Earth’s core is the very hot, really dense facility of our planet. The ball-shaped main point lies beneath the cool, brittle crust and also the mostly-solid mantle. The core is found about 2,900 kilometers (1,802 miles) below Earth’s surface, and also has a radius of about 3,485 kilometers (2,165 miles).

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Planet planet is older 보다 the core. When planet was formed about 4.5 billion year ago, it to be a uniform round of warm rock. Radioactive decay and leftover warmth from planetary formation (the collision, accretion, and compression of room rocks) brought about the ball to get even hotter. Eventually, after around 500 million years, ours young planet’s temperature heated come the melting suggest of iron—about 1,538° Celsius (2,800° Fahrenheit). This pivotal moment in Earth’s background is referred to as the iron catastrophe.
The steel catastrophe enabled greater, much more rapid motion of Earth’s molten, rocky material. Relatively buoyant material, such as silicates, water, and even air, remained close to the planet’s exterior. These materials ended up being the early mantle and crust. Droplets the iron, nickel, and also other hefty metals gravitated come the facility of Earth, becoming the early on core. This important procedure is dubbed planetary differentiation.
Earth’s core is the heater of the geothermal gradient. The geothermal gradient measures the rise of heat and also pressure in Earth’s interior. The geothermal gradient is about 25° Celsius per kilometre of depth (1° Fahrenheit every 70 feet). The major contributors to warm in the core space the decay of radioactive elements, leftover heat from planetary formation, and heat released as the liquid external core solidifies near its boundary with the inside core.
Unlike the mineral-rich crust and mantle, the main point is made virtually entirely the metal—specifically, iron and nickel. The shorthand offered for the core’s iron-nickel alloys is just the elements’ chemistry symbols—NiFe.
Elements the dissolve in iron, called siderophiles, are additionally found in the core. Because these facets are discovered much much more rarely on Earth’s crust, plenty of siderophiles are classified together “precious metals.” Siderophile elements include gold, platinum, and cobalt.
Another key element in Earth’s main point is sulfur—in truth 90% of the sulfur on earth is found in the core. The confirmed discovery of such huge amounts of sulfur helped define a geologic mystery: If the main point was primarily NiFe, why wasn’t the heavier? Geoscientists speculated that lighter elements such together oxygen or silicon could have to be present. The diversity of sulfur, another fairly light element, described the conundrum.
Although we know that the main point is the hottest part of our planet, its precise temperatures are complicated to determine. The fluctuating temperatures in the core count on pressure, the rotation the the Earth, and the differing composition of main point elements. In general, temperatures selection from around 4,400° Celsius (7,952° Fahrenheit) to around 6,000° Celsius (10,800° Fahrenheit).
The core is do of 2 layers: the outer core, which borders the mantle, and the inside core. The border separating these areas is called the Bullen discontinuity.
The outer core, around 2,200 kilometers (1,367 miles) thick, is mostly composed of fluid iron and nickel. The NiFe alloy the the outer core is very hot, between 4,500° and 5,500° Celsius (8,132° and 9,932° Fahrenheit).
The liquid steel of the external core has really low viscosity, definition it is easily deformed and malleable. That is the site of violent convection. The churning steel of the outer core creates and also sustains Earth’s magnetic field.
The hottest part of the core is in reality the Bullen discontinuity, wherein temperatures reach 6,000° Celsius (10,800° Fahrenheit)—as hot as the surface ar of the sun.
The inner core is a hot, thick ball the (mostly) iron. It has a radius of about 1,220 kilometers (758 miles). Temperature in the inner main point is around 5,200° Celsius (9,392° Fahrenheit). The push is virtually 3.6 million atmosphere (atm).
The temperature of the inner core is far over the melting suggest of iron. However, unlike the outer core, the inner core is no liquid or even molten. The within core’s intense pressure—the entire rest that the planet and its atmosphere—prevents the iron native melting. The pressure and density are just too great for the iron atom to move right into a liquid state. As such unusual set of circumstances, part geophysicists choose to analyze the inner core not together a solid, but as a plasma behaving as a solid.
The liquid outer core off the inner core from the rest of the Earth, and as a result, the inner core rotates a little differently than the rest of the planet. That rotates eastward, like the surface, yet it’s a little faster, making an extra rotation about every 1,000 years.
