Alexander Ross Clarke: His Geodesy (1880) has remained one of the best textbooks on the subject.

geodesy, scientific discipline concerned with the precise figure of the Earth and its determination and significance. Until the advent of satellites, all geodesic work was based on land surveys made by triangulation methods employing a geodesic coordinate system (one used to study the geometry of

geoid: Earth dimensions—radius, mass, and density: …Geodesy and Geophysics adopted the Geodetic Reference System 1967, defining aequatorial, MG, and J2, o. Minor revisions to the numerical values were made in 1983. The revised values are as follows:

map: World status of mapping and basic data: Until recently the progress of geodetic triangulation, the basic survey method, was more or less limited to areas either covered by good topographic maps or scheduled for mapping. Preparations for cadastral surveys, where land partition problems abound, have occasionally led to early geodetic programs. Coastal and other surveys also require…

geoduck, (species Panopea generosa), marine invertebrate of the class Bivalvia (phylum Mollusca) that inhabits the sandy muds of the intertidal and shallow sublittoral zones of the Pacific coast of North America from southern Alaska to Baja California. The geoduck is the largest known burrowing

geoengineering, the large-scale manipulation of a specific process central to controlling Earth’s climate for the purpose of obtaining a specific benefit. Global climate is controlled by the amount of solar radiation received by Earth and also by the fate of this energy within the Earth system—that

Anjou: First dynasty of counts: Geoffrey I Grisegonelle, who succeeded Fulk II in about 960, began the policy of expansion that was to characterize this first feudal dynasty. He helped Hugh Capet to seize the French crown but died some months after the new king’s accession (987).

Geoffrey II was the count of Anjou (1040–60), whose territorial ambitions, though making him troublesome to his father, Fulk III Nerra, resulted in the further expansion of Angevin lands after his father’s death. (Geoffrey’s byname, Martel, means “the Hammer.”) In 1032 Geoffrey married Agnes, widow

Anjou: First dynasty of counts: …no sons, his two nephews, Geoffrey III the Bearded and Fulk IV le Réchin, shared the succession. However, they soon came into armed conflict, and Fulk defeated Geoffrey in 1068. Nevertheless, he had to give up most of the lands that Fulk III Nerra had acquired and to defend his…

Geoffrey IV was the count of Anjou (1131–51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry’s death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144

Geoffrey IV was the duke of Brittany and earl of Richmond, the fourth, but third surviving, son of Henry II of England and Eleanor of Aquitaine. In 1166, in furtherance of his father’s policy of extending and consolidating Angevin power in France, Geoffrey was betrothed to Constance, daughter and

Geoffrey II was the count of Anjou (1040–60), whose territorial ambitions, though making him troublesome to his father, Fulk III Nerra, resulted in the further expansion of Angevin lands after his father’s death. (Geoffrey’s byname, Martel, means “the Hammer.”) In 1032 Geoffrey married Agnes, widow

Geoffrey Of Monmouth was a medieval English chronicler and bishop of St. Asaph (1152), whose major work, the Historia regum Britanniae (History of the Kings of Britain), brought the figure of Arthur into European literature. In three passages of the Historia Geoffrey describes himself as “Galfridus

Geoffrey IV was the duke of Brittany and earl of Richmond, the fourth, but third surviving, son of Henry II of England and Eleanor of Aquitaine. In 1166, in furtherance of his father’s policy of extending and consolidating Angevin power in France, Geoffrey was betrothed to Constance, daughter and

Geoffrey IV was the count of Anjou (1131–51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry’s death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144

Geoffrey IV was the count of Anjou (1131–51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry’s death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144

Marie-Thérèse Rodet Geoffrin was a French hostess whose salon in the Hôtel de Rambouillet was an international meeting place of artists and men of letters from 1749 to 1777. The daughter of a valet, she married a rich manufacturer, a member of the newly influential bourgeoisie, with whom she had no

