Portal:Geophysics
Portal maintenance status: (November 2018)
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Introduction
Geophysics /dʒiːoʊfɪzɪks/ is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. However, modern geophysics organizations use a broader definition that includes the water cycle including snow and ice; fluid dynamics of the oceans and the atmosphere; electricity and magnetism in the ionosphere and magnetosphere and solar-terrestrial relations; and analogous problems associated with the Moon and other planets.
Although geophysics was only recognized as a separate discipline in the 19th century, its origins date back to ancient times. The first magnetic compasses were made from lodestones, while more modern magnetic compasses played an important role in the history of navigation. The first seismic instrument was built in 132 AD. Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox; and instruments were developed to measure the Earth's shape, density and gravity field, as well as the components of the water cycle. In the 20th century, geophysical methods were developed for remote exploration of the solid Earth and the ocean, and geophysics played an essential role in the development of the theory of plate tectonics.
Selected general articles
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In particular, it can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 25,772 years. This is similar to the precession of a spinning-top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis—nutation and polar motion—are much smaller in magnitude.
Earth's precession was historically called the precession of the equinoxes, because the equinoxes moved westward along the ecliptic relative to the fixed stars, opposite to the yearly motion of the Sun along the ecliptic. This term is still used in non-technical discussions, that is, when detailed mathematics are absent. Historically,
the discovery of the precession of the equinoxes is usually attributed in the west to the Hellenistic-era (second-century BCE) astronomer Hipparchus, although there are claims of its earlier discovery, such as in the Indian text, Vedanga Jyotisha, dating from 700 BC.
With improvements in the ability to calculate the gravitational force between planets during the first half of the nineteenth century, it was recognized that the ecliptic itself moved slightly, which was named planetary precession, as early as 1863, while the dominant component was named lunisolar precession. Their combination was named general precession, instead of precession of the equinoxes. Read more...
Earth's gravity measured by NASA GRACE mission, showing deviations from the theoretical gravity of an idealized smooth Earth, the so-called Earth ellipsoid. Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker. (Animated version.)
The gravity of Earth, denoted by g, is the net acceleration that is imparted to objects due to the combined effect of gravitation (from distribution of mass within Earth) and the centrifugal force (from the Earth's rotation).
In SI units this acceleration is measured in metres per second squared (in symbols, m/s2 or m·s−2) or equivalently in newtons per kilogram (N/kg or N·kg−1). Near Earth's surface, gravitational acceleration is approximately 9.8 m/s2, which means that, ignoring the effects of air resistance, the speed of an object falling freely will increase by about 9.8 metres per second every second. This quantity is sometimes referred to informally as little g (in contrast, the gravitational constant G is referred to as big G). Read more...
Illustration of the dynamo mechanism that creates the Earth's magnetic field: convection currents of fluid metal in the Earth's outer core, driven by heat flow from the inner core, organized into rolls by the Coriolis force, create circulating electric currents, which generate the magnetic field.
In physics, the dynamo theory proposes a mechanism by which a celestial body such as Earth or a star generates a magnetic field. The dynamo theory describes the process through which a rotating, convecting, and electrically conducting fluid can maintain a magnetic field over astronomical time scales. A dynamo is thought to be the source of the Earth's magnetic field and the magnetic fields of other planets. Read more...
Computer simulation of the Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core.
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss). Approximately, it is the field of a magnetic dipole currently tilted at an angle of about 11 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. The North geomagnetic pole, located near Greenland in the northern hemisphere, is actually the south pole of the Earth's magnetic field, and the South geomagnetic pole is the north pole. The magnetic field is generated by electric currents due to the motion of convection currents of molten iron in the Earth's outer core driven by heat escaping from the core, a natural process called a geodynamo.
While the North and South magnetic poles are usually located near the geographic poles, they can wander widely over geological time scales, but sufficiently slowly for ordinary compasses to remain useful for navigation. However, at irregular intervals averaging several hundred thousand years, the Earth's field reverses and the North and South Magnetic Poles relatively abruptly switch places. These reversals of the geomagnetic poles leave a record in rocks that are of value to paleomagnetists in calculating geomagnetic fields in the past. Such information in turn is helpful in studying the motions of continents and ocean floors in the process of plate tectonics. Read more...
Model forecast of Hurricane Mitch created by the Geophysical Fluid Dynamics Laboratory. The arrows are wind vectors and the grey shading indicates an equivalent potential temperature surface that highlights the surface inflow layer and eyewall region.
Geophysical fluid dynamics, in its broadest meaning, refers to the fluid dynamics of naturally occurring flows, such as lava flows, oceans, and planetary atmospheres, on Earth and other planets.