Geoscientists think that the steel crystals in the inside core room arranged in an “hcp” (hexagonal close-packed) pattern. The crystals align north-south, together with Earth’s axis the rotation and also magnetic field.
The orientation of the crystal structure way that seismic waves—the many reliable way to research the core—travel much faster when walk north-south than when going east-west. Seismic tide travel four seconds much faster pole-to-pole than v the Equator.
As the entire planet slowly cools, the inner main point grows by around a millimeter every year. The inner core grows together bits that the liquid outer core solidify or crystallize. An additional word because that this is “freezing,” return it’s necessary to remember that iron’s freezing point much more than 1,000° Celsius (1,832° Fahrenheit).
The growth of the inner main point is no uniform. It occurs in lumps and also bunches, and is influenced by activity in the mantle.
Growth is an ext concentrated about subduction zones—regions whereby tectonic plates are slipping native the lithosphere into the mantle, hundreds of kilometers over the core. Subducted plates attract heat indigenous the core and also cool the surrounding area, causing boosted instances that solidification.
Growth is less concentrated approximately “superplumes” or LLSVPs. These ballooning masses that superheated mantle rock likely affect “hot spot” volcanism in the lithosphere, and also contribute to a much more liquid outer core.
The core will never “freeze over.” The crystallization procedure is really slow, and also the continuous radioactive degeneration of Earth’s interior slows it also further. Researchers estimate it would certainly take about 91 exchange rate years because that the main point to completely solidify—but the sun will burn the end in a portion of that time (about 5 billion years).
Just like the lithosphere, the inner main point is separated into eastern and western hemispheres. These hemispheres don’t melt evenly, and also have unique crystalline structures.
The western hemisphere seems to be crystallizing an ext quickly 보다 the east hemisphere. In fact, the east hemisphere that the inner core might actually it is in melting.
Geoscientists recently found that the inner core itself has actually a core—the within inner core. This strange function differs indigenous the inner main point in lot the same method the inner main point differs from the outer core. Researchers think that a radical geologic change about 500 million years back caused this inner inner core to develop.
The crystals that the inside inner core are oriented east-west rather of north-south. This orientation is no aligned with either Earth’s rotational axis or magnetic field. Scientists think the iron crystals may even have a completely different framework (not hcp), or exist in ~ a different phase.
Earth’s magnetic field is created in the swirling outer core. Magnetism in the external core is around 50 times stronger than the is top top the surface.
It can be simple to think the Earth’s magnetism is resulted in by the huge ball the solid stole in the middle. However in the inside core, the temperature is for this reason high the magnetism of stole is altered. As soon as this temperature, called the Curie point, is reached, the atoms of a substance have the right to no much longer align come a magnetic point.
Some geoscientists define the outer core as Earth’s “geodynamo.” for a earth to have actually a geodynamo, it need to rotate, that must have a liquid medium in its interior, the fluid must be able to conduct electricity, and it must have actually an internal power supply that drives convection in the liquid.
Variations in rotation, conductivity, and also heat affect the magnetic field of a geodynamo. Mars, because that instance, has actually a entirely solid core and also a weak magnetic field. Venus has actually a liquid core, but rotates too gradually to churn far-reaching convection currents. It, too, has a weak magnetic field. Jupiter, ~ above the various other hand, has a liquid main point that is continuous swirling due to the planet’s rapid rotation.
Earth is the “Goldilocks” geodynamo. That rotates steadily, in ~ a fast 1,675 kilometers per hour (1,040 miles per hour) at the Equator. Coriolis forces, one artifact the Earth’s rotation, reason convection currents to it is in spiral. The liquid iron in the external core is fantastic electrical conductor, and also creates the electrical currents the drive the magnetic field.
The power supply that drives convection in the outer core is detailed as droplets of fluid iron freeze onto the hard inner core. Solidification releases warm energy. This heat, in turn, provides the staying liquid iron an ext buoyant. Warmer liquids spiral upward, while cooler solids spiral downward under extreme pressure: convection.
Earth’s magnetic ar is an important to life on ours planet. It protects the world from the charged particles the the solar wind. There is no the shield the the magnetic field, the solar wind would certainly strip Earth’s environment of the ozone layer that protects life from harmfulultraviolet radiation.
