best use and (or) control of developments in the subsurface. This computer program carries out many simulations of a field system, readjusting the control variables (that is, the position and pumping rate of wells) on each simulation until an optimal development scheme is found under the desired conditions.

The goal of developing analytical hydrologic tools in the form of an intelligent simulator that automatically organizes itself to simulate a particular subsurface system from raw data is close to realization. This advance is based on significant developments in model identification and in model parameter-estimation methods. These developments also have direct application to the efficient design of networks for collecting the data on which the analysis of subsurface systems is based.

LAKE HYDROLOGY RESEARCH

Lakes are an important national resource used for water supply, for cooling water for industries and utilities, as a source for food,

and for recreation. Lakes are hydrologically complex, and they are often mismanaged because their function within the hydrologic system is not well understood. To address this problem, the U.S. Geological Survey initiated a program of research on lakes in different climatic and geologic settings throughout the United States. A few recent results of that research follow.

seepage

Numerical modeling of ground-water movement near lakes indicates that to and from lakes is highly dynamic and dependent on the timing and areal distribution of recharge to ground water. The common concentration of recharge directly adjacent to a lakeshore causes increased rates of seepage to the lake very quickly following, or even during, a period of rainfall. This process is particularly important along areas of a lakeshore that might ordinarily have seepage out of the lake, because the concentrated recharge reverses the direction of seepage and therefore causes ground water to seep into the lake. This phenomenon has been observed at many locations in the United States, such as Mirror Lake, N.H., Williams Lake, Minn., Cottonwood Lake, N. Dak., and Island Lake, Nebr.

In addition to being concentrated directly adjacent to lake shorelines, ground-water recharge is also frequently concentrated in depressions in upland areas between lakes. In the sand hills region in western Nebraska, for example, water table mounds occur in uplands characterized by many topographic depressions because of the greater opportunity for recharge in those depressions. In contrast, where there are no depressions in the upland, troughs on the water table surface occur because recharge is minimized. The normal seepage of water to and from lakes differs in this region in that water seeping from a lake usually does not move to adjacent lower lakes because of the presence of these water table mounds or troughs.

Knowledge of concentrated recharge near lakeshores or in topographic depressions is also important for understanding groundwater quality. For example, in the Cottonwood Lake area of North Dakota, frequent reversals of the direction of ground-water flow between adjacent wetlands increases the contact time of ground water with the rock matrix and results in increased salinity in local areas of the ground-water system. This increased salinity ultimately affects the quality of water in the wetlands that the ground water seeps into. Also, these differences in the quality of ground water seeping into a lake or wetland commonly affect the distribution of aquatic plants and microscopic animals living on the bottom of the lake or wetland. In some cases, the chemical quality of ground-water seepage is indicated by the presence of aquatic organisms in the lake or wetland.

Detailed study of seepage patterns in lakebeds has also resulted in a greater understanding of the impact of transpiration by nearshore upland plants. For example, during drier periods of the year, when ground-water levels are low, nearshore plants often lower ground-water levels to the point where lake water will seep into ground water, even if the regional gradient

of the water table is toward the lake.

Research on the interaction of lakes and ground water is important for understanding the water balance of lakes, the chemical characteristics of lakes, and the distribution of aquatic plants and microscopic animals. and plants in lakes, which in turn provide guidance for the successful management of lake ecosystems.

At 2:30 a.m. local time on March 27, 1986, Augustine volcano erupted in Cook Inlet, 180 miles southwest of Anchorage, Alaska. The Landsat 5 satellite acquired a Thematic Mapper image of the volcano at 10:46 a.m. Ash falling throughout the area curtailed air traffic, power usage, and business activities. The U.S. Geological Survey monitors Augustine and the 51 other active volcanoes in the United

States. (Photograph courtesy of Earth Observation Satellite Company, Lanham, Md.)

MISSION AND OUTLOOK

During fiscal year 1986, the Geologic Division of the U.S. Geological Survey continued its programs to assess energy and mineral resources onshore and offshore, to identify and investigate geologic hazards, and to determine the Nation's geologic framework, the geologic processes that shaped it, and their relation to long-term climatic changes.

The articles in this chapter describe some of the most significant accomplishments of the Geologic Division during fiscal year 1986. Although these articles cover only a select few of the Division's activities, they show how basic geologic research simultaneously spurs new developments in the geosciences and provides the basic information required to conduct missions central to the needs of the Nation.

MAJOR PROGRAMS

The Geologic Division program is presented to Congress under five major program headings. A discussion of accomplishments under these subactivities during fiscal year 1986 and the outlook for the future follow.

