GEOLOGY OF TEXAS Engineering Geology
In common with most engineering activities, the field of engineering geology, by nature, focuses on more site-specific issues than other sub-fields of geology. Engineering geology starts with a site and then investigates how the area surrounding it might affect that site. For example, a building foundation must rest upon a particular type of soil, sediment, consolidated or other type of hard rock. How that foundation, loaded by the building constructed above it, will behave in response to the natural foundation below it is a good example of the type of issues investigated in engineering geology.
Because the geology (or the characteristics of the earth materials in outcrops and in the subsurface) is common to all sub-fields, we present here a summary of the geology of Texas, as follows:
 
Average Annual Texas Precipitation & Average Annual Net Lake Evaporation |
Engineering Geology and Natural Resources
Generalized Areas of Known or
Potential Mineral Reserves |
Mining
Uranium Resources
Upper Eocene and Miocene fluvial sediments host Tertiary-age "roll-front" uranium deposits in south Texas, which may extend into south-east Texas. Uranium mining (both open pit and in-situ mining) and yellow-cake production were initiated in the 1970's and have continued sporadically since then. The typical "roll-front" shown in the above photo of an open-pit uranium mine forms the basis of exploration methods.
Lignite/Coal Resources
This basin has over the past 20 years developed an important role in lignite exploration and mining. Centered in Northeast Texas, a number of companies are currently mining lignite. Production for 1996 was approximately 53 million tons. This makes Texas the 5th largest coal producer in the nation, The lignite is mined from the Wilcox Group (Paleocene-Eocene) and other Tertiary fluvial units.
In Texas, about 98% of all lignite mined is used for electric power generation. Approximately 27% of the electricity generated in Texas is from lignite. Texas imports 24% of its coal from several western states and is the largest consumer of coal in the nation, burning 93 to 94 million tons per year. According to the Bureau of Economic Geology of Texas, the demonstrated reserve base of surface mineable lignite is sufficient to fuel electric generation for at least 100 years. The mining industry in Texas is a mature and healthy industry, providing substantial economic support to the state's economy.
Geothermal Resources
Geopressured geothermal resources were identified in the 1970's and attempts at development and commercialization were made with only limited success. This resource awaits development.
Engineering Geology and Environmental Issues
Texas, like many states, has complex environmental issues, not the least of which is the water supply. Texas is fortunate to have abundant ground water and surface water, and only recently has Texas begun to sort out the many issues involved, such as ownership rights and appropriate use guidelines. The use of low-quality surface water for irrigation and industrial cooling, and of high quality, low cost ground water for drinking water have only begun to be implemented in the U.S. and in Texas.
Water Supplies
In a population of rapid growth, nearly full employment, and a free economy, Texas residents debate the age-old conflict between industrial development and the status quo, resource utilization and appropriate management, and associated environmental issues. But population growth and economic development, coupled with a climate in which surface-water resources are scarce, have imposed real and potential water-supply problems in many areas of Texas. In much of Texas, available surface storage capacity in existing reservoirs will barely be sufficient to meet water demands of continued industrialization and urban development, especially during critical droughts which are common occurrences over the long term.
Extensive development of the readily available ground water has progressed rapidly over the past 20 years but has resulted in several problems, some local in nature, while others are more widespread. Problems of water quality, both from natural and man-made causes (e.g., nitrates), are expected to affect the suitability for use of water from portions of Texas' aquifers in the future. Natural pollution, primarily sodium chloride, results from salt springs and salt flats within drainage areas of the basins. In some areas, this problem has been aggravated to some extent by oil and gas exploration and production activities. Mining has also been indicated as contributing to pollution. Balancing resources and local needs to maintain economic growth and development are the primary goals in Texas.
More than 50 percent of Texas in underlain by seven major aquifers and 16 minor aquifers. Because of industrial and urban development, long-term use of ground water is lowering water levels to the extent costs of production are increasing rapidly. Surface-water reservoirs are being developed in south Texas, and elsewhere, to offset the foreseeable problems of the future.