Although Earth’s magnetic ar is generally stable, that fluctuates constantly. Together the liquid outer core moves, for instance, that can adjust the ar of the magnetic North and South Poles. The magnetic north Pole moves as much as 64 kilometers (40 miles) every year.
Fluctuations in the main point can cause Earth’s magnetic ar to adjust even much more dramatically. Geomagnetic pole reversals, because that instance, happen around every 200,000 come 300,000 years. Geomagnetic pole reversals are just what they sound like: a readjust in the planet’s magnetic poles, so the the magnetic North and South Poles space reversed. This “pole flips” space not catastrophic—scientists have detailed no real changes in tree or pet life, glacial activity, or volcano eruptions throughout previous geomagnetic pole reversals.
Geoscientists cannot examine the core directly. Every information about the core has actually come from sophisticated reading of seismic data, evaluation of meteorites, lab experiments with temperature and pressure, and also computer modeling.
Most main point research has been carried out by measure up seismic waves, the shock tide released by earthquakes at or close to the surface. The velocity and also frequency that seismic body waves changes with pressure, temperature, and rock composition.
In fact, seismic waves assisted geoscientists determine the framework of the core itself. In the so late 19th century, scientists provided a “shadow zone” deep in the Earth, whereby a type of body wave called an s-wave one of two people stopped entirely or to be altered. S-waves space unable come transmit with fluids or gases. The sudden “shadow” where s-waves disappeared suggested that earth had a fluid layer.
In the 20th century, geoscientists discovered an increase in the velocity of p-waves, another kind of human body wave, at about 5,150 kilometers (3,200 miles) below the surface. The rise in velocity synchronized to a change from a fluid or molten medium to a solid. This showed the existence of a hard inner core.
Meteorites, room rocks that crash to Earth, also provide clues around Earth’s core. Many meteorites are pieces of asteroids, rocky bodies the orbit the sun between Mars and also Jupiter. Asteroids formed about the very same time, and also from about the same material, as Earth. By examining iron-rich chondrite meteorites, geoscientists can acquire a peek into the early formation of ours solar system and also Earth’s beforehand core.
In the lab, the most an useful tool for researching forces and also reactions in ~ the core is the diamond anvil cell. Diamond anvil cells usage the hardest problem on planet (diamonds) come simulate the extremely high push at the core. The machine uses one x-ray laser to simulate the core’s temperature. The laser is beamed with two diamonds squeezing a sample between them.
Complex computer system modeling has also allowed scientists to research the core. In the 1990s, for instance, modeling beautifully portrayed the geodynamo—complete through pole flips.
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Although the inner core is greatly NiFe, the iron catastrophe likewise drove heavy siderophile aspects to the facility of the Earth. In fact, one geoscientist calculated that there are 1.6 quadrillion tons of yellow in the core—that’s sufficient to gild the entire surface that the world half-a-meter (1.5 feet) thick.
One of the many bizarre ways geoscientists examine the main point is through “geoneutrinos.” Geoneutrinos space neutrinos, the lightest subatomic particle, exit by the herbal radioactive degeneration of potassium, thorium, and also uranium in Earth’s interior. By examining geoneutrinos, researchers can far better understand the composition and also spatial circulation of products in the mantle and core.
“Subterranean fiction” describes adventure stories occurring deep listed below the surface of the Earth. Jules Verne’s Journey to the center of the Earth is more than likely the most popular piece of subterranean fiction. Other examples include Dante Alighieri’s Divine Comedy, in i m sorry the deepest facility of planet is Hell itself; the movie Ice Age: Dawn that the Dinosaurs, in i beg your pardon an secret world enables dinosaurs come survive right into the existing day; and also the rabbit hole the Alice’s Adventures in Wonderland—which was initially titled Alice’s Adventures Under Ground.
Inge Lehman, who referred to as herself “the only Danish seismologist” functioning in the 1930s, to be a pioneering number in the examine of Earth’s interior. Lehman to be the very first to determine Earth’s hard inner core, and became a leading experienced in the structure of the upper mantle as well. She was the an initial woman to obtain the prestigious wilhelm Bowie Medal, the highest honor awarded by the American Geophysical Union. In 1997, the AGU produced the Inge Lehman Medal, recognizing a scientist’s “outstanding contribute to the knowledge of the structure, composition, and dynamics of the Earth"s mantle and also core.”