Geoffrey of Villehardouin was a French soldier, chronicler, marshal of Champagne, and one of the leaders of the Fourth Crusade (1201–04), which he described in his Conquest of Constantinople. He was the first serious writer of an original prose history in Old French. Although he was only one of the

Geoffrey IV was the count of Anjou (1131–51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry’s death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144

Geoffrey II was the count of Anjou (1040–60), whose territorial ambitions, though making him troublesome to his father, Fulk III Nerra, resulted in the further expansion of Angevin lands after his father’s death. (Geoffrey’s byname, Martel, means “the Hammer.”) In 1032 Geoffrey married Agnes, widow

Geoffrey IV was the count of Anjou (1131–51), Maine, and Touraine and ancestor of the Plantagenet kings of England through his marriage, in June 1128, to Matilda (q.v.), daughter of Henry I of England. On Henry’s death (1135), Geoffrey claimed the duchy of Normandy; he finally conquered it in 1144

Geoffrey IV was the duke of Brittany and earl of Richmond, the fourth, but third surviving, son of Henry II of England and Eleanor of Aquitaine. In 1166, in furtherance of his father’s policy of extending and consolidating Angevin power in France, Geoffrey was betrothed to Constance, daughter and

Étienne-François Geoffroy was a French chemist, the first chemist to speak of affinity in terms of fixed attractions between different bodies. Assuming that one acid displaces another acid of weaker affinity for a specific base in the salt of that base, Geoffroy composed tables (1718) listing the

Étienne Geoffroy Saint-Hilaire was a French naturalist who established the principle of “unity of composition,” postulating a single consistent structural plan basic to all animals as a major tenet of comparative anatomy, and who founded teratology, the study of animal malformation. After taking a

Isidore Geoffroy Saint-Hilaire was a French zoologist noted for his work on anatomical abnormalities in humans and lower animals. In 1824 Geoffroy joined his father at the National Museum of Natural History as an assistant naturalist, and, after taking his M.D. in 1829, he taught zoology from 1830

Étienne-François Geoffroy was a French chemist, the first chemist to speak of affinity in terms of fixed attractions between different bodies. Assuming that one acid displaces another acid of weaker affinity for a specific base in the salt of that base, Geoffroy composed tables (1718) listing the

Geoffroy’s cat, (Oncifelis geoffroyi), South American cat of the family Felidae, found in mountainous regions, especially in Argentina. It is gray or brown with black markings and grows to a length of about 90 cm (36 inches), including a tail of about 40 cm (16 inches). Geoffroy’s cat climbs well

Étienne-François Geoffroy was a French chemist, the first chemist to speak of affinity in terms of fixed attractions between different bodies. Assuming that one acid displaces another acid of weaker affinity for a specific base in the salt of that base, Geoffroy composed tables (1718) listing the

Ascomycota: Earth tongue is the common name for the more than 80 Geoglossum species of the order Helotiales. They produce black to brown, club-shaped fruiting structures on soil or on decaying wood.

Abraham Gottlob Werner: …a subject that he called geognosy. Influenced by the works of Johann Gottlob Lehmann and Georg Christian Füchsel, Werner demonstrated that the rocks of the Earth are deposited in a definite order. Although he had never travelled, he assumed that the sequence of the rocks he observed in Saxony was…

Bernhardus Varenius: Geographia generalis (1650), Varenius’s best-known work, sought to lay down the general principles of geography on a wide scientific basis according to the knowledge of the day. It not only was a systematic geography on a scale not previously attempted but also contained a scheme…

geomorphic cycle, theory of the evolution of landforms. In this theory, first set forth by William M. Davis between 1884 and 1934, landforms were assumed to change through time from “youth” to “maturity” to “old age,” each stage having specific characteristics. The initial, or youthful, stage of

dialect: Geographic dialects: The most widespread type of dialectal differentiation is regional, or geographic. As a rule, the speech of one locality differs at least slightly from that of any other place. Differences between neighbouring local dialects are usually small, but, in traveling farther in the…