Two physical features that are common to many of the phenomena studied in geophysical fluid dynamics are rotation of the fluid due to the planetary rotation and stratification (layering). The applications of geophysical fluid dynamics do not generally include the circulation of the mantle, which is the subject of geodynamics, or fluid phenomena in the magnetosphere. Read more...- Mineral physics is the science of materials that compose the interior of planets, particularly the Earth. It overlaps with petrophysics, which focuses on whole-rock properties. It provides information that allows interpretation of surface measurements of seismic waves, gravity anomalies, geomagnetic fields and electromagnetic fields in terms of properties in the deep interior of the Earth. This information can be used to provide insights into plate tectonics, mantle convection, the geodynamo and related phenomena.
Laboratory work in mineral physics require high pressure measurements. The most common tool is a diamond anvil cell, which uses diamonds to put a small sample under pressure that can approach the conditions in the Earth's interior. Read more...
Mantle convection is the slow creeping motion of Earth's solid silicate mantle caused by convection currents carrying heat from the interior to the planet's surface. The Earth's surface lithosphere, which rides atop the asthenosphere (the two components of the upper mantle), is divided into a number of plates that are continuously being created and consumed at their opposite plate boundaries. Accretion occurs as mantle is added to the growing edges of a plate, associated with seafloor spreading. This hot added material cools down by conduction and convection of heat. At the consumption edges of the plate, the material has thermally contracted to become dense, and it sinks under its own weight in the process of subduction usually at an ocean trench.
This subducted material sinks through the Earth's interior. Some subducted material appears to reach the lower mantle, while in other regions, this material is impeded from sinking further, possibly due to a phase transition from spinel to silicate perovskite and magnesiowustite, an endothermic reaction. Read more...- Mathematical geophysics is concerned with developing mathematical methods for use in geophysics. As such, it has application in many fields in geophysics, particularly geodynamics and seismology. Read more...
- Tectonophysics, a branch of geophysics, is the study of the physical processes that underlie tectonic deformation. The field encompasses the spatial patterns of stress, strain, and differing rheologies in the lithosphere and asthenosphere of the Earth; and the relationships between these patterns and the observed patterns of deformation due to plate tectonics. Read more...
Seismology ( /saɪzˈmɒlədʒi/; from Ancient Greek σεισμός (seismós) meaning "earthquake" and -λογία (-logía) meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other planet-like bodies. The field also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic, atmospheric, and artificial processes such as explosions. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of earth motion as a function of time is called a seismogram. A seismologist is a scientist who does research in seismology. Read more...
Zhang Heng, inventor of the first seismoscope.
This is a list of geophysicists, people who made notable contributions to geophysics, whether or not geophysics was their primary field. These include historical figures who laid the foundations for the field of geophysics. More recently, some of the top awards for geophysicists are the Vetlesen Prize (intended to be the equivalent of a Nobel Prize for geology or geophysics); the William Bowie Medal (the top award of the American Geophysical Union); and the Crafoord Prize for geosciences. Some geophysicists have also won more general prizes such as the Nobel Prize and the Kyoto Prize. Read more...- Geophysical survey is the systematic collection of geophysical data for spatial studies. Detection and analysis of the geophysical signals forms the core of Geophysical signal processing. The magnetic and gravitational fields emanating from the Earth's interior hold essential information concerning seismic activities and the internal structure. Hence, detection and analysis of the electric and Magnetic fields is very crucial. As the Electromagnetic and gravitational waves are multi-dimensional signals, all the 1-D transformation techniques can be extended for the analysis of these signals as well. Hence this article also discusses multi-dimensional signal processing techniques.
Geophysical surveys may use a great variety of sensing instruments, and data may be collected from above or below the Earth's surface or from aerial, orbital, or marine platforms. Geophysical surveys have many applications in geology, archaeology, mineral and energy exploration, oceanography, and engineering. Geophysical surveys are used in industry as well as for academic research. Read more...
Automatic ground penetrating Radar (upGPR) near Swiss Camp (Greenland)
Near-surface geophysics is the use of geophysical methods to investigate small-scale features in the shallow (tens of meters) subsurface. It is closely related to applied geophysics or exploration geophysics. Methods used include seismic refraction and reflection, gravity, magnetic, electric, and electromagnetic methods. Many of these methods were developed for oil and mineral exploration but are now used for a great variety of applications, including archaeology, environmental science, forensic science, military intelligence, geotechnical investigation, treasure hunting, and hydrogeology. In addition to the practical applications, near-surface geophysics includes the study of biogeochemical cycles. Read more...
Seismic velocities and boundaries in the interior of the Earth sampled by seismic waves.