Planetary CoresAll well-known planets have actually metal cores. Even the gas giants of our solar system, such as Jupiter and also Saturn, have iron and nickel at their cores.


process of examining a problem or situation, identify its characteristics and also how they are related.


irregularly shame planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.


(atm) unit the measurement same to air pressure at sea level, about 14.7 pounds every square inch. Additionally called traditional atmospheric pressure.


type of mineral that is clear and, as soon as viewed under a microscope, has a repeating sample of atoms and also molecules.


temperature at which a ferromagnetic product loses that is ferromagnetism—its capability to own magnetism in the absence of a magnetic field.


the sudden shaking that Earth"s crust resulted in by the release of power along fault lines or from volcano activity.


temperature at which liquid becomes solid; the freezing allude of water is 0 levels Celsius (32 levels Fahrenheit).


change in a celestial body"s magnetic ar so that the magnetic North and South Poles room switched.


gradual change in temperature indigenous the Earth"s main point (hot) to its crust (cool), around 25° Celsus per kilometer of depth (1° Fahrenheit per 70 feet of depth).


intensely hot region deep within the planet that rises to just underneath the surface. Some hot spots develop volcanoes.


oddly crystallized structure at the heart of ours planet, through iron crystals oriented east-west instead of north-south (as v the inner core).


(~4 billion years ago) allude in Earth"s planetary formation when the temperature reached the melting point of iron and also heavy aspects (mostly iron and also nickel) gravitated towards the center of the planet.


(acronym for light amplification by engendered emission that radiation) an instrument the emits a thin beam that light that does not fade over long distances.


(large short shear velocity province) seismically anomalous region at the deepest component of Earth"s mantle. Also called a superplume or thermo-chemical pile.


able to produce a force field that can lure or repel details substances, usually metals (magnets).


layer in the environment containing the gas ozone, which absorbs many of the sun"s ultraviolet radiation.


seismic shock wave that represents longitudinal motion. Also called a major wave or press wave.


transformation that an rough atomic nucleus right into a lighter one, in which radiation is released in the type of alpha particles, beta particles, gamma rays, and also other particles. Likewise called radioactivity.


flow of charged particles, greatly protons and electrons, from the sun to the sheet of the solar system.


seismic shock wave that to represent perpendicular motion. Additionally called a an additional wave or shear wave.


massive slab of hard rock comprised of Earth"s lithosphere (crust and upper mantle). Additionally called lithospheric plate.


powerful light waves that are too brief for human beings to see, however can pass through Earth"s atmosphere. Ultraviolet is often shortened to UV.

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upward motion of molten product from in ~ the earth to the surface, where it cools and also hardens.


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