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

You are watching: The densest layer of earth is the

Planet earth is older than the core. When planet was formed about 4.5 billion years ago, it to be a uniform sphere of warm rock. Radioactive decay and also leftover heat from planetary formation (the collision, accretion, and compression of space rocks) resulted in the ball to get also hotter. Eventually, after around 500 million years, ours young planet’s temperature heated come the melting allude of iron—about 1,538° Celsius (2,800° Fahrenheit). This pivotal minute in Earth’s history is dubbed the stole catastrophe.
The iron catastrophe permitted greater, more rapid motion of Earth’s molten, rocky material. Reasonably buoyant material, such together silicates, water, and even air, stayed close come the planet’s exterior. These materials came to be the early on mantle and crust. Droplets the iron, nickel, and other heavy metals gravitated come the center of Earth, ending up being the early core. This important procedure is called planetary differentiation.
Earth’s main point is the heating system 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 primary contributors to warm in the core room the degeneration of radiation elements, leftover warmth from planetary formation, and also heat released as the liquid external core solidifies close to its boundary through the within core.
Unlike the mineral-rich crust and mantle, the main point is made virtually entirely the metal—specifically, iron and also nickel. The shorthand supplied for the core’s iron-nickel alloys is merely the elements’ chemical symbols—NiFe.
Elements that dissolve in iron, dubbed siderophiles, are also found in the core. Since these elements are uncovered much an ext rarely top top Earth’s crust, numerous siderophiles room classified as “precious metals.” Siderophile facets include gold, platinum, and cobalt.
Another an essential element in Earth’s main point is sulfur—in fact 90% of the sulfur on planet is uncovered in the core. The confirmed discovery of such substantial amounts that sulfur helped explain a geologic mystery: If the core was mainly NiFe, why wasn’t it heavier? Geoscientists speculated the lighter aspects such as oxygen or silicon might have been present. The abundance of sulfur, another reasonably light element, explained the conundrum.
Although we know that the main point is the hottest component of our planet, its precise temperatures are difficult to determine. The fluctuating temperature in the core depend on pressure, the rotation of the Earth, and the varying composition of main point elements. In general, temperatures variety from around 4,400° Celsius (7,952° Fahrenheit) to around 6,000° Celsius (10,800° Fahrenheit).
The main point is made of 2 layers: the outer core, which boundaries the mantle, and also the inside core. The boundary separating these areas is called the Bullen discontinuity.
The outer core, around 2,200 kilometers (1,367 miles) thick, is largely composed of liquid iron and also nickel. The NiFe alloy of the outer core is really hot, between 4,500° and 5,500° Celsius (8,132° and 9,932° Fahrenheit).
The liquid steel of the outer core has really low viscosity, meaning it is easily deformed and also malleable. The is the site of violent convection. The churning metal of the external core creates and also sustains Earth’s magnetic field.
The hottest part of the main point is in reality the Bullen discontinuity, wherein temperatures with 6,000° Celsius (10,800° Fahrenheit)—as hot as the surface of the sun.
The inner core is a hot, thick ball of (mostly) iron. It has actually a radius of around 1,220 kilometers (758 miles). Temperature in the inner core is around 5,200° Celsius (9,392° Fahrenheit). The press is nearly 3.6 million setting (atm).
The temperature that the inner core is far over the melting allude of iron. However, uneven the outer core, the inner main point is no liquid or also molten. The within core’s intense pressure—the whole rest the the planet and also its atmosphere—prevents the iron native melting. The pressure and also density are simply too good for the iron atoms to move right into a liquid state. Because of this unusual collection of circumstances, some geophysicists like to interpret the inner main point not together a solid, but as a plasma behaving together a solid.
The liquid external core separates the inner core from the rest of the Earth, and also as a result, the inner main point rotates a tiny differently than the rest of the planet. The rotates eastward, choose the surface, but it’s a tiny faster, do an extra rotation around every 1,000 years.
Geoscientists think that the iron crystals in the inside core are arranged in one “hcp” (hexagonal close-packed) pattern. The crystals align north-south, along with Earth’s axis of rotation and magnetic field.
The orientation the the decision structure way that seismic waves—the many reliable means 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 with the Equator.
As the entire earth slowly cools, the inner main point grows by around a millimeter every year. The inner core grows as bits that the liquid external core solidify or crystallize. One more word for this is “freezing,” back it’s crucial to remember the iron’s freezing point an ext than 1,000° Celsius (1,832° Fahrenheit).
The development of the inner core is not uniform. It occurs in lumps and bunches, and also is influenced by activity in the mantle.
Growth is much more concentrated roughly subduction zones—regions whereby tectonic plates space slipping from the lithosphere into the mantle, hundreds of kilometers above the core. Subducted plates attract heat native the core and also cool the neighboring area, causing enhanced instances of solidification.
Growth is less concentrated about “superplumes” or LLSVPs. This ballooning masses the superheated mantle absent likely influence “hot spot” volcanism in the lithosphere, and also contribute to a more liquid external core.
The core will never ever “freeze over.” The crystallization procedure is really slow, and the consistent radioactive degeneration of Earth’s inner slows it also further. Scientists estimate it would take around 91 billion years for the main point to totally solidify—but the sunlight will burn the end in a portion of the time (about 5 exchange rate years).
Just choose the lithosphere, the inner core is split into eastern and also western hemispheres. This hemispheres don’t melt evenly, and also have distinct crystalline structures.
The west hemisphere appears to it is in crystallizing an ext quickly 보다 the eastern hemisphere. In fact, the eastern hemisphere that the within core might actually be melting.
Geoscientists recently discovered that the inner main point itself has a core—the within inner core. This strange attribute differs from the inner core in lot the same way the inner core differs from the outer core. Scientists think the a radical geologic change about 500 million years ago caused this inside inner main point to develop.
The crystals the the inner 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 stole crystals may even have a completely different framework (not hcp), or exist at a various phase.
Earth’s magnetic ar is developed in the swirling outer core. Magnetism in the outer core is around 50 times stronger than it is on the surface.
It can be simple to think the Earth’s magnetism is resulted in by the large ball of solid steel in the middle. However in the within core, the temperature is so high the magnetism of iron is altered. When this temperature, referred to as the Curie point, is reached, the atoms of a substance have the right to no longer align to a magnetic point.
Some geoscientists describe the outer core as Earth’s “geodynamo.” for a earth to have a geodynamo, it have to rotate, the must have actually a fluid medium in its interior, the fluid must have the ability to conduct electricity, and it must have an internal energy supply the drives convection in the liquid.
Variations in rotation, conductivity, and also heat affect the magnetic ar of a geodynamo. Mars, for instance, has actually a completely solid core and also a weak magnetic field. Venus has a fluid core, yet rotates too progressively to churn far-reaching convection currents. It, too, has a weak magnetic field. Jupiter, top top the various other hand, has actually a liquid main point that is constantly swirling as result of the planet’s quick rotation.
Earth is the “Goldilocks” geodynamo. It rotates steadily, at a brisk 1,675 kilometers every hour (1,040 miles every hour) at the Equator. Coriolis forces, one artifact of Earth’s rotation, cause convection currents to it is in spiral. The liquid iron in the external core is wonderful electrical conductor, and creates the electrical currents the drive the magnetic field.
The power supply that drives convection in the external core is listed as droplets of liquid iron frozen onto the heavy inner core. Solidification releases warmth energy. This heat, in turn, provides the continuing to be liquid iron more buoyant. Warmer liquids spiral upward, while cooler solids spiral downward under intense pressure: convection.
Earth’s magnetic ar is an important to life on our planet. It protects the earth from the fee particles of the solar wind. Without the shield that the magnetic field, the solar wind would strip Earth’s atmosphere of the ozone layer that protects life from harmfulultraviolet radiation.
Although Earth’s magnetic ar is normally stable, the fluctuates constantly. As the liquid external core moves, for instance, that can adjust the location of the magnetic North and also South Poles. The magnetic phibìc Pole moves up to 64 kilometers (40 miles) every year.
Fluctuations in the main point can cause Earth’s magnetic field to change even more dramatically. Geomagnetic pole reversals, for instance, happen around every 200,000 come 300,000 years. Geomagnetic pole reversals are simply what they sound like: a adjust in the planet’s magnetic poles, so the the magnetic North and South Poles are reversed. This “pole flips” space not catastrophic—scientists have listed no real changes in tree or animal life, glacial activity, or volcano eruptions throughout previous geomagnetic pole reversals.
Geoscientists cannot research the main point directly. Every information around the core has actually come from sophisticated reading the seismic data, evaluation of meteorites, laboratory experiments through temperature and pressure, and computer modeling.
Most main point research has been carried out by measure up seismic waves, the shock waves released by earthquakes at or near the surface. The velocity and also frequency the seismic body waves alters with pressure, temperature, and rock composition.
In fact, seismic waves aided geoscientists determine the structure of the core itself. In the so late 19th century, scientists noted a “shadow zone” deep in the Earth, wherein a type of human body wave dubbed an s-wave either stopped completely or to be altered. S-waves space unable come transmit with fluids or gases. The suddenly “shadow” where s-waves disappeared indicated that earth had a fluid layer.
In the 20th century, geoscientists discovered an increase in the velocity the p-waves, another kind of human body wave, at about 5,150 kilometers (3,200 miles) below the surface. The boost in velocity synchronized to a readjust from a fluid or molten tool to a solid. This verified the existence of a solid inner core.
Meteorites, space rocks the crash to Earth, also administer clues around Earth’s core. Many meteorites are fragments of asteroids, rocky bodies the orbit the sun in between Mars and Jupiter. Asteroids formed about the same time, and from around the exact same material, as Earth. By examining iron-rich chondrite meteorites, geoscientists can acquire a peek into the early formation of our solar system and also Earth’s early on core.
In the lab, the most valuable tool for studying forces and also reactions in ~ the main point is the diamond anvil cell. Diamond anvil cells usage the hardest problem on planet (diamonds) to simulate the very high pressure at the core. The an equipment uses one x-ray laser come simulate the core’s temperature. The laser is beamed with two diamonds squeezing a sample in between them.
Complex computer system modeling has actually also allowed scientists to research the core. In the 1990s, for instance, modeling beautifully portrayed the geodynamo—complete v pole flips.

Although the inner core is mainly NiFe, the iron catastrophe additionally drove heavy siderophile elements to the facility of the Earth. In fact, one geoscientist calculated the there are 1.6 quadrillion lots of gold in the core—that’s sufficient to gild the entire surface that the planet half-a-meter (1.5 feet) thick.
One that the many bizarre methods geoscientists research the main point is v “geoneutrinos.” Geoneutrinos room neutrinos, the lightest subatomic particle, released by the organic radioactive degeneration of potassium, thorium, and uranium in Earth’s interior. By researching geoneutrinos, researchers can better understand the composition and spatial distribution of materials in the mantle and also core.
“Subterranean fiction” defines adventure stories ensuing deep listed below the surface ar of the Earth. Jules Verne’s Journey come the center of the Earth is most likely the most well-known piece of subterranean fiction. Other examples incorporate Dante Alighieri’s Divine Comedy, in i beg your pardon the deepest facility of earth is Hell itself; the movie Ice Age: Dawn of the Dinosaurs, in i m sorry an underground world allows dinosaurs come survive into the present day; and also the hare hole the Alice’s Adventures in Wonderland—which was initially titled Alice’s Adventures Under Ground.
Inge Lehman, who dubbed herself “the just Danish seismologist” functioning in the 1930s, to be a pioneering figure in the research of Earth’s interior. Lehman was the an initial to recognize Earth’s solid inner core, and became a leading expert in the structure of the top mantle together well. She to be the first woman to obtain the prestigious william Bowie Medal, the highest honor vested by the American Geophysical Union. In 1997, the AGU produced the Inge Lehman Medal, recognizing a scientist’s “outstanding contributions to the knowledge of the structure, composition, and also dynamics of the Earth"s mantle and also core.”

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

process of researching a trouble or situation, identify its characteristics and also how they space related.

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

(atm) unit of measurement same to air pressure at sea level, around 14.7 pounds every square inch. Also called traditional atmospheric pressure.

type the mineral the is clean and, once viewed under a microscope, has a repeating sample of atoms and molecules.

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

the suddenly shaking the Earth"s crust brought about by the relax of power along error lines or from volcanic activity.

temperature in ~ which liquid becomes solid; the freezing suggest of water is 0 degrees Celsius (32 degrees Fahrenheit).

change in a celestial body"s magnetic field so that the magnetic North and also South Poles are switched.

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

intensely hot region deep in ~ the earth that rises to simply underneath the surface. Some hot spots develop volcanoes.

oddly crystallized framework at the love of our planet, with iron crystals oriented east-west instead of north-south (as with the within core).

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

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

(large low shear velocity province) seismically anomalous an ar at the deepest part of Earth"s mantle. Also called a superplume or thermo-chemical pile.

able to develop a force ar that can tempt or repel certain substances, usually metals (magnets).

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

seismic shock tide that to represent longitudinal motion. Also called a primary wave or pressure wave.

transformation the an unstable atomic nucleus right into a lighter one, in i m sorry radiation is exit in the form of alpha particles, beta particles, gamma rays, and also other particles. Likewise called radioactivity.

flow of charged particles, largely protons and electrons, indigenous 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 solid rock consisted of of Earth"s lithosphere (crust and also upper mantle). Also called lithospheric plate.

powerful irradiate waves that are too quick for people to see, but can penetrate Earth"s atmosphere. Ultraviolet is frequently shortened to UV.

See more: Who I Mained What I Played What I Expected What I Got Template

upward activity of molten product from within the planet to the surface, whereby it cools and hardens.


join our ar of educators and receive the latest info on national Geographic"s resources for you and your students.

Educational sources in your Inbox

sign up with our community of educators and also receive the latest information on national Geographic"s resources for you and also your students.