The following outline is provided as an overview of and topical guide to geophysics:
Geophysics – the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and composition; its dynamics and their surface expression in plate tectonics, the generation of magmas, volcanism and rock formation. However, modern geophysics organizations have a broader definition that includes the hydrological cycle including snow and ice; fluid dynamics of the oceans and the atmosphere; electricity and magnetism in the ionosphere and magnetosphere and solar-terrestrial relations; and analogous problems associated with the Moon and other planets. Read more...
Magnetic stripes are the result of reversals of the Earth's field and seafloor spreading. New oceanic crust is magnetized as it forms and then it moves away from the ridge in both directions. The models show a ridge (a) about 5 million years ago (b) about 2 to 3 million years ago and (c) in the present.
This term is also sometimes used for natural remanent magnetization.
Paleomagnetism (or palaeomagnetism in the United Kingdom) is the study of the record of the Earth's magnetic field in rocks, sediment, or archeological materials. Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form. This record provides information on the past behavior of Earth's magnetic field and the past location of tectonic plates. The record of geomagnetic reversals preserved in volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-scale that is used as a geochronologic tool. Geophysicists who specialize in paleomagnetism are called paleomagnetists. Read more...
Seismic waves are waves of energy that travel through the Earth's layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy. Many other natural and anthropogenic sources create low-amplitude waves commonly referred to as ambient vibrations. Seismic waves are studied by geophysicists called seismologists. Seismic wave fields are recorded by a seismometer, hydrophone (in water), or accelerometer.
The propagation velocity of the waves depends on density and elasticity of the medium.Velocity tends to increase with depth and ranges from approximately 2 to 8 km/s in the Earth's crust, up to 13 km/s in the deep mantle. Read more...
Temperature profile of the inner Earth, schematic view (estimated).
Geothermal gradient is the rate of increasing temperature with respect to increasing depth in the Earth's interior. Away from tectonic plate boundaries, it is about 25–30 °C/km (72-87 °F/mi) of depth near the surface in most of the world. Strictly speaking, geo-thermal necessarily refers to the Earth but the concept may be applied to other planets.
The Earth's internal heat comes from a combination of residual heat from planetary accretion, heat produced through radioactive decay, latent heat from core crystallization, and possibly heat from other sources. The major heat-producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-232. At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa (3.6 million atm). Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. Heat production was twice that of present-day at approximately 3 billion years ago, resulting in larger temperature gradients within the Earth, larger rates of mantle convection and plate tectonics, allowing the production of igneous rocks such as komatiites that are no longer formed. Read more...
Computer simulation of the Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core.
Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from the Earth's interior out into space, where it meets the solar wind, a stream of charged particles emanating from the Sun. Its magnitude at the Earth's surface ranges from 25 to 65 microteslas (0.25 to 0.65 gauss). Approximately, it is the field of a magnetic dipole currently tilted at an angle of about 11 degrees with respect to Earth's rotational axis, as if there were a bar magnet placed at that angle at the center of the Earth. The North geomagnetic pole, located near Greenland in the northern hemisphere, is actually the south pole of the Earth's magnetic field, and the South geomagnetic pole is the north pole. The magnetic field is generated by electric currents due to the motion of convection currents of molten iron in the Earth's outer core driven by heat escaping from the core, a natural process called a geodynamo.
While the North and South magnetic poles are usually located near the geographic poles, they can wander widely over geological time scales, but sufficiently slowly for ordinary compasses to remain useful for navigation. However, at irregular intervals averaging several hundred thousand years, the Earth's field reverses and the North and South Magnetic Poles relatively abruptly switch places. These reversals of the geomagnetic poles leave a record in rocks that are of value to paleomagnetists in calculating geomagnetic fields in the past. Such information in turn is helpful in studying the motions of continents and ocean floors in the process of plate tectonics. Read more...
In the inertial frame of reference (upper part of the picture), the black ball moves in a straight line. However, the observer (brown dot) who is standing in the rotating/non-inertial frame of reference (lower part of the picture) sees the object as following a curved path due to the Coriolis and centrifugal forces present in this frame.
In physics, the Coriolis force is an inertial force that seems to act on objects that are in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the left of the motion of the object. In one with anticlockwise (or counterclockwise) rotation, the force acts to the right. Deflection of an object due to the Coriolis force is called the Coriolis effect. Though recognized previously by others, the mathematical expression for the Coriolis force appeared in an 1835 paper by French scientist Gaspard-Gustave de Coriolis, in connection with the theory of water wheels. Early in the 20th century, the term Coriolis force began to be used in connection with meteorology.
