Background (Encyclopedia of Global Resources)
Geology is the study of the planet Earth: its composition, origin, and history, and the environmental, biological, chemical, and physical forces outside and within it. As a science, geology grew from the nineteenth century study of natural features, stratigraphy, and fossils in rock outcroppings to a wide variety of scientific subspecialties covering myriad aspects of the planet. Since the early nineteenth century, geology has involved accurate mapping of the Earth’s topography and discovery, study, and exploitation of major mineral deposits around the world.
A guiding principle in geology has been uniformitarianism: geological processes that are observed today are the same as those that occurred in the past and those that will occur in the future. Application of this concept on a planetary scale allows scientists to prospect for minerals using remote-sensing techniques.
Catastrophic events, including meteor impacts, have been deduced from geological deposits and have been credited with causing widespread mass extinctions observed in the fossil record. Identification of the large meteor impact responsible for forming Chesapeake Bay has provided an explanation for recent earthquakes in the region and for the presence of saltwater aquifers in Virginia. Some economic geologists have postulated that the platinum deposit at Sudbury, Ontario, is a meteor impact site from billions of years ago.
The United States...
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Exploration Geology (Encyclopedia of Global Resources)
Exploration geologists focus on the discovery and exploitation of mineral and ore deposits and fossil fuels. stone Age humans found outcroppings of flint and chert with which to make arrowheads and other tools. Eventually, humans moved on to easily worked metals such as copper, tin, silver, gold, and iron. Precious gems have been highly valued for millennia, and new sources for these ores and minerals continue to be found.
Modern industrialized society requires metals for basic construction and manufacturing. The increasing technological demand has moved geological exploration from the California gold rush era of the American West to the worldwide search for uranium for nuclear weapons to the search for rare earth elements for high-tech electronics and lithium deposits for batteries. Geologists in the twenty-first century rarely engage in time-consuming initial field exploration and prospecting, relying on remote sensing from aircraft and satellites to determine where new mineral deposits might be found. Confirmation of mineral deposits and plans for exploitation require geological expertise.
The exploitation of coal, oil, and gas deposits around the world provides vital sources of energy to the billions of people on Earth. Most geologists are employed, usually by governments and private industry, in this aspect of geology.
Coal remains the most important fuel for electric power production worldwide, with...
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Geological Monitoring of Volcanoes and Earthquakes (Encyclopedia of Global Resources)
The devastating Boxing Day tsunami of December 26, 2004, which engulfed Indian Ocean shorelines from Indonesia to East Africa and killed more than 225,000 people, followed an undersea event known as the Great Sumatra-Andaman earthquake. The countries most affected by the tsunami lacked geological monitoring stations. Such a seismological monitoring network could have provided many areas with several hours warning of the impending tsunami and lessened the death toll. The U.S. National Oceanic and Atmospheric Administration operates the Pacific Tsunami Warning System, which warns of potential problems for Hawaii, Alaska, and the Pacific coast of North America.
Volcano monitoring is necessary to warn people of impending eruptions. Erupting volcanoes emit clouds of ash that can be sucked into jet aircraft engines, where the ash liquefies and then deposits a solid glass coating to the rear of the jet turbine. This glass coating interferes with the jet enough to cause the aircraft to crash. Ash problems necessitate closure of airports within the reach of the erupting volcano, and aircraft must be diverted from routes that pass through the ash clouds.
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Environmental Geology (Encyclopedia of Global Resources)
Environmental geologists use a variety of geological, geochemical, microbiological, and hydrological techniques to identify and mitigate hazards resulting from urban sprawl, industrialization, and mining activities. The most common environmental problems include surface water and groundwater contamination, dumping of hazardous wastes in unprotected ground, and air pollution related to improper waste handling.
A permanent geological storage site for reactor waste in the United States has been a limiting factor in public support for the nuclear power industry. (Nuclear weapons waste is stored in Carlsbad, New Mexico.) Requirements for geological storage include the absence of groundwater and total lack of seismic activity in a solid bedrock formation. Many locations have been proposed. In 1987, Yucca Flat, Nevada, was selected, but the selection met with almost immediate opposition because of unanswered geological questions. In March, 2009, President Barack Obama announced that plans to use Yucca Flat had been abandoned. Stephen Chu, the secretary of energy for the Obama administration, indicated that the United States might build nuclear power reactors that could utilize nuclear waste, thus dramatically lessening (but not eliminating) the amount of radioactive waste requiring permanent storage. Other countries, including Sweden, have conducted rigorous nationwide geological surveys to identify potential nuclear waste...
