Frank Donald Stacey (21 August 1929, Essex, UK) is an English-born Australian geophysicist, known for his research on rock magnetism [1] and application of thermodynamics to understanding the Earth's core and mantle. [2] [3] [1]
At the University of London, Stacey graduated with a B.Sc. in 1950 and a Ph.D. in 1953. As a postdoc, he was from 1953 to 1956 a research fellow at the University of British Columbia in Vancouver. From 1961 to 1964 he was a Royal Society Gassiot Fellow in Geomagnetism at the Meteorological Office Research Unit of the University of Cambridge. [4] Near the beginning of his career he published several papers in The Philosophical Magazine . [5] [6] [7] [8] He was a Reader in Physics at the University of Queensland from 1964 to 1971 [4] — during those years he wrote the first three editions of Physics of the Earth. [9] (In 1988 a fourth edition was published with Paul McEwan Davis as co-author. [9] ) In 1968 Stacey received his D.Sc. from the University of London. From 1971 to 1990 he was a professor of Applied Physics at the University of Queensland. [4] He was appointed to visiting lectureships in several different countries. In 1997 he joined the Australian Government agency CSIRO Exploration and Mining. [9]
Louis Néel’s 1955 paper Some theoretical aspects of rock-magnetism [10] inspired Stacey to generalize Néel's single-domain theory for magnetic grains to multi-domained grains. In the theory of remanence for igneous rocks, Stacey introduced the concept of pseudo-single domain for magnetic grains which are small and multi-domained. [1] [11] He did research on scientifically describing rock fabric using magnetic anisotropy [1] [12] and predicting earthquakes and volcanic eruptions using piezomagnetism. [1] [13] [14] With several colleagues, Stacey investigated possible failures of Newton's law of gravity. [15] [16] [17] [18] [19] [20]
Using a lattice dynamical formulation for the Grüneisen parameter, he developed a new equation of state for high pressures with applications to materials in the Earth's core and lower mantle. [1] [21] His book Physics of the Earth became a widely used, standard textbook and was the first geophysics textbook to comprehensively deal with solid Earth geophysics. [1]
Stacey chaired from 1966 to 1967 the Australian Institute of Physics, Queensland branch. He was elected in 1979 a Fellow of the Australian Academy of Science [4] and in 1986 a Fellow der American Geophysical Union. [22] In 1994 he was awarded the Louis Néel Medal. [1]
Geophysics 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. Geophysicists, who usually study geophysics, physics, or one of the Earth sciences at the graduate level, complete investigations across a wide range of scientific disciplines. The term geophysics classically refers to solid earth applications: Earth's shape; its gravitational, magnetic fields, and electromagnetic 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 and pure scientists 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 physics; and analogous problems associated with the Moon and other planets.
Earth's outer core is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. The outer core begins approximately 2,889 km (1,795 mi) beneath Earth's surface at the core-mantle boundary and ends 5,150 km (3,200 mi) beneath Earth's surface at the inner core boundary.
A planetary core consists of the innermost layers of a planet. Cores may be entirely liquid, or a mixture of solid and liquid layers as is the case in the Earth. In the Solar System, core sizes range from about 20% to 85% of a planet's radius (Mercury).
The core–mantle boundary (CMB) of Earth lies between the planet's silicate mantle and its liquid iron–nickel outer core, at a depth of 2,891 km (1,796 mi) below Earth's surface. The boundary is observed via the discontinuity in seismic wave velocities at that depth due to the differences between the acoustic impedances of the solid mantle and the molten outer core. P-wave velocities are much slower in the outer core than in the deep mantle while S-waves do not exist at all in the liquid portion of the core. Recent evidence suggests a distinct boundary layer directly above the CMB possibly made of a novel phase of the basic perovskite mineralogy of the deep mantle named post-perovskite. Seismic tomography studies have shown significant irregularities within the boundary zone and appear to be dominated by the African and Pacific Large low-shear-velocity provinces (LLSVP).
A geomagnetic reversal is a change in a planet's dipole magnetic field such that the positions of magnetic north and magnetic south are interchanged. The Earth's magnetic field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons.
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon's radius.
Omphacite is a member of the clinopyroxene group of silicate minerals with formula: (Ca, Na)(Mg, Fe2+, Al)Si2O6. It is a variably deep to pale green or nearly colorless variety of clinopyroxene. It normally appears in eclogite, which is the high-pressure metamorphic rock of basalt. Omphacite is the solid solution of Fe-bearing diopside and jadeite. It crystallizes in the monoclinic system with prismatic, typically twinned forms, though usually anhedral. Its space group can be P2/n or C2/c depending on the thermal history. It exhibits the typical near 90° pyroxene cleavage. It is brittle with specific gravity of 3.29 to 3.39 and a Mohs hardness of 5 to 6.