Geologic Hazards Surveys

A regional earthquake hazard assessment in the Provo-Salt Lake City-Ogden area of Utah was conducted in fiscal year 1986. Efforts with State and local officials to ensure that the results of this study are used to implement hazard reduction practices continue. A similar research effort in the

be installed and calibrated in fiscal year 1987. (See "Predicting the next major earthquake in the Parkfield area of California," p. 12, for more information.)

A study of the effects of recent earthquakes in Mexico and Chile provided data that can be applied to improving knowledge of similar seismic events that may occur in the United States. For example, the study greatly improved understanding of the devastating role that unconsolidated sediments can play in amplifying ground shaking.

Fiscal year 1986 was year of unusual volcanic activity in Alaska and Hawaii (additional information regarding the Alaskan eruptions is found on p. 58). Monitoring and hazard assessments of all volcanically active regions of the Nation continue. Geologic Division scientists also assisted the Office of Foreign Disaster Assistance of the Agency for International Development during the eruption of Nevado del Ruiz in Colombia. (See "International activities," p. 105, for more information.)

Cooperative Federal-State landslide hazards assessment studies were established in fiscal year 1986 with the States of Arizona, Colorado, Idaho, Maine, Nevada, New Mexico, Ohio, Oregon, Utah, and the Commonwealth of Puerto Rico. Probability studies of landslide occurrence in the San Francisco Bay area of California and the Wasatch Front in Utah to identify dominant landslide processes amenable to low-cost landslide hazard reduction and a landslide hazards assessment of the Pittsburgh region of Pennsylvania are also planned.

planned.

Installation of instrumentation for the prototype earthquake prediction experiprototype earthquake prediction experiment at Parkfield, Calif., was continued in fiscal year 1986; additional instruments will

A nationwide survey of geoscience information users conducted by the National Research Council indicated that large-scale general-purpose geologic maps are the

products most in demand by private and public consumers. In response to this survey, the Geologic Framework and Synthesis Program will be redirected to become the National Geologic Mapping Program. Although most of the basic research functions of the former program will be preserved, its emphasis will be shifted to systematic, prioritized geologic mapping. The Federal-State Cooperative Geologic Mapping component of the Geologic Framework and Synthesis Program will be preserved as an element of the National Geologic Mapping Program. Thirty-one Federal-State cooperative projects were underway in fiscal year 1986.

Significant activities under the Deep Continental Studies component of the Geologic Framework and Synthesis Program are addressed in articles on the TransAlaska Crustal Transect and the Salton Sea Scientific Drilling Program (see p. 60, 55). Plans are underway to establish the Deep

(see p. 53). Data previously gathered by programs within the Mineral Resource Survey's subactivity have been used to establish a national geochemical data base for identifying and monitoring areas where soil and water are contaminated. The first step in this plan was to compile existing data; areas where insufficient data exist are being identified, and plans are being developed to implement a schedule of sampling and resampling.

Fiscal year 1986 saw the acquisition of software to produce digital mineral resource assessment maps compatible with land use, census, and other geographic and water information maps produced in other information systems of the Geological Survey. This compatibility will facilitate comparisons of mineralized locations with other social and economic conditions within a geographic area.

Research under the Climate Change Program has established the long-term history of lake-level fluctuations in the United States. The geologic record indicates that historical lake levels are abnormally

low and that the trend from natural variation

indicates a long-term rise in lake levels. These studies illustrate that basic research can be useful in identifying and resolving environmental policy issues associated with potentially significant economic impacts. Geologic Division scientists continue to be

In fiscal year 1986, the Uranium and Thorium Investigations Program began using geologic data to identify areas having high potential for indoor radon hazards. Further information on this effort is contained in this chapter (see p. 38).

In cooperation with the Kentucky Geological Survey, a study to characterize the quantity, quality, and accessibility of lowsulfur coal in eastern Kentucky began. Included in that effort are an economic evaluation of the area's potential for coal production and computer modeling of the coal deposits. This type of study may be expanded to include other coal-bearing areas in the Appalachian region.

of Engineers and other concerned Federal and State agencies in addressing the hazards. created by changing lake levels in areas. such as the Great Lakes, including advising those agencies on the feasibility of mitigation strategies.

Mineral Resource Surveys

The National Mineral Resource Assessment Program is described in this chapter

The Coastal Erosion Program, established in fiscal year 1986, is designed to provide geologic information on the nature, extent, and cause of coastal erosion to the various Federal and State agencies that make decisions pertaining to the arrest and (or) mitigation of coastal retreat and land loss. The current focus of the program is the highly vulnerable coastal segments of the Louisiana barrier island system.

The results of sonar surveying of the sea floor of the Gulf of Mexico and of submarine