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Commercial Power Production from Geothermal Energy (Encyclopedia of Global Resources)
Harnessing hot springs and geysers to produce electricity has been going on at Larderello, Italy, for more than a century and is well established in Iceland and the Philippines; the latter two countries produce about 20 percent of their electricity from geothermal energy. Iceland has a geothermal capacity of 1.3 terawatt-hours per year. There are twenty-seven electricity plants at The Geysers, in Northern California, producing 750 megawatts. Important geological concerns arise when harnessing geothermal sources. The major problem at generating locations like Wairakei, New Zealand, and The Geysers is local depletion of heat sources; heated zones are tapped too intensively for too long of a period to allow recharge of heat from deep within the Earth. Other problems include the need for drilling deep wells and for fracturing rock around the deep wells at geothermal locations. Although the technology for drilling deep wells exists, it is a costly process.
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Geology (Encyclopedia of Science)
Geology is the scientific study of Earth. Geologists study the planetts formation, its internal structure, its materials, its chemical and physical processes, and its history. Mountains, valleys, plains, sea floors, minerals, rocks, fossils, and the processes that create and destroy each of these are all the domain of the geologist. Geology is divided into two broad categories of study: physical geology and historical geology.
Physical geology is concerned with the processes occurring on or below the surface of Earth and the materials on which they operate. These processes include volcanic eruptions, landslides, earthquakes, and floods. Materials include rocks, air, seawater, soils, and sediment. Physical geology further divides into more specific branches, each of which deals with its own part of Earth's materials, landforms, and processes. Mineralogy and petrology investigate the composition and origin of minerals and rocks. Volcanologists check lava, rocks, and gases on live, dormant, and extinct volcanoes. Seismologists set up instruments to monitor and predict earthquakes and volcanic eruptions.
Historical geology is concerned with the chronology of events, both physical and biological, that have taken place in Earth's history. Paleontologists study fossils (remains of ancient life) for evidence of the evolution of life on Earth. Fossils not only relate evolution, but...
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Geology (World of Earth Science)
Geology is the study of the earth. Specifically, geologists may study mountains, valleys, plains, sea floors, minerals, rocks, fossils, and the processes that create and destroy each of these. Geology consists of two broad categories of study. Physical geology studies Earth's materials (erosion, volcanism, sediment deposition, etc.) that create and destroy the materials and landforms. Historical geology explores the development of life by studying fossils (petrified remains of ancient life) and the changes in land (for example, distribution and latitude) via rocks. The two categories overlap in their coverage: for example, to examine a fossil without also examining the rock that surrounds it tells only part of the preserved organism's history.
Physical geology further divides into more specific branches, each of which deals with its own part of Earth's materials, landforms, and/or processes. Mineralogy and petrology investigate the composition and origin of minerals and rocks, respectively. Sedimentologists look at sedimentary rocks, products of the accumulation of rock fragments and other loose Earth materials, to determine how and where they formed. Volcanologists tread on live, dormant, and extinct volcanoes checking lava, rocks and gases. Seismologists set up instruments to monitor and to predict earthquakes and volcanic eruptions. Structural geologists study the ways rock layers bend and break. Plate tectonics unifies most aspects of physical geology by demonstrating how and why plates (sections of Earth's outer crust) collide and separate and how that movement influences the entire spectrum of geologic events and products.
Fossils are used in historical geology as evidence of the evolution of life on Earth. Plate tectonics adds to the story with details of the changing configuration of the continents and oceans. For years paleontologists observed that the older the rock layer, the more primitive the fossil organisms found therein, and from those observations developed evolutionary theory. Fossils not only relate evolution, but also speak of the environment in which the organism lived. Corals in rocks at the top of the Grand Canyon in Arizona, for example, show a shallow sea flooded the area around 290 million years ago. In addition, by determining the ages and types of rocks around the world, geologists piece together continental and oceanic history over the past few billions of years. For example, by matching fossil and tectonic evidence, geologists reconstructed the history and shape of the 20000 million year-old supercontinent, Pangaea.
Many other sciences also contribute to geology. The study of the chemistry of rocks, minerals, and volcanic gases is known as geochemistry. The physics of the earth is known as geophysics. Paleobotanists study fossil plants. Paleozoologists reconstruct fossil animals. Paleoclimatologists reconstruct ancient climates.