Geologic Hazards
Texas is fortunate to exist in a region low in seismicity. However, earthquakes, albeit of low magnitude, have and will occur again in the future in Texas (here). The cause of these earthquakes has been related to oil & gas and ground-water production, and structural readjustment in active salt domes, but most likely to shallow basement movement, and, in the Rio Grande River area, to deep seated, structural “unzipping”.
University of Texas scientists operate seismograph stations in Hockley, TX, north of the northern suburbs of Houston, Texas, and (in collaboration with colleagues at Texas Tech) in Junction, TX. Currently they are working to fund and install several more seismograph stations in Texas. This network, called TexSeis, would provide Texas with modern seismographic facilities that are comparable to those in other states having one or more large cities.
At the Hockley link, you can learn more about what goes on at a typical seismograph station. There is also a picture tour of the Hockley facility, which is 600 meters below the Earth's surface in a salt mine.
References:
Spearing, D., 1991, Roadside Geology of Texas, Mountain Press Publishing Company, Missoula, MT, 418 p.
Fisher, W. L. , and W. E. Galloway, 1983, Potential for Additional Oil Recovery in Texas, Bureau of Economic Geology Geological Circular 83-2, pp.6-7.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States , Chapter 2: Trend Exploration-Uranium, Houston Geological Society, pp.45-66.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States, Chapter 6: Frontier Exploration-Lignite, Houston Geological Society, pp.125-159.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States, Chapter 12: Trend Exploration-Geopressured Geothermal Energy, Houston Geological Society, pp. 251-273.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States, Chapter 4: Environmental Considerations-Uranium, Houston Geological Society, pp. 83-109.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States, Chapter 9: Environmental Considerations-Lignite, Houston Geological Society, pp. 193-202.
Campbell, M. D., et al., 1977, Geology {and Environmental Impact of} Alternate Energy Resources in South-Central United States, Chapter 14: Environmental Considerations-Geopressured Geothermal Energy, Houston Geological Society, pp. 297-336.
Evans, T. J., 1974, Bituminous Coal in Texas, Bureau of Economic Geology Handbook 4, 65 p.
Kaiser, W. R., et.al., 1980, Lignite Resources in Texas , Bureau of Economic Geology Report of Investigations No. 104, 52 p.
Jones, D. C., 1973, An Investigation of the Nitrate Problem in Runnels County, Texas, Texas Water Development Board, EPA-R2-73-267, June, pp.6-7.
Brown, L. F., et al., 1976, Environmental Geologic Atlas of Texas Coastal Zone- Corpus Christi Area, Bureau of Economic Geology, 123 p.
Bebout, D. G., et al., 1976, Geothermal Resources, Frio Formation, Upper Texas Gulf Coast,, Bureau of Economic Geology Geological Circular 76-3, 47 p.
Dorfman, M., and R. O. Kehle, 1974, Potential Geothermal Resources of Texas, Bureau of Economic Geology Geothermal Circular 74-4, 33 p.
Smith, G. E., et al., 1982, Regional Hydrodynamics and Hydrochemistry of the Uranium-Bearing Oakville Aquifer (Miocene) of South Texas, Bureau of Economic Geology Report of Investigations No. 124, 31 p.
Galloway, W. E., et al., 1982, Depositional Framework, Hydrostratigraphy, and Uranium Mineralization of the Oakville Sandstone (Miocene), Texas Coastal Plain, Bureau of Economic Geology Report of Investigations No. 113, 51 p.
Collins, E. W., et al., 1980, Quaternary Faulting in East Texas, Bureau of Economic Geology Geological Circular 80-1, 20 p.
Anon., 1984, Water for Texas: A Comprehensive Plan for the Fututre, November, Texas Dept. of Water Resources GP-4-1, 72 p.
Ashworth, J. B., and J. Hopkins, 1995, Aquifers of Texas, Texas Water Development Board Report 345, November, 69 p. |
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