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 tectonicsthe generation of magmasvolcanism and rock formation.
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 lodestoneswhile more modern magnetic compasses played an important role in the history of navigation. The first seismic instrument was built in AD. Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox ;
Geofisica definicion yahoo dating 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. Geophysics is applied to societal needs, such as mineral resourcesmitigation of natural hazards and environmental protection. Geophysics is a highly interdisciplinary subject, and geophysicists contribute to every area of the Earth sciences.
To provide a clearer idea of what constitutes geophysics, this section describes phenomena that are studied in physics and how they Geofisica definicion yahoo dating to the Earth and its surroundings. The gravitational pull of the Moon and Sun give rise to two high tides and two low tides every lunar day, or every 24 hours and 50 minutes. Therefore, there is a gap of 12 hours and 25 minutes between every high tide and between every low tide.
Gravitational forces make rocks press down on deeper rocks, increasing their density as the depth increases. The geopotential surface called the geoid is one definition of the shape of the Earth. The geoid would be the global mean sea level if the oceans were in "Geofisica definicion yahoo dating" and could be extended through the continents such as with
Geofisica definicion yahoo dating narrow canals.
Geofisica definicion yahoo dating Earth is cooling, and the resulting heat Geofisica definicion yahoo dating generates the Earth's magnetic field through the geodynamo and plate tectonics through mantle convection.
Heat is mostly carried to the surface by thermal convectionalthough there are two thermal boundary layers — the core-mantle boundary and the lithosphere — in which heat is transported by conduction.
The heat flow at the Earth's surface is about 4. Seismic waves are vibrations that travel through the Earth's interior or along its surface. The entire Earth can also oscillate in forms that are called normal modes or free oscillations of the Earth. Ground motions from waves or normal modes are measured using seismographs.
If the waves come from a localized source such as an earthquake or explosion, measurements at more than one location can be used to locate the source. The locations of Geofisica definicion yahoo dating provide information on plate tectonics and mantle convection. Measurements of seismic waves are a source of information on the region that the waves travel through. If the density or composition of the rock changes suddenly, some waves are reflected. Reflections can provide information on near-surface structure.
Earthquakes pose a risk to humans. Understanding their mechanisms, which
Geofisica definicion yahoo dating on the type of earthquake e. Although we mainly notice electricity during thunderstormsthere is always a downward electric field near the surface that averages volts per meter. A current of about amperes flows in the global circuit. The flow is manifested by lightning below the clouds and sprites above.
A variety of electric methods are used in geophysical survey. Some measure spontaneous potential
Geofisica definicion yahoo dating potential that arises in the ground because of man-made or natural disturbances. Telluric currents flow in Earth and the Geofisica definicion yahoo dating. They have two causes: Geophysicists can also provide the electric current themselves see induced polarization and electrical resistivity tomography. Electromagnetic waves occur in the ionosphere and magnetosphere as well as the Earth's outer core.
Dawn chorus is believed to be caused by high-energy electrons that get caught in the Van Allen radiation belt. Whistlers are produced by lightning strikes. Hiss may be generated by both. Electromagnetic waves may also be generated by earthquakes see seismo-electromagnetics. In the highly conductive liquid iron of the outer core, magnetic fields are generated by electric currents through electromagnetic induction.
In the core, they probably have little observable effect on the Earth's magnetic field, but slower waves such as magnetic Rossby waves may be one source of geomagnetic secular variation.
Electromagnetic methods that are used for geophysical survey include transient electromagneticsmagnetotellurics and electromagnetic seabed logging. The Earth's magnetic field protects the Earth from the deadly solar wind and has long been used for navigation.
It originates in the fluid motions of the outer core. The Earth's field is roughly like a tilted dipolebut it changes over time a phenomenon called geomagnetic secular variation.
Mostly the geomagnetic pole stays near the geographic polebut at random intervals averagingto a million years or so, the polarity of the Earth's field reverses. These geomagnetic reversalsanalyzed within a Geomagnetic Polarity Time Scalecontain polarity intervals in the last 83 million years, with change in frequency over time, with the most recent Geofisica definicion yahoo dating complete reversal of the Laschamp event occurring 41, years ago during the last glacial period.
Geologists observed geomagnetic reversal recorded in volcanic rocks, Geofisica definicion yahoo dating magnetostratigraphy correlation see natural remanent magnetization and their signature can be seen as parallel linear Geofisica definicion yahoo dating anomaly stripes on the seafloor. These stripes provide quantitative on seafloor spreadinga part of plate tectonics.
They are the basis of magnetostratigraphywhich correlates magnetic reversals with other stratigraphies Geofisica definicion yahoo dating construct geologic time scales. Unstable isotopes decay at predictable rates, and the decay rates of different isotopes cover several orders of magnitude, so radioactive decay can be used to accurately date both recent events and events in past geologic eras.