GIS, computer system for performing geographical analysis. GIS has four interactive components: an input subsystem for converting into digital form (digitizing) maps and other spatial data; a storage and retrieval subsystem; an analysis subsystem; and an output subsystem for producing maps, tables,

military intelligence: Geographic: Gained from studying natural characteristics including terrain, climate, natural resources, transportation, boundaries, and population distribution, military geographic intelligence involves evaluating all such factors that in any way influence military operations.

latitude and longitude: Technical considerations: Geographic latitude, which is the kind used in mapping, is calculated using a slightly different process. Because Earth is not a perfect sphere—the planet’s curvature is flatter at the poles—geographic latitude is the arc resulting from an angle created by the equatorial plane and the…

geographic mosaic theory of coevolution, in ecology, the theory postulating that the long-term dynamics of coevolution may occur over large geographic ranges rather than within local populations. It is based on the observation that a species may adapt and become specialized to another species

Board on Geographic Names (BGN), interdepartmental agency of the U.S. government created in 1890 and providing standardized geographic names of foreign and domestic places for use by the federal government. It was established in its present form by a public law enacted in 1947. Located in

North Pole, the northern end of Earth’s axis, lying in the Arctic Ocean, about 450 miles (725 km) north of Greenland. This geographic North Pole does not coincide with the magnetic North Pole—to which magnetic compasses point and which in the early 21st century lay north of the Queen Elizabeth

geographic range, in ecology, the collective area in which all members of a particular species are found during their lifetime. The term geographic range has often referred to the natural extent of a species’ distribution; however, it also includes areas where a species was introduced by human

lighthouse: Geographic range and luminous range: This is known as the geographic range of the light. (One nautical mile, the distance on Earth’s surface traversed by one minute of arc latitude, is equivalent to 1.15 statute miles or 1.85 km.)

evolution: Geographic speciation: One common mode of speciation is known as geographic, or allopatric (in separate territories), speciation. The general model of the speciation process advanced in the previous section applies well to geographic speciation. The first stage begins as a result of geographic separation between…

glossitis: Geographic tongue (benign migratory glossitis) refers to the chronic presence of irregularly shaped, bright red areas on the tongue, surrounded by a narrow white zone; normal tongue epithelium may grow back in one area while new areas of glossitis develop elsewhere, making the disease seem…

zenith: …it would point to the geographic zenith. Because the Earth rotates and is not a perfect sphere, the geocentric zenith is slightly different from the geographic zenith except at the Equator and the poles. Geocentric zenith is the intersection with the celestial sphere of a straight line drawn through the…

museum: South America: …Lima, Peru (1891), or the Geographical and Geological Museum at São Paulo, Brazil (1895). Others were created by provincial bodies: the regional museums at Córdoba (1887) and Gualeguaychu (1898), both in Argentina, and at Ouro Prêto, Brazil (1876); the Hualpen Museum in Chile (1882); and the Municipal Museum and Library…

geography: The development of academic geography in the United Kingdom: …in 1893 that founded the Geographical Association, which aimed to be a society for teachers of geography at all levels and became a successful lobby for the discipline.

Equator, great circle around Earth that is everywhere equidistant from the geographic poles and lies in a plane perpendicular to Earth’s axis. This geographic, or terrestrial, Equator divides Earth into the Northern and Southern hemispheres and forms the imaginary reference line on Earth’s surface

Halford Mackinder: …Geographical Society in 1904, “The Geographical Pivot of History.” In it he argued that interior Asia and eastern Europe (the heartland) had become the strategic centre of the “World Island” as a result of the relative decline of sea power as against land power and of the economic and industrial…

Géographie Universelle, major French work on regional geography of the entire world. It consists of 15 volumes in 23 parts. The work is known for its vivid characterization and description of each region. The first French attempt to provide a universal geography was Conrad Malte-Brun’s Précis de la

map: Greek maps and geography: His monumental work, the Guide to Geography (Geōgraphikē hyphēgēsis), was produced in eight volumes. The first volume discussed basic principles and dealt with map projection and globe construction. The next six volumes carried a list of the names of some 8,000 places and their approximate latitudes and longitudes. Except…