The Journal of Geophysical Research is a peer-reviewed scientific journal. It is the flagship journal of the American Geophysical Union. It contains original research on the physical, chemical, and biological processes that contribute to the understanding of the Earth, Sun, and Solar System. It has seven sections: A, B, C (Oceans), D (Atmospheres), E (Planets), F, and G (Biogeosciences). All current and back issues are available online for subscribers.
Wadsleyite is an orthorhombic mineral with the formula β-(Mg,Fe)2SiO4. It was first found in nature in the Peace River meteorite from Alberta, Canada. It is formed by a phase transformation from olivine (α-(Mg,Fe)2SiO4) under increasing pressure and eventually transforms into spinel-structured ringwoodite (γ-(Mg,Fe)2SiO4) as pressure increases further. The structure can take up a limited amount of other bivalent cations instead of magnesium, but contrary to the α and γ structures, a β structure with the sum formula Fe2SiO4 is not thermodynamically stable. Its cell parameters are approximately a = 5.7 Å, b = 11.71 Å and c = 8.24 Å.
Pyrolite is a term used to characterize a model composition of the Earth's mantle. This model is based on that a pyrolite source can produce mid-ocean ridge basalts (MORB) by partial melting. It was first proposed by Ted Ringwood (1962) as being 1 part basalt and 4 parts harzburgite, but later was revised to being 1 part tholeiitic basalt and 3 parts dunite. The term is derived from the mineral names PYR-oxene and OL-ivine. However, whether pyrolite is entirely representative of the Earth's mantle remains debated.
The historical development of geophysics has been motivated by two factors. One of these is the research curiosity of humankind related to planet Earth and its several components, its events and its problems. The second is economical usage of Earth's resources and Earth-related hazards such as earthquakes, volcanoes, tsunamis, tides, and floods.
(Stanley) Keith Runcorn 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.
Earth's internal heat budget is fundamental to the thermal history of the Earth. The flow heat from Earth's interior to the surface is estimated at 47±2 terawatts (TW) and comes from two main sources in roughly equal amounts: the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust, and the primordial heat left over from the formation of Earth.
In geology, numerical modeling is a widely applied technique to tackle complex geological problems by computational simulation of geological scenarios.
Inner core super-rotation is the eastward rotation of the inner core of Earth relative to its mantle, for a net rotation rate that is usually faster than Earth as a whole. A 1995 model of Earth's dynamo predicted super-rotations of up to 3 degrees per year; the following year, this prediction was supported by observed discrepancies in the time that p-waves take to travel through the inner and outer core.
The lower mantle, historically also known as the mesosphere, represents approximately 56% of Earth's total volume, and is the region from 660 to 2900 km below Earth's surface; between the transition zone and the outer core. The preliminary reference Earth model (PREM) separates the lower mantle into three sections, the uppermost (660–770 km), mid-lower mantle (770–2700 km), and the D layer (2700–2900 km). Pressure and temperature in the lower mantle range from 24–127 GPa and 1900–2600 K. It has been proposed that the composition of the lower mantle is pyrolitic, containing three major phases of bridgmanite, ferropericlase, and calcium-silicate perovskite. The high pressure in the lower mantle has been shown to induce a spin transition of iron-bearing bridgmanite and ferropericlase, which may affect both mantle plume dynamics and lower mantle chemistry.
Susan Halgedahl is a geologist known for her research into the physics that govern magnetic rocks and for her work on fossils from Utah's Wheeler Formation.
Subir Kumar Banerjee is an Indian-American geophysicist, known for research on rock magnetism, palaeomagnetism, and environmental magnetism.
Seismic velocity structure is the distribution and variation of seismic wave speeds within Earth's and other planetary bodies' subsurface. It is reflective of subsurface properties such as material composition, density, porosity, and temperature. Geophysicists rely on the analysis and interpretation of the velocity structure to develop refined models of the subsurface geology, which are essential in resource exploration, earthquake seismology, and advancing our understanding of Earth's geological development.
David A. Bercovici is an American geophysicist. He is primarily known for his theoretical explanations of why planet Earth has plate tectonics. He is also known for his development of models of how the Earth's mantle recycles and stores water and how such hydrological processes are involved in Earth's geochemical history.