The content of MRDS records was drawn from reports previously published or made available to USGS researchers. Some of those original source materials are no longer available.

The information contained in MRDS was intended to reflect the reports used as sources and is current only as of the date of those source reports. Consequently MRDS does not reflect up-to-date changes to the operating status of mines, ownership, land status, production figures and estimates of reserves and resources, or the nature, size, and extent of workings. Information on the geological characteristics of the mineral resource are likely to remain correct, but aspects involving human activity are likely to be out of date.

Collected over many decades, this information is highly variable in quality. Currency of individual records is variable as well, so it is likely that some information will be found to be out of date. This is a subject of continuing refinement by the USGS and its cooperators.

Collected and reported by numerous diverse people, the descriptions provided are not highly consistent in structure or terminology. Recent revision of the MRDS database has begun to address this issue, and the present database digest contains fields chosen for their general consistency, though much work remains to be done. The database is generally sparse; many records have no information for a given field. A few fields required for proper processing are complete throughout.

Positional information is highly variable. In the best cases this information was provided by plotting the location on a 7.5 minute topographic map, however many records were located on the basis of published reports containing imprecise or scant information on the specific geographic location. Approximately 4000 records have no reliable geographic coordinates, although about 114 of those have other locational information systematic enough to warrant placement within the controlled vocabulary used to select data for analysis on the web.

Symbol Notes

• Each point represents a different MRDS entry.