Alfred Hettner: …of geography was the influential Geographische Zeitung (“Geographical Journal”), first published in 1899. The first volume of his Grundzüge der Länderkunde (1907; “Foundations of Regional Geography”) dealt with Europe, but its companion volume, on other regions, did not appear until 1924. He also wrote Vergleichende Länderkunde, 4 vol. (1933–35; “Comparative…

Geographos, an Apollo asteroid (one that passes inside Earth’s orbit). Geographos was discovered on September 14, 1951, by American astronomers Albert Wilson and Rudolf Minkowski at the Palomar Observatory. Geographos revolves around the Sun once in 1.39 Earth years in an eccentric moderately

al-Khwārizmī: …of the Earth”; translated as Geography), which presented the coordinates of localities in the known world based, ultimately, on those in the Geography of Ptolemy (flourished 127–145 ce) but with improved values for the length of the Mediterranean Sea and the location of cities in Asia and Africa. He also…

Strabo: …Greek geographer and historian whose Geography is the only extant work covering the whole range of peoples and countries known to both Greeks and Romans during the reign of Augustus (27 bce–14 ce). Its numerous quotations from technical literature, moreover, provide a remarkable account of the state of Greek geographical…

geography, the study of the diverse environments, places, and spaces of Earth’s surface and their interactions. It seeks to answer the questions of why things are as they are, where they are. The modern academic discipline of geography is rooted in ancient practice, concerned with the

map: Revival of Ptolemy: …old Greek manuscripts, including Ptolemy’s Geography, from destruction. The rediscovery of this great work came at a fortunate time because the recent development of a printing industry capable of handling map reproduction made possible its circulation far beyond the few scholars who otherwise would have enjoyed access to it. This,…

Elizabeth Bishop: Questions of Travel, Geography III, and The Complete Poems: Questions of Travel (1965) and Geography III (1976) offer spare, powerful meditations on the need for self-exploration, on the value of art (especially poetry) in human life, and on human responsibility in a chaotic world. The latter collection includes some of Bishop’s best-known poems, among them “In the Waiting Room,”…

Jedidiah Morse: …published in the United States, Geography Made Easy (1784). His geographical writings dominated the field in the United States until his death.

Sam Shepard: …of Crime (produced 1972) and Geography of a Horse Dreamer (produced 1974)—premiered in London. In late 1974 he became playwright-in-residence at the Magic Theatre in San Francisco, where most of his plays over the next decade were first produced.

Alfredo Jaar: Geography=War (1990) utilized proportionately accurate maps of the world (in which North America is much smaller than on traditional maps) to force viewers to confront their assumptions about geography and power. These maps illustrated the journey taken by toxic waste sent to Koko, Nigeria, by…

geoid, model of the figure of Earth—i.e., of the planet’s size and shape—that coincides with mean sea level over the oceans and continues in continental areas as an imaginary sea-level surface defined by spirit level. It serves as a reference surface that can be used to measure precise elevations

dating: Geologic column and its associated time scale: The end product of correlation is a mental abstraction called the geologic column. It is the result of integrating all the world’s individual rock sequences into a single sequence. In order to communicate the fine structure of this…

geology: …rocks, thereby completing a full cycle of the transfer of matter from an old continent to a young ocean and ultimately to the formation of new sedimentary rocks. Knowledge of the processes of interaction of the atmosphere and the hydrosphere with the surface rocks and soils of the Earth’s crust…

nuclear reactor: Geologic disposal: …nuclear power plants is called geologic disposal. This means that all conditioned nuclear wastes are to be deposited in mined cavities deep underground. Shafts are to be sunk into a solid rock stratum, with tunnel corridors extending horizontally from the central shaft region and tunnel “rooms” laterally from the corridors.…

geochronology: Early attempts at mapping and correlation: …one of the first large-scale geologic maps of a region is its essential accuracy in portraying what is now known to be the geologic succession for the particular area of Britain covered.

Earth sciences: William Smith and faunal succession: …when William Smith published his Geologic Map of England and Wales with Part of Scotland (1815). A self-educated surveyor and engineer, Smith had the habit of collecting fossils and making careful note of the strata that contained them. He discovered that the different stratified formations in England contain distinctive assemblages…

marine geology, scientific discipline that is concerned with all geological aspects of the continental shelves and slopes and the ocean basins. In practice, the principal focus of marine geology has been on marine sedimentation and on the interpretation of the many bottom samples that have been

dating: Multiple ages for a single rock: the thermal effect: These are called geologic provinces. By contrast, rocks that have approached their melting point—say, 750 °C (1,382 °F), which can cause new zircon growth during a second thermal event—are rare, and those that have done this more than once are almost nonexistent.

geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day. Modern geologic time scales additionally often include the Hadean Eon, which

dike, in geology, tabular or sheetlike igneous body that is often oriented vertically or steeply inclined to the bedding of preexisting intruded rocks; similar bodies oriented parallel to the bedding of the enclosing rocks are called sills. A dike set is composed of several parallel dikes; when the

engineering geology, the scientific discipline concerned with the application of geological knowledge to engineering problems—e.g., to reservoir design and location, determination of slope stability for construction purposes, and determination of earthquake, flood, or subsidence danger in areas

Richard Kirwan: …books on chemistry, Kirwan wrote Geological Essays (1799), a controversial response to the pioneering work of geologist James Hutton; a work on comparative climatology; a two-volume work on logic; and a volume of essays on metaphysics.

undersea exploration: Exploration of the seafloor and the Earth’s crust: …those that employ Seabeam and Gloria (Geological Long-Range Inclined Asdic) permit mapping two-dimensional swaths with great accuracy from a single ship. These methods are widely used to ascertain the major features of the seafloor. The Gloria system, for example, can produce a picture of the morphology of a region at…

museum: South America: …in the case of the Geological Museum in Lima, Peru (1891), or the Geographical and Geological Museum at São Paulo, Brazil (1895). Others were created by provincial bodies: the regional museums at Córdoba (1887) and Gualeguaychu (1898), both in Argentina, and at Ouro Prêto, Brazil (1876); the Hualpen Museum in…

marine geology, scientific discipline that is concerned with all geological aspects of the continental shelves and slopes and the ocean basins. In practice, the principal focus of marine geology has been on marine sedimentation and on the interpretation of the many bottom samples that have been

dating: Analysis of separated minerals: …mineral is widespread in the geologic record, it is more valuable for dating as more units can be measured for age and compared by the same method. However, if a single parent-daughter pair that is amenable to precise analysis can be measured in a variety of minerals, the ages of…

geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy. An introduction to the geochemical and geophysical sciences logically begins with mineralogy, because Earth’s rocks are composed of minerals—inorganic elements or

geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy. An introduction to the geochemical and geophysical sciences logically begins with mineralogy, because Earth’s rocks are composed of minerals—inorganic elements or

Arthur L. Day: …and president (1938) of the Geological Society of America, which created the Arthur L. Day Award in his honour.

Sir William Edmond Logan: In 1842, when the Geological Survey of Canada was formed, Logan was made its director, and he served in this capacity until 1869. His chief work for the Geological Survey was his monumental Report on the Geology of Canada (1863), a compilation of 20 years of research. Another of…

Sir Henry Thomas De La Beche: …a geologist who founded the Geological Survey of Great Britain, which made the first methodical geologic survey of an entire country ever undertaken.

Rocky Mountains: Study and exploration: …surveys were organized by the U.S. government following the American Civil War: the survey of the 40th parallel led by Clarence King (1867–78), the geologic survey of Nebraska and Wyoming led by Ferdinand Hayden (1867–78), the 100th-meridian survey led by George Wheeler (1872–79), and the expeditions to the Green and…

geology: Isotopic geochemistry: …used as a form of geologic thermometer. The ratio of oxygen-16 to oxygen-18 in calcium carbonate secreted by various marine organisms from calcium carbonate in solution in seawater is influenced by the temperature of the seawater. Precise measurement of the proportions of oxygen-16 with respect to oxygen-18 in calcareous shells…

geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day. Modern geologic time scales additionally often include the Hadean Eon, which

geology, the fields of study concerned with the solid Earth. Included are sciences such as mineralogy, geodesy, and stratigraphy. An introduction to the geochemical and geophysical sciences logically begins with mineralogy, because Earth’s rocks are composed of minerals—inorganic elements or

James Hall: …culminated in his massive report Geology of New York (part 4, 1843), a classic in American geology. Although he could not explain the uplift of the sedimentary beds that formed the Appalachians, his observations were instrumental in forming the geosynclinal theory.

George Ferdinand Becker: …report from this work is Geology of the Comstock Lode and Washoe District (1882).

Joseph Barrell: …he presented his ideas in Geology of the Marysville Mining District, Montana (1907). In this classic work on geology he proposed the then new concept that molten magma from the Earth’s interior infiltrated fissures in the crust and created intrusions, lavas, and metamorphism.

wolf spider: Major genera and species: ” Burrowing wolf spiders (Geolycosa), which spend most of their lives in burrows, have heavy front legs that are used for digging.

paleogeography: Linear magnetic anomalies: Earth’s magnetic field has another important property. Like the Sun’s magnetic field, Earth’s magnetic field periodically “flips,” or reverses polarity—that is, the North and South poles switch places. Fluctuations, or anomalies in the intensity of the magnetic field, occur at the boundaries between…

dynamo theory, geophysical theory that explains the origin of Earth’s main magnetic field in terms of a self-exciting (or self-sustaining) dynamo. In this dynamo mechanism, fluid motion in Earth’s outer core moves conducting material (liquid iron) across an already existing weak magnetic field and

geomagnetic field, magnetic field associated with Earth. It is primarily dipolar (i.e., it has two poles, the geomagnetic North and South poles) on Earth’s surface. Away from the surface the dipole becomes distorted. In the 1830s the German mathematician and astronomer Carl Friedrich Gauss studied

North Pole: …steadily migrating northwest)—or with the geomagnetic North Pole, the northern end of Earth’s geomagnetic field (about 79°30′ N 71°30′ W). The geographic pole, located at a point where the ocean depth is about 13,400 feet (4,080 metres) deep and covered with drifting pack ice, experiences six months of complete sunlight…

geomagnetic reversal, an alternation of the Earth’s magnetic polarity in geologic time. See polar

geomagnetic field: Dipolar field: …hemispheres not far from the geomagnetic poles. The weakest field occurred along the magnetic equator, with the lowest value being observed on the Atlantic coast of South America.

geomagnetic reversal, an alternation of the Earth’s magnetic polarity in geologic time. See polar

South Pole: …it coincide with the geomagnetic South Pole, the southern end of the Earth’s geomagnetic field (this pole also moves; during the early 1990s it was located about 79°13′ S, 108°44′ E). The geographic pole, at an elevation of some 9,300 feet (2,830 metres; the elevation also changes constantly) above sea…

geomagnetic storm, disturbance of Earth’s upper atmosphere brought on by coronal mass ejections—i.e., large eruptions from the Sun’s outer atmosphere, or corona. The material associated with these eruptions consists primarily of protons and electrons with an energy of a few thousand electron volts.

geomagnetic storm of 1859, largest geomagnetic storm ever recorded. The storm, which occurred on Sept. 2, 1859, produced intense auroral displays as far south as the tropics. It also caused fires as the enhanced electric current flowing through telegraph wires ignited recording tape at telegraph

geomagnetic field: Magnetospheric substorms—unbalanced flux transfer: Magnetospheric substorm is the name applied to the collection of processes that occur throughout the magnetosphere at the time of an auroral and magnetic disturbance. The term substorm was originally used to signify that the processes produce an event, localized in…