Nitrogen isotope ratios of ammonium and nitrate ions from soil and water samples can be analyzed reproducibly with an experimental error of approximately +/-1 parts per thousand (ppt). Two isotopic ranges of soil nitrate are found in the soils of southern Runnels County, Texas. Nitrate from the decomposition of animal waste nitrogen has a dN15 of +10 ppt to +22 ppt. The isotopic ratio is controlled by the volatilization of isotopically light ammonia gas during the decomposition of urea in urine.

Knowledge of the regional sand distribution and its relationship to formation temperature and pressure is a preliminary step in evaluating the geothermal resources of the Frio Formation. At depths generally greater than 7,000 feet, the sands and shales of the Frio Formation are overpressured and undercompacted. The insulating effect of these overpressured and undercompacted sediments results in the accumulation of subsurface heat and, thus, high temperature water.

Nelson and others (1962) define a bank as " ... a skeletal deposit formed by organisms which do not have the ecologic potential to erect a rigid wave-resistant structure." They explain that a bank may have any geometry. The principal types or end members are biostromes which are thin, flat to lenticular deposits, or bioherms which are mounds.

Historical monitoring along Galveston Island records the type and magnitude of changes in position of the shoreline and vegetation line and provides insight into the factors affecting those changes. Documentation of changes is aided by the compilation of shoreline and vegetation line position from topographic maps, aerial photographs, and coastal charts of various vintages.