Newton's laws of motion describe the motion of an object in an inertial (non-accelerating) frame of reference. When Newton's laws are transformed to a rotating frame of reference, the Coriolis force and centrifugal force appear. Both forces are proportional to the mass of the object. The Coriolis force is proportional to the rotation rate and the centrifugal force is proportional to the square of the rotation rate. The Coriolis force acts in a direction perpendicular to the rotation axis and to the velocity of the body in the rotating frame and is proportional to the object's speed in the rotating frame (more precisely, to the component of its velocity that is perpendicular to the axis of rotation). The centrifugal force acts outwards in the radial direction and is proportional to the distance of the body from the axis of the rotating frame. These additional forces are termed inertial forces, fictitious forces or pseudo forces. They allow the application of Newton's laws to a rotating system. They are correction factors that do not exist in a non-accelerating or inertial reference frame. Read more...
Geodesy (/dʒiːˈɒdɪsi/),[full citation needed] also known as geodetics, is the earth science of accurately measuring and understanding three of Earth's fundamental properties: its geometric shape, orientation in space, and gravitational field. The field also incorporates studies of how these properties change over time and equivalent measurements for other planets (known as planetary geodesy). Geodynamical phenomena include crustal motion, tides, and polar motion, which can be studied by designing global and national control networks, applying space and terrestrial techniques, and relying on datums and coordinate systems. Read more...- Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It applies physics, chemistry and mathematics to the understanding of how mantle convection leads to plate tectonics and geologic phenomena such as seafloor spreading, mountain building, volcanoes, earthquakes, faulting and so on. It also attempts to probe the internal activity by measuring magnetic fields, gravity, and seismic waves, as well as the mineralogy of rocks and their isotopic composition. Methods of geodynamics are also applied to exploration of other planets. Read more...
- The Chandler wobble or variation of latitude is a small deviation in the Earth's axis of rotation relative to the solid earth, which was discovered by American astronomer Seth Carlo Chandler in 1891. It amounts to change of about 9 metres (30 ft) in the point at which the axis intersects the Earth's surface and has a period of 433 days. This wobble, which is a nutation, combines with another wobble with a period of one year, so that the total polar motion varies with a period of about 7 years.
The Chandler wobble is an example of the kind of motion that can occur for a spinning object that is not a sphere; this is called a free nutation. Somewhat confusingly, the direction of the Earth's spin axis relative to the stars also varies with different periods, and these motions—caused by the tidal forces of the Moon and Sun—are also called nutations, except for the slowest, which are precessions of the equinoxes. Read more...
Schematic of the lunar portion of Earth's tides, showing (exaggerated) high tides at the sublunar point and its antipode for the hypothetical case of an ocean of constant depth without land. There would also be smaller, superimposed bulges on the sides facing toward and away from the sun.
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun, and the rotation of Earth.
Tide tables can be used to find the predicted times and amplitude (or "tidal range") of tides at any given locale. The predictions are influenced by many factors including the alignment of the Sun and Moon, the phase and amplitude of the tide (pattern of tides in the deep ocean), the amphidromic systems of the oceans, and the shape of the coastline and near-shore bathymetry (see Timing). They are however only predictions, the actual time and height of the tide is affected by wind and atmospheric pressure. Some shorelines experience a semi-diurnal tide—two nearly equal high and low tides each day. Other locations experience a diurnal tide—only one high and low tide each day. A "mixed tide"—two uneven tides a day, or one high and one low—is also possible. Read more...
Selected geophysicts
- Drummond Hoyle Matthews FRS (5 February 1931 – 20 July 1997), known as "Drum", was a British marine geologist and geophysicist and a key contributor to the theory of plate tectonics. His work, along with that of fellow Briton Fred Vine and Canadian Lawrence Morley, showed how variations in the magnetic properties of rocks forming the ocean floor could be consistent with, and ultimately help confirm, Harry Hammond Hess's 1962 theory of seafloor spreading. In 1989 he was awarded the Geological Society of London's highest honour, the Wollaston Medal. Read more...
David John Stevenson (born September 2, 1948) is a professor of planetary science at Caltech. Originally from New Zealand, he received his Ph.D. from Cornell University in physics, where he proposed a model for the interior of Jupiter. He is well known for applying fluid mechanics and magnetohydrodynamics to understand the internal structure and evolution of planets and moons. In 1984, he received the H. C. Urey Prize awarded by the Division for Planetary Sciences of the American Astronomical Society. He is a fellow of the Royal Society and a member of the United States National Academy of Sciences.[citation needed] Read more...
Felix Andries Vening Meinesz (30 July 1887 in The Hague – 10 August 1966 in Amersfoort) was a Dutch geophysicist and geodesist. He is known for his invention of a precise method for measuring gravity. Thanks to his invention, it became possible to measure gravity at sea, which led him to the discovery of gravity anomalies above the ocean floor. He later attributed these anomalies to continental drift. He was a Fellow of the Royal Society. Read more...
Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was a German-born American physicist considered a "father" of the presently accepted dynamo theory as an explanation of the Earth's magnetism. He proposed that this magnetic field resulted from electric currents induced in the fluid outer core of the Earth. He revealed the history of the Earth's magnetic field through pioneering the study of the magnetic orientation of minerals in rocks.
