Since geologic maps were first constructed in the late 18th and early 19th centuries, they have played a fundamental role in understanding the history of the Earth and providing the information needed to solve practical land-use problems, such as ground-water quantity and quality; earthquake, volcano, landslide, and flooding hazards; energy and mineral resources; urban development; and ecosystem and wetlands health.
Early Years—Mapping the Nation
When the USGS was established in 1879, it was assigned the task of "classification of the public lands and examination of the geological structure, mineral resources and products of the national domain." The Survey's Organic Act specifically mentioned geologic and economic maps among the expected products of these investigations.
In 1879, more than half a dozen State Geological Surveys were already actively engaged in geologic mapping; some had been active for more than 50 years. Predecessors of the USGS, which include the Congressionally funded surveys by Clarence King, Ferdinand V. Hayden, and John Wesley Powell of the 1860s and 1870s, also produced reconnaissance geologic maps of large tracts in the American West.
After the establishment of the USGS, there was sharp disagreement as to whether its work was to be limited to the public lands of the West or whether it should extend to the entire United States. This was resolved in 1882 when, at the instigation of then Director John Wesley Powell, Congress authorized the Survey to "continue preparation of the geological map of the United States." Powell interpreted this as authorization for extending the Survey's geologic mapping throughout the Nation. Although Powell construed "preparation of the geological map of the United States" to require the preparation of a uniform series of geologic maps of the entire country, it is doubtful that this is what the Congress intended. The first step in this task was to establish the Geologic Atlas of the United States. The atlas was to consist of a series of folios in a standard format, each containing topographic, geologic, and other maps and illustrations and text describing the geology of a particular quadrangle.
The first of these folios, which covered the Livingston Quadrangle, MT, was published in 1894. By the Survey's 25th anniversary in 1804, 106 folios had been published. However, folio mapping ultimately foundered in the face of increasing cost and decreasing interest and support. The last folio, which covered the Holidays and Huntington quadrangles, PA, was published in 1945, but was based on fieldwork started in 1908!
With the demise of the folio series, the concept of a uniform series of geologic maps covering the entire Nation was effectively abandoned, although it persisted in Survey folklore for decades. Efforts to revive it included the establishment of the Geologic Quadrangle (GQ) map series in 1949 and the efforts to produce nationwide 1:250,000-scale geologic maps that began in the 1960s.
Era of Specialization
Efforts to produce an uniform series of maps of the Nation was based on the assumption that a detailed, high-quality geologic map of an area could depict all facets of its geology and address all its geologic problems. As problems became more diverse and data needed became more specialized, it was recognized that there is no such thing as an all-purpose geologic map. Special needs required maps with special emphasis. USGS geologic mapping was increasingly focused on areas of particular economic interest, areas of special federal concern, and areas of critical scientific interest.
Some early examples of more focused geologic mapping include:
- Reconnaissance mapping in the early 1920's that led to recognition of the petroleum potential of the Arctic Slope of Alaska and the establishment of the Naval Petroleum Reserve 4. In the 1950's, more detailed mapping helped site the well that produced the first petroleum from the Arctic Slope.
- Mapping of the Colorado Plateau to assess its uranium resources during the beginning of the Cold War.
- Detailed mapping of the Nevada Test site to help study the effects of nuclear explosions and assure their containment underground after the Treaty on the Non-Proliferation of Nuclear Weapons entered into force in 1970.
- Major geologic mapping efforts in Kentucky, Massachusetts, and Puerto Rico largely funded by the States and Commonwealth.
- Geologic mapping of areas under consideration for wilderness status as required by the Wilderness Act of 1964.
National Geologic Mapping Act of 1992
This Act, with its reauthorizations in 1997, 1999, and 2009 recognized the importance of geologic mapping in utilization of mineral resources, effective stewardship of the environment, safe disposal of domestic and industrial waste, and mitigation of natural hazards. It established a program under the leadership of the USGS, which obtained advice from other federal agencies, state agencies, academia, and the private sector to help meet these needs. The USGS role includes mapping to meet requirement of other federal agencies, and maintenance of data bases on stratigraphy, geochronology, paleontology, and several other mapping related topics. The state role includes more detailed mapping to meet state and local needs, and the academic role emphasizes the training of students in geologic mapping. Although this Program has never been funded at the levels anticipated by the Act, it has had a significant impact on efforts to meet the mapping needs of the Nation.
Geologic Mapping Today
Currently, much USGS geologic mapping focuses on practical aspects of geology. These include distribution of active faults that pose earthquake threats to population centers or critical installations; distribution of materials that are particularly subject to landsliding or slope failure; distribution of volcanic deposits that help delineate areas at risk from volcanic eruptions; studies of the movement of water, petroleum, natural gas, and waste (including radioactive) through geologic materials; and studies of surficial deposits that record climatic changes over time. All of these use information found in geologic maps.
Today geologic mapping is alive and well in the USGS and is commonly facilitated by satellite imagery, aerial photography, global positioning system GPS technology, and geographic information systems GIS-based cartography. But in the end, all geologic mapping comes down to geologists wearing boots and walking along the ground with a compass, pick, notebook, and hand lens, just as they did in Powell's day.