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USGS2001

Finding Your Way with Map and Compass

A topographic map tells you where things are and how to get to them, whether you're hiking, biking, hunting, fishing, or just interested in the world around you. These maps describe the shape of the land. They define and locate natural and manmade features like woodlands, waterways, important buildings, and bridges. They show the distance between any two places, and they also show the direction from one point to another. Distances and directions take a bit of figuring, but the topography and features of the land are easy to determine. The topography is shown by contours. These are imaginary lines that follow the ground surface at a constant elevation; they are usually printed in brown, in two thicknesses. The heavier lines are called index contours, and they are usually marked with numbers that give the height in feet or meters. The contour interval, a set difference in elevation between the brown lines, varies from map to map; its value is given in the margin of each map. Contour lines that are close together represent steep slopes. Natural and manmade features are represented by colored areas and by a set of standard symbols on all U.S. Geological Survey (USGS) topographic maps. Woodlands, for instance, are shown in a green tint; waterways, in blue. Buildings may be shown on the map as black squares or outlines. Recent changes in an area may be shown by a purple overprint. A road may be printed in red or black solid or dashed lines, depending on its size and surface. A list of symbols is available from the Earth Science Information Center (ESIC).

Fact Sheet↗
USGS2002

Estimated flood flows in the Lake Tahoe basin, California and Nevada

Lake Tahoe, the largest alpine lake in North America, covers about 192 square miles (mi 2 ) of the 506-mi 2 Lake Tahoe Basin, which straddles the border between California and Nevada (Fig. 1). In cooperation with the Nevada Department of Transportation (NDOT), the U.S. Geological Survey (USGS) estimates the flood frequencies of the streams that enter the lake. Information about potential flooding of these streams is used by NDOT in the design and construction of roads and highways in the Nevada portion of the basin. The stream-monitoring network in the Lake Tahoe Basin is part of the Lake Tahoe Interagency Monitoring Program (LTIMP), which combines the monitoring and research efforts of various Federal, State, and regional agencies, including both USGS and NDOT. The altitude in the basin varies from 6,223 feet (ft) at the lake's natural rim to over 10,000 ft along the basin's crest. Precipitation ranges from 40 inches per year (in/yr) on the eastern side to 90 in/yr on the western side (Crippen and Pavelka, 1970). Most of the precipitation comes during the winter months as snow. Precipitation that falls from June through September accounts for less than 20 percent of the annual total.

California, Nevada↗
USGS1996

Programs in Ohio

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Fact Sheet↗
USGS1999

North Dakota

North Dakota prairies contain numerous wetlands. The complex functions of these prairie wetlands have been of interest for decades. The hydrology, water chemistry, and biological characteristics of these wetlands are highly variable because of extreme warm/cold and wet/dry conditions. The U.S. Geological Survey (USGS) has been conducting studies (fig. 1) to gain insight into the functions of the prairie wetlands. The USGS Northern Prairie Wildlife Research Center in Jamestown has maintained an active wetland research program since the mid-1960’s. Current work in North Dakota began in 1978, and focuses on the response of biological communities to climate-induced variations in hydrology and chemistry, and on evaluating the success of previously drained wetlands restored under the Conservation Reserve Program (CRP) and on similar lands. The information provided from this long-term study has provided the bulk of our knowledge about prairie wetlands, and has provided land managers with valuable information to manage the Nation’s prairie wetland resource.

North Dakota↗
USGS2000

Mount St. Helens - From the 1980 eruption to 2000

Mount St. Helens, Washington, is the most active volcano in the Cascade Range. Its most recent series of eruptions began in 1980 when a large landslide and powerful explosive eruption created a large crater, and ended 6 years later after more than a dozen extrusions of lava built a dome in the crater. Larger, longer lasting eruptions have occurred in the volcano's past and are likely to occur in the future. Although the volcano seems to have returned to a period of quiet, scientists with the U.S. Geological Survey and University of Washington Geophysics Program continue to closely monitor Mount St. Helens for signs of renewed activity.