The Olin Hall at the Johns Hopkins University has a Walter Elsasser Memorial in the lobby. Read more...
Syukuro "Suki" Manabe (真鍋 淑郎, Manabe Shukurō, born September 21, 1931 in Ehime) is a meteorologist and climatologist who pioneered the use of computers to simulate global climate change and natural climate variations. Read more...- Gerhard Fanselau (30 April 1904, Leipzig – 28 April 1982, Potsdam) was a German geophysicist. Read more...
Claude (Jean) Allègre (French pronunciation: [klodaˈlɛɡʁ]; born 31 March 1937, Paris) is a French politician and scientist. Read more...
Fredrik Carl Mülertz Størmer (3 September 1874 – 13 August 1957) was a Norwegian mathematician and astrophysicist. In mathematics, he is known for his work in number theory, including the calculation of π and Størmer's theorem on consecutive smooth numbers. In physics, he is known for studying the movement of charged particles in the magnetosphere and the formation of aurorae, and for his book on these subjects, From the Depths of Space to the Heart of the Atom. He worked for many years as a professor of mathematics at the University of Oslo in Norway. A crater on the far side of the moon is named after him. Read more...
Patrick Maynard Stuart Blackett, Baron Blackett OM CH PRS (18 November 1897 – 13 July 1974) was a British experimental physicist known for his work on cloud chambers, cosmic rays, and paleomagnetism, winning the Nobel Prize for Physics in 1948. In 1925 he became the first person to prove that radioactivity could cause the nuclear transmutation of one chemical element to another. He also made a major contribution in World War II advising on military strategy and developing operational research. His left-wing views saw an outlet in third world development and in influencing policy in the Labour Government of the 1960s. Read more...- Inge Lehmann ForMemRS (13 May 1888 – 21 February 1993) was a Danish seismologist and geophysicist. In 1936, she discovered that the Earth has a solid inner core inside a molten outer core. Before that, seismologists believed Earth's core to be a single molten sphere, being unable, however, to explain careful measurements of seismic waves from earthquakes, which were inconsistent with this idea. Lehmann analysed the seismic wave measurements and concluded that Earth must have a solid inner core and a molten outer core to produce seismic waves that matched the measurements. Other seismologists tested and then accepted Lehmann's explanation. Lehmann was also the longest-lived woman scientist, having lived for over 104 years. Read more...
Sir Nicholas John Shackleton FRS (23 June 1937 – 24 January 2006) was an English geologist and paleoclimatologist who specialised in the Quaternary Period. He was the son of the distinguished field geologist Robert Millner Shackleton and great-nephew of the explorer Ernest Shackleton.
Educated at Cranbrook School, Kent (thanks to the generosity of a person he called his "fairy godmother" as she paid his school fees) Shackleton went on to read natural sciences at Clare College, Cambridge. He graduated with the Bachelor of Arts degree in 1961, promoted in 1964 to Master of Arts. In 1967 Cambridge awarded him a PhD degree, for a thesis entitled "The Measurement of Paleotemperatures in the Quaternary Era". Read more...
Abel Idowu Olayinka FAS (born February 16, 1958) is a Nigerian Professor of Applied geophysics. He is a former Deputy Vice Chancellor and the current Vice Chancellor of the University of Ibadan. He is also the President of the West African Research and Innovation Management Association.
In 2012, he was elected as fellow of the Nigerian Academy of Science, the apex academic organization in Nigeria. He was inducted into the academy, along with Professor Isaac Folorunso Adewole, the 11th substantive Vice Chancellor of the University of Ibadan, Professor Mojeed Olayide Abass, a Nigerian Professor of Computer science at the University of Lagos and Professor Akinyinka Omigbodun, the President of the West African College of Surgeons and former Provost of the College of Medicine, University of Ibadan. Read more...
Johann von Lamont FRSE, also referred to as Johann Lamont (13 December 1805 – 6 August 1879), was a Scottish-German astronomer and physicist. Read more...- Carl Wunsch was the Cecil and Ida Green Professor of Physical Oceanography at the Massachusetts Institute of Technology, until he retired in 2013. He is known for his early work in internal waves and more recently for research into the effects of ocean circulation on climate. Read more...
- Lloyd Viel Berkner (February 1, 1905 in Milwaukee, Wisconsin – June 4, 1967 in Washington, D.C.) was an American physicist and engineer. He was one of the inventors of the measuring device that since has become standard at ionospheric stations because it measures the height and electron density of the ionosphere. The data obtained in the worldwide net of such instruments were important for the developing theory of short wave radio propagation to which Berkner himself gave important contributions.
