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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 19 recordsLinked to original sources
USGS2007

Mineral resource of the month: niobium (columbium)

It’s not just diamonds associated with conflict in Africa. Coltan, short for columbite-tantalite (a blend of niobium — also called columbium — and tantalum minerals), is linked with the recent conflicts in the Congo that involved several African countries. The metallic ore, which is processed to separate out niobium and the very valuable tantalum (see Geotimes, August 2004), is believed to be smuggled out and sold to help finance the armed conflicts.

Geotimes↗
USGS2004

Coal and cremation in ancient Peru

After my visit to the adobe-walled archaeological site of Chan Chan, near Trujillo in northern Peru in the summer of 2000 (Geotimes, August 2003), my guide asked if I would like to see the metallurgical furnaces used by the Chimú, ancient residents and master metalsmiths of the region. Chan Chan was the capital of the Chimú Empire (A.D. 1100-1400) and the largest pre-Columbian city in the Americas. These furnaces, my guide explained, were where Andean gold, silver and copper ores were smelted and fabricated into jewelry, masks and plates sought by the Spaniards. We left the main part of the complex, followed a dusty trail, and arrived at a site marked by fresh-looking, redbrown, clinker-like debris.

Geotimes↗
USGS1981

7.3 quake in Algeria reviewed.

A team from the U.S. Geological Survey studies the surface effects of the Oct. 1980 10 shock, whose epicenter was west of Algiers, near the African Plate boundary. -Authors

Geotimes↗
USGS2002

Global petroleum resources: A view to the future

It is necessary to periodically reassess petroleum resources, not only because new data become available and better geologic models are developed; but also because many non-geologic factors determine which part of the crustal abundance of petroleum will be economic and acceptable over the foreseeable future. In 2000, the U.S. Geological Survey completed an assessment of the world's conventional petroleum resources, exclusive of the United States. This assessment is different from those before it: Overall the 2000 assessment of potential petroleum resources is higher than previous assessments, largely because it is the first USGS world assessment to include field growth estimates. Based on a thorough investigation of the petroleum geology of each province, the assessment couples geologic analysis with a probabilistic methodology to estimate remaining potential. Including the assessment numbers for the United States from USGS and the Minerals Management Service (MMS), the world's endowment of recoverable oil - which consists of cumulative production, remaining reserves, reserve growth and undiscovered resources - is estimated at about 3 trillion barrels of oil. Of this, about 24 percent has been produced and an additional 29 percent has been discovered and booked as reserves. The natural gas endowment is estimated at 15.4 quadrillion cubic feet (2.5 trillion barrels of oil equivalent), of which only about 11 percent has been produced and an additional 31 percent has been discovered and booked as reserves. The USGS assessment is not exhaustive, because it does not cover all sedimentary basins of the world. Relatively small volumes of oil or gas have been found in an additional 279 provinces, and significant accumulations may occur in these or other basins that were not assessed. The estimates are therefore conservative.

Geotimes↗
USGS2003

Geomedia: Mapping Colorado at a fine scale

Currently, only 24 percent of Colorado's spectacular geology has been mapped at the fine scale of 1:24,000. At the same time, the state hosts many geologic hazards. Most maps of Colorado are at much broader scales, failing to show detail of basic geology crucial to safe engineering and building practices in a state that had the third-fastest-growing population during the 1990s. And the 2000 Census showed that the state, despite some economic woes, remains one of the fastest growing. Detailed geologic maps also aid the mineral industries that help fuel such growth. Since 1992, the Colorado Geological Survey (CGS) has mapped 1:24,000-scale quadrangles in high-impact areas under the STATEMAP component of the National Cooperative Geologic Mapping Program. In 2002, CGS completed its 43rd geologic quadrangle map. The long-range plan for the state is to complete 116 high-priority quadrangles in the next 15 years. The survey's approach is to select rapidly growing areas with relatively high potential for hazards and map contiguous quadrangles. In addition to mapping bedrock, CGS geologists have mapped the Quaternary deposits at the surface. Understanding these deposits is extremely important for implementing sound engineering practices because of potential for subsidence and landslides. The CGS mapping has not only yielded information about potential hazards, but also advanced scientific understanding of the state.

Geotimes↗
USGS2003

Mineral resources of Peru's ancient societies

Northern Peru has an exceptionally rich archaeological heritage that includes metalwork, ceramics and textiles. The success of at least a half-dozen pre-Columbian societies dating back 3,000 years and subsequent Spanish colonization in the 1400s has rested on the effective use of northern Peru's abundant resources. In the summer of 2000, my son Matt and I learned about that connection firsthand by volunteering at the Santa Rita B archaeological site in the Chao Valley near Trujillo in northern Peru. Riding donkey-back through the Andes and talking with local people, we got our hands dirty in the rich archaeology and geology of the area. We were able to correlate mineral occurrences to their various roles in society - opening a window into the region's fascinating past. From construction to metallurgy, pre-Columbian societies flourished and advanced because of their understanding and use of the available mineral resources.

Geotimes↗
USGS2004

Tracking contaminants down the Mississippi

The Mississippi River and its last major downstream distributary, the Atchafalaya River, provide approximately 90 percent of the freshwater input to the Gulf of Mexico. Analyses of sediment cores using organic and inorganic tracers as well as bethic foraminifera appear to provide a reliable record of the historic variability of hypoxia in the northern Gulf of Mexico over the past few centuries. Natural variability in hypoxic events may be driven largely by flooding cycles of El Nin??o/La Nin??a prior to recent increases in nutrient loading. Specifically, large floods in 1979, 1983, 1993 and 1998, compounded with the widespread use of fertilizers, also appear at least partially responsible for the recent (post-1980) dramatic increase of hypoxic events in the Mississippi Bight.

Geotimes↗
USGS2005

Earthquakes: Predicting the unpredictable?

The earthquake prediction pendulum has swung from optimism in the 1970s to rather extreme pessimism in the 1990s. Earlier work revealed evidence of possible earthquake precursors: physical changes in the planet that signal that a large earthquake is on the way. Some respected earthquake scientists argued that earthquakes are likewise fundamentally unpredictable. The fate of the Parkfield prediction experiment appeared to support their arguments: A moderate earthquake had been predicted along a specified segment of the central San Andreas fault within five years of 1988, but had failed to materialize on schedule. At some point, however, the pendulum began to swing back. Reputable scientists began using the "P-word" in not only polite company, but also at meetings and even in print. If the optimism regarding earthquake prediction can be attributed to any single cause, it might be scientists' burgeoning understanding of the earthquake cycle.

Geotimes↗