Fluid motions occur in the magnetosphere, atmosphereocean, mantle and core. Even the mantle, though it has an enormous viscosityflows like Geofisica definicion yahoo dating fluid over long time intervals. This flow is reflected in phenomena such as isostasypost-glacial rebound and mantle plumes. The mantle flow drives plate tectonics and the flow in the Earth's core drives the geodynamo.
Geophysical fluid dynamics is a primary tool in physical oceanography and meteorology. The rotation of the Earth has profound effects on the Earth's fluid dynamics, often due to the Coriolis effect.
In the atmosphere it gives rise to large-scale patterns like Rossby waves and determines the basic circulation patterns of storms. In the ocean they drive large-scale circulation patterns as well as Kelvin waves and Ekman spirals at the ocean surface. Waves and other phenomena in the magnetosphere can be modeled using magnetohydrodynamics.
The physical properties of minerals must be understood to infer the composition of the Earth's interior from seismologythe geothermal gradient and other sources of information. Mineral physicists study the elastic properties of minerals; their high-pressure phase diagramsmelting points and equations of state at high pressure; and the rheological properties of rocks, or their ability to flow.
Deformation of rocks by creep make flow possible, although over short times the rocks are brittle. The viscosity of rocks is affected by temperature and pressure, and in turn determines the rates at which tectonic plates move.
Geofisica definicion yahoo dating is a very complex substance and its unique properties are essential for life. Its thermodynamic properties determine evaporation and the thermal gradient in the Geofisica definicion yahoo dating. The many types of precipitation involve a complex mixture of processes such as coalescencesupercooling and supersaturation.
Physical properties of water such as salinity have a "Geofisica definicion yahoo dating" effect on its motion in the oceans.
The many phases of ice form the cryosphere and come in forms like ice sheetsglacierssea icefreshwater ice, snow, and frozen ground or permafrost. The Earth is roughly spherical, but it bulges towards the so it is roughly in the shape of an ellipsoid see Earth ellipsoid.
This bulge is due to its rotation and is nearly consistent with an Earth in hydrostatic equilibrium. The Geofisica definicion yahoo dating shape of the Earth, however, is also affected by the distribution of continents and ocean basinsand to some extent by the dynamics of the plates. Evidence from seismology, heat flow at the surface, and mineral physics is combined with the Earth's mass and moment of inertia to infer models of the Earth's interior — its composition, density, temperature, pressure.
For example, the Earth's mean specific gravity 5. This is also implied by its low moment of inertia 0. However, some of the density increase is compression under the enormous pressures inside the Earth.
The effect of pressure can be calculated using the Adams—Williamson equation.
The conclusion is that pressure alone cannot account for the increase in density. Instead, we know that the Earth's core is composed of an alloy of Geofisica definicion yahoo dating and other minerals. Reconstructions of seismic Geofisica definicion yahoo dating in the deep interior of the Earth show that there are no S-waves in the outer core.
This indicates that the outer core is liquid, because liquids cannot support shear. The outer core is liquid, and the motion of this highly conductive fluid generates the Earth's field.
The inner corehowever, is solid because of the enormous pressure. Reconstruction of seismic reflections in the deep interior indicate some major discontinuities in seismic velocities that demarcate the major zones of the Earth: The seismic model of the Earth does not by itself determine the composition of "Geofisica definicion yahoo dating" layers.
For a complete model of the Earth, mineral physics is needed to interpret seismic velocities in terms of composition. The mineral properties are temperature-dependent, so the geotherm must also be determined. This requires physical theory for thermal conduction and convection and the heat contribution of radioactive elements.
Some parts of this model have been updated by Geofisica definicion yahoo dating findings in mineral physics see post-perovskite and supplemented by seismic tomography.
The mantle is mainly composed of silicatesand the boundaries between layers of the mantle are consistent with phase transitions. The mantle acts as a solid for seismic waves, but under high pressures and temperatures it deforms so that over millions of years it acts like a liquid. This makes plate tectonics possible. If a planet's magnetic field is Geofisica definicion yahoo dating enough, its interaction with the solar wind forms a magnetosphere.
Early space probes mapped out the gross dimensions of the Earth's Geofisica definicion yahoo dating field, which extends about 10 Earth radii towards the Sun. The solar wind, a stream of charged particles, streams out and around the terrestrial magnetic field, and continues behind the magnetic tailhundreds of Earth radii downstream.
Inside the magnetosphere, there are relatively dense regions of solar wind particles called the Van Allen radiation belts. Geophysical measurements are generally at a particular time and place. Main · Videos; Dambrete online dating michael weatherly dating · geofisica definicion yahoo dating · kim kardashian tired dating pro athletes · internet.
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