Later he investigated the development of the Earth's atmosphere. Since he needed data from the whole world, he proposed the International Geophysical Year in 1950. At that time, the IGY was the largest cooperative study of the Earth ever undertaken. Read more...
John Henry Pratt FRS (4 June 1809 – 28 December 1871) was a British clergyman, astronomer and mathematician. A Cambridge Apostle, he joined the British East India Company in 1838 as a chaplain and later became Archdeacon of Calcutta. Although nominated as Bishop of Calcutta, the decision was rescinded at the last moment with George Cotton being appointed to the position. A gifted mathematician who worked on problems of geodesy and earth science, he was approached by the Surveyor General of India to examine the errors in surveys resulting from the attraction of the plumb-line to the mass of the Himalayan mountains. This led him to develop a theory based on a fluid earth of crustal balance which became the basis for the isostasy principle. He died in India of cholera while on a visit to Ghazipur. Read more...
Charles Francis Richter (/ˈrɪktər/); April 26, 1900 – September 30, 1985) was an American seismologist and physicist.
Richter is most famous as the creator of the Richter magnitude scale, which, until the development of the moment magnitude scale in 1979, quantified the size of earthquakes. Inspired by Kiyoo Wadati's 1928 paper on shallow and deep earthquakes, Richter first used the scale in 1935 after developing it in collaboration with Beno Gutenberg; both worked at the California Institute of Technology. Read more...- Alessandro Serpieri (31 October 1823, San Giovanni in Marignano, near Rimini, – 22 February 1885, Fiesole) was an Italian scientist known for work in astronomy and seismology. Read more...
Marcia McNutt at the Royal Society admissions day in London, July 2017
Marcia Kemper McNutt (born February 19, 1952), ForMemRS, is an American geophysicist and the 22nd president of the National Academy of Sciences (NAS) of the United States. Previously, she served as editor-in-chief of the peer-reviewed journal Science from 2013 to 2016. McNutt holds a visiting appointment at the Scripps Institution of Oceanography. She is a member of the National Academies of Sciences, Engineering, and Medicine advisory committee for the Division on Earth and Life Studies and the Forum on Open Science. McNutt chaired the NASEM climate intervention committee who delivered two reports in 2015.
McNutt was the 15th director of the United States Geological Survey (USGS) (and first woman to hold the post) as well as science adviser to the United States Secretary of the Interior. Before working for USGS, McNutt was president and chief executive officer of the Monterey Bay Aquarium Research Institute (MBARI), an oceanographic research center in the United States, professor of marine geophysics at the Stanford University School of Earth Sciences and professor of marine geophysics at University of California, Santa Cruz. Read more...
A stamp of Zhang Heng issued by China Post in 1955
Zhang Heng (Chinese: 張衡; AD 78–139), formerly romanized as Chang Heng, was a Han Chinese polymath from Nanyang who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, scientist, engineer, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar.
Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court. His uncompromising stance on historical and calendrical issues led to his becoming a controversial figure, preventing him from rising to the status of Grand Historian. His political rivalry with the palace eunuchs during the reign of Emperor Shun (r. 125–144) led to his decision to retire from the central court to serve as an administrator of Hejian in Hebei. Zhang returned home to Nanyang for a short time, before being recalled to serve in the capital once more in 138. He died there a year later, in 139. Read more...
Erich Dagobert von Drygalski (February 9, 1865 – January 10, 1949) was a German geographer, geophysicist and polar scientist, born in Königsberg, Province of Prussia.
Between 1882 and 1887, Drygalski studied mathematics and natural science at the University of Königsberg, Bonn, Berlin and Leipzig. He graduated with a doctorate thesis about ice shields in Nordic areas. Between 1888 and 1891, he was an assistant at the Geodetic Institute and the Central Office of International Geodetics in Berlin. Read more...
William Bowie, B.S., C.E., M.A. (May 6, 1872 – August 28, 1940) was an American geodetic engineer. Read more...- William Richard Peltier, Ph.D., D.Sc. (hc) [1] (born 1943), is University Professor of Physics at the University of Toronto. He is director of the Centre for Global Change Science [2], past principal investigator of the Polar Climate Stability Network [3], and the Scientific Director of Canada's largest supercomputer centre, SciNet [4]. He is a fellow of the Royal Society of Canada, of the American Geophysical Union, of the American Meteorological Society, and of the Norwegian Academy of Science and Letters..
His research interests include: atmospheric and oceanic waves and turbulence, geophysical fluid dynamics, physics of the planetary interior, and planetary climate. Read more...
Luigi Palmieri (April 22, 1807 – September 9, 1896) was an Italian physicist and meteorologist. He was famous for his scientific studies of the eruptions of Mount Vesuvius, for his researches on earthquakes and meteorological phenomena and for improving the seismograph of the time. Read more...- Stanley Keith Runcorn FRS (19 November 1922 – 5 December 1995) was a British physicist whose paleomagnetic reconstruction of the relative motions of Europe and America revived the theory of continental drift and was a major contribution to plate tectonics. Read more...