Washington↗
USGS2002

Occurrence of bacteria in Blue Marsh Lake and selected tributaries, Berks County, Pennsylvania: September-October 2001

The Commonwealth of Pennsylvania has water-quality standards that limit the number of specific bacteria in water that is considered safe for recreational use. Bacteria such as fecal streptococci, fecal coliforms, and Escherichia coli (E. coli ) are used to assess recreational water quality because they usually live in the intestines of warm-blooded animals. Fecal indicator bacteria commonly are associated with waterborne disease-causing organisms (pathogens). These indicator bacteria are used routinely as a measure of the quality of water for recreational activities such as swimming, boating, and water skiing. If the indicator bacteria are present, effective measures could be taken to prevent the transmission or epidemic outbreak of waterborne diseases as a result of contamination of these waters from human or animal waste. Blue Marsh Lake is on Tulpehocken Creek in Berks County, Pa., and drains a largely agricultural basin. Land use in the basin is approximately 60 percent cropland, and 85 percent of the farms are livestock and poultry farms. The potential sources of fecal bacteria are: geese that inhabit the recreational areas of the lake, humans that visit the Dry Brooks Day Use Area (swimming area), and farm animals, wastewater facilities, and household septic systems in the basin (bacteria from these sources could enter the lake through tributaries). To meet the recreational water-quality standard, lake water may not have more than 200 colony-forming units (CFU) of fecal coliforms per 100 milliliters (mL). During the week of July 23, 2001, data collected by the U.S. Army Corps of Engineers (USACE) at the swimming area at Blue Marsh Lake showed concentrations of fecal coliforms in the water exceeding the standard. To determine the extent of elevated concentrations of fecal indicator bacteria, further study of the lake and selected tributaries was needed.

Pennsylvania↗
USGS2003

Rapid-deployment data-collection networks for wildland fire applications

Rapid-deployment data-collection networks were developed for wildland fire applications like the Missionary Ridge Fire. The Missionary Ridge Fire began June 9, 2002, near Durango, Colorado. An Interagency Burned Area Emergency Rehabilitation (BAER) Team arrived in Durango, Colorado, to assess the fire. At that time, the fire had burned over 70,000 acres and was still actively burning. The fire was contained on July 14, after consuming 73,400 acres. The team was charged with assessing the potential postfire effects on health and safety, and risks to property and natural resources. From this assessment, the team would prescribe treatments on Federal lands to reduce damage to the values at risk from the burned watersheds. The team found that human life was at risk early in their assessment.

Colorado, South Dakota↗
USGS1999

Ohio

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Fact Sheet↗
USGS2000

U.S. Geological Survey World Wide Web Information

The U.S. Geological Survey (USGS) invites you to explore an earth science virtual library of digital information, publications, and data. The USGS World Wide Web sites offer an array of information that reflects scientific research and monitoring programs conducted in the areas of natural hazards, environmental resources, and cartog-raphy. This list provides gateways to access a cross section of the digital information on the USGS World Wide Web sites.

Fact Sheet↗
USGS2001

Assessment of undiscovered oil and gas resources in Central and South America

The U.S. Geological Survey recently completed an assessment of undiscovered conventional oil and gas resources in 130 selected petroleum provinces of the world (USGS, 2000). Of these 130 provinces, 23 are in South America, Central America, and the Caribbean area (fig. 1). The assessed provinces range from established petroleum provinces with long histories of production such as the Maracaibo Basin to frontier provinces with little or no petroleum production such as the Guyana-Suriname Basin. Not all provinces with historic production or potential production were assessed for the USGS 2000 Assessment. At present we are assessing many of the remaining oil and gas provinces in Central and South America. In each province we (1) geologically defined total petroleum systems, (2) defined assessment units within total petroleum systems, and (3) assessed the volume of undiscovered conventional oil and gas in each assessment unit. We defined 26 total petroleum systems and 55 assessment units in the 23 provinces.

Fact Sheet↗
USGS2003

Drought conditions in Utah during 1999-2002: A historical perspective

Utah’s weather is prone to extremes – from severe flooding to multiyear droughts. Five major floods occurred during 1952, 1965, 1966, 1983, and 1984, and six multiyear droughts occurred during 1896-1905, 1930-36, 1953-65, 1974-78 (U.S. Geological Survey, 1991), and more recently during 1988-93 and 1999-2002. The areal extent of floods generally is limited in size from one to several watersheds, whereas droughts generally affect most or all of the state. Southern Utah, in particular the Virgin River drainage basin, began experiencing drought conditions during the winter of 1998-99. By 2000, drought conditions were evident throughout all of Utah. The current drought (1999-2002) is comparable in length and magnitude to previous droughts; however, with population growth and increased demand for water in Utah, the general effect is more severe.

Utah↗