Much of current geological research focuses on resource utilization. Environmental geologists attempt to minimize human impact on Earth's resources and the impact of natural disasters on human kind. Hydrology and hydrogeology, two subdisciplines of environmental geology, deal specifically with water resources. Hydrologists study surface water whereas hydrogeologists study ground water. Both disciplines try to minimize the impact of pollution on these resources. Economic geologists focus on finding the minerals and fossil fuels (oil, natural gas, coal) needed to maintain or improve global standards of living. Extraterrestrial geology, a study in its infancy, involves surveying the materials and processes of other planets, trying to unlock the secrets of the universe and even to locate mineral deposits useful to those on Earth.
Geology (World of Forensic Science)
Geology, the study of planetary processes and histories, has applications in forensic science that date back to the 19th century fictional detective Sherlock Holmes. The principles and techniques of geology are most commonly used to identify the sources, or provenance, of rock or soil particles associated with a crime. Other applications include the use of principles borrowed from stratigraphy (the study of sequences of rocks) and structural geology (the study of deformed rocks) to infer a series of events that may be important in civil and criminal cases. Experts in the geology of specific regions can also help to identify locations using their knowledge of rock types and landforms.
Sherlock Holmes, the fictional detective created by the British author Arthur Conan Doyle (1859930), was able to distinguish different types of soils and use this information to infer the places to which suspects had traveled. The first known non-fictional use of geological techniques in a criminal investigation, however, did not occur until 1904. In that year, German chemist Georg Popp helped to identify a murder suspect by matching coal dust and particles of the mineral hornblende found on a handkerchief to the same substances at a coal processing plant and quarry that employed the suspect. Several years later, Popp matched layers of goose droppings, distinctive red sandstone fragments, and a mixture of coal, brick, and cement dust to materials at a murder victim's home, the place where the body was found, and the place where the murder weapon was found. Just as importantly, Popp determined that the suspect's shoes contained no distinctive quartz particles from field where the suspect claimed to be walking at the time of the murder. Popp's work, like the work of modern day forensic geologists, made use of the geologic concept of provenance, which is a description of the origin and history of a soil or rock particle, to place suspects in specific locations and disprove an alibi. His use of the sequence of layered goose droppings, sandstone fragments, and dust to infer the sequence in which the suspect visited those locations was an application of the principles of stratigraphy.
Geologists can often determine the geographic source and history, or provenance, of sand grains or soil particles found at a crime scene, especially if distinctive minerals or microfossils are found. This usually involves microscopic examination of soil or rock samples using magnifying glasses, reflected light microscopes, polarized transmitted light microscopes, and, in some cases, sophisticated instruments such as electron microscopes or microprobes. Even if details are not visible to the naked eye, microscopic examination can show that two seemingly similar samples of sand are composed of particles with different chemical composition, size, or shape. In some cases, the geologic details may be specific enough to place a suspect at a certain outcrop or in a specific watershed. This kind of information can be presented as evidence by geologists acting as expert witnesses in civil and criminal cases.
One of the most widely known uses of sand provenance studies in a forensic investigation involves balloons carrying explosive and incendiary bombs over the United States during World War II. Meteorological information was used to determine that the balloons were being launched in Japan and carried across the Pacific Ocean by the jet stream. The balloons carried sand-filled bags as ballast, some of which were automatically released to maintain altitude as temperature dropped each night, and the U.S. Geological Survey was asked to identify the source of the ballast sand found at balloon crash sites. The sand contained an unusual mixture of mineral grains, diatoms, and foraminifera (single celled organisms that secrete siliceous and calcareous shells), and mollusk shell pieces but no coral fragments. Government geologists studied maps and reports published before the war, and determined that sand with that unique composition existed at only two places along the Japanese coast. Those locations turned out to be very close to the actual launching points. Identification of sand grains and soil particles has been an important part of high-profile criminal cases such as the 1978 kidnapping and murder of Italian prime minister Aldo Moro and the unsuccessful attempt by Mexican federal police to cover up the 1985 kidnapping, torture, and murder of U.S. Drug Enforcement Agency operative Enrique Camarena Salazar and his pilot Alfredo Zavala Avelar.
Geologic details in images can also help investigators determine the locations in which photographs or video recordings were made. In the days after the September 11, 2001, terrorist attacks on New York City and Washington, D.C., for example, American geologists who had worked in Afghanistan were able to identify rock outcrops shown in video tapes of the terrorist leader Osama bin Laden, placing him in a certain part of that country. This use of geologic information was widely publicized and subsequent tapes were made against a cloth background in order to make identification more difficult.
SEE ALSO Forensic science; Geospatial imagery; GIS; Meteorology; Minerals; Physical evidence.