- Anthony R. "Tony" Barringer (October 20, 1925 – August 15, 2009) was a Canadian/American geophysicist. He made numerous contributions to mineral exploration technology. His most famous work was the development of the INPUT airborne electromagnetic system, which has been credited in the discovery of tens of billions of dollars' worth of ore deposits.
Before beginning his university studies, Barringer served with the British Army in World War II. In 1948, he began attending the University of London. In 1951, he obtained a B.Sc. in economic geology from the university's Imperial College of Science and Technology. He obtained a PhD degree in 1954, from the same institution. Read more...
Harald Ulrik Sverdrup (15 November 1888 – 21 August 1957) was a Norwegian oceanographer and meteorologist.
He was director of Scripps Institution of Oceanography and director of the Norwegian Polar Institute. Read more...- Gordon James Fraser MacDonald (July 30, 1929 – May 14, 2002) was an American geophysicist and environmental scientist, best known for his principled skepticism regarding continental drift (now called plate tectonics), involvement in the development of the McNamara Line electronic defense barrier during the Vietnam War, and early research and advocacy on manmade global climate change. MacDonald was admired for his creative mind, and his ability to connect scientific issues and matters of public policy.
MacDonald was born in Mexico of a Scottish father and American mother. A childhood bout with polio only sharpened his competitive instincts. He applied to Harvard for a football scholarship and graduated summa cum laude at the age of 20. Remaining at Harvard, he became a Harvard Junior Fellow, then received his Ph.D. in geology in 1954. MacDonald was a faculty member at MIT (1954–1958), UCLA (1958–1966), UC Santa Barbara (1968–1970), Dartmouth (1972–1983) and UCSD (1990–1996). Read more...
Pierre Bouguer. Jean-Baptiste Perronneau, 1753.
Pierre Bouguer (French: [buˈge]) (16 February 1698, Croisic – 15 August 1758, Paris) was a French mathematician, geophysicist, geodesist, and astronomer. He is also known as "the father of naval architecture". Read more...
Thomas Wayland Vaughan (September 20, 1870 – January 16, 1952) was an American geologist and oceanographer. He worked with the United States Geological Survey and United States National Museum, investigating the geology of the West Indies, Panama Canal Zone, and the eastern coast of North America. In 1924 Vaughan became director of the Scripps Institution of Oceanography and held the post until his retirement in 1936. His research work concentrated on the study of corals and coral reefs, the investigation of larger foraminifera, and oceanography. Read more...
Portrait by Asta Nørregaard, 1900
Kristian Olaf Bernhard Birkeland (13 December 1867 – 15 June 1917) was a Norwegian scientist. He is best remembered for his theories of atmospheric electric currents that elucidated the nature of the aurora borealis. In order to fund his research on the aurorae, he invented the electromagnetic cannon and the Birkeland-Eyde process of fixing nitrogen from the air. Birkeland was nominated for the Nobel Prize seven times. Read more...
Paul Gordon Silver (November 30, 1948 – August 7, 2009) was an American seismologist.
A member of the research staff at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington since 1982, Paul Silver made a series of important contributions to the investigation of seismic anisotropy and to earthquake research by observing the slow redistribution of stress and strain along fault zones.
Paul Silver and his younger daughter Celine died in an automobile accident in North Carolina on August 7, 2009. Read more...- Henry Gellibrand (1597–1637) was an English mathematician. He is known for his work on the Earth's magnetic field. He discovered that magnetic declination – the angle of dip of a compass needle – is not constant but changes over time. He announced this in 1635, relying on previous observations by others, which had not yet been correctly interpreted.
He also devised a method for measuring longitude, based on eclipses. The mathematical tables of Henry Briggs, consisting of logarithms of trigonometric functions, were published by Gellibrand in 1633 as Trigonometria Britannica. Read more...
Alfred Lothar Wegener (/ˈveɪɡənər/; German: [ˈʔalfʁeːt ˈveːgənɐ]; 1 November 1880 – November 1930) was a German polar researcher, geophysicist and meteorologist.
During his lifetime he was primarily known for his achievements in meteorology and as a pioneer of polar research, but today he is most remembered as the originator of the theory of continental drift by hypothesizing in 1912 that the continents are slowly drifting around the Earth (German: Kontinentalverschiebung). His hypothesis was controversial and not widely accepted until the 1950s, when numerous discoveries such as palaeomagnetism provided strong support for continental drift, and thereby a substantial basis for today's model of plate tectonics. Wegener was involved in several expeditions to Greenland to study polar air circulation before the existence of the jet stream was accepted. Expedition participants made many meteorological observations and were the first to overwinter on the inland Greenland ice sheet and the first to bore ice cores on a moving Arctic glacier. Read more...
Morgan receiving the National Medal of Science from George W. Bush in 2003
William Jason Morgan (born October 10, 1935) is an American geophysicist who has made seminal contributions to the theory of plate tectonics and geodynamics. He retired as the Knox Taylor Professor emeritus of geology and professor of geosciences at Princeton University. He currently serves as a visiting scholar in the Department of Earth and Planetary Sciences at Harvard University. Read more...
Augustus Edward Hough Love FRS (17 April 1863, Weston-super-Mare – 5 June 1940, Oxford), often known as A. E. H. Love, was a mathematician famous for his work on the mathematical theory of elasticity. He also worked on wave propagation and his work on the structure of the Earth in Some Problems of Geodynamics won for him the Adams prize in 1911 when he developed a mathematical model of surface waves known as Love waves.
Love also contributed to the theory of tidal locking and introduced the parameters known as Love numbers, which are widely used today. These numbers are also used in problems related to the tidal deformation of the Earth due to the gravitational attraction of the Moon and Sun.
He was educated at Wolverhampton Grammar School and in 1881 won a scholarship to St John's College, Cambridge, where he was at first undecided whether to study classics or mathematics. His successful progress (he was placed Second Wrangler) vindicated his choice of mathematics, and in 1886 he was elected Fellow of the college. In 1899 he was appointed Sedleian Professor of Natural Philosophy in the University of Oxford, a position which he retained until his death in 1940. He was also a Fellow of Queen's College. Read more...- Marion King Hubbert (October 5, 1903 – October 11, 1989) was an American geologist and geophysicist. He worked at the Shell research lab in Houston, Texas. He made several important contributions to geology, geophysics, and petroleum geology, most notably the Hubbert curve and Hubbert peak theory (a basic component of peak oil), with important political ramifications. He was often referred to as "M. King Hubbert" or "King Hubbert". Read more...
- Pierre Perrault (c. 1608 in Paris – 1680 in Paris) was a Receiver General of Finances for Paris and later a scientist who developed the concept of the hydrological cycle. He and Edme Mariotte were primarily responsible for making hydrology an experimental science. Read more...
- Louise H. Kellogg (1959–) is an American geophysicist with expertise in chemical geodynamics and computational geophysics and experience in leading multidisciplinary teams to advance geodynamics modeling and scientific visualization. Kellogg is a professor at the University of California, Davis and director of Computational Infrastructure for Geodynamics. Read more...
- Tanya Atwater (born 1942) is a professor emeritus, American geophysicist and marine geologist, who specializes in plate tectonics, in particular the evolution of the San Andreas Fault plate boundary. Her work focused on the creation of computer-animated multimedia products and presentations depicting the histories of tectonic plates. Read more...
- Bernhard Haurwitz (August 14, 1905 – February 27, 1986) was a German-born American meteorologist and physicist. Haurwitz was Chair of Department of Meteorology at New York University (NYU), a member of the National Academy of Sciences (NAS), a recipient of Carl-Gustaf Rossby Research Medal Awarded the William Bowie Medal in 1970. Read more...
- Edward A. "Ted" Irving, CM FRSC FRS (27 May 1927 – 25 February 2014) was a geologist and scientist with the Geological Survey of Canada. His studies of paleomagnetism provided the first physical evidence of the theory of continental drift. His efforts contributed to our understanding of how mountain ranges, climate, and life have changed over the past millions of years. Read more...
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Selected images
Computer simulation of the Earth's magnetic field in a period of normal polarity between reversals.
Schematic representation of spherical harmonics on a sphere and their nodal lines. Pℓ m is equal to 0 along m great circles passing through the poles, and along ℓ-m circles of equal latitude. The function changes sign each ℓtime it crosses one of these lines.
A depiction of atmospheric electricity in a Martian dust storm, which has been suggested as a possible explanation for enigmatic chemistry results from Mars (see also Viking lander biological experiments)
World map showing frequency of lightning strikes, in flashes per km² per year (equal-area projection). Lightning strikes most frequently in the Democratic Republic of the Congo. Combined 1995–2003 data from the Optical Transient Detector and 1998–2003 data from the Lightning Imaging Sensor.
World map showing the position of the Moho.
Background: a set of traces from magnetic observatories showing a magnetic storm in 2000.
Globe: map showing locations of observatories and contour lines giving horizontal magnetic intensity in μ T.Computer simulation of the Earth's field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth's core.
Geomagnetic polarity during the late Cenozoic Era. Dark areas denote periods where the polarity matches today's polarity, light areas denote periods where that polarity is reversed.
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