Editor's note : Paul Earle's affiliation has been corrected. He was a graduate student at Scripps Institute of Oceanography. The story has also been updated to show that Song and Richards were the first to provide seismic evidence of inner core super-rotation.
Share Tweet Email. Read This Next Wild parakeets have taken a liking to London. Animals Wild Cities Wild parakeets have taken a liking to London Love them or hate them, there's no denying their growing numbers have added an explosion of color to the city's streets. India bets its energy future on solar—in ways both small and big. Environment Planet Possible India bets its energy future on solar—in ways both small and big Grassroots efforts are bringing solar panels to rural villages without electricity, while massive solar arrays are being built across the country.
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Go Further. Animals Wild Cities This wild African cat has adapted to life in a big city. Animals This frog mysteriously re-evolved a full set of teeth. Animals Wild Cities Wild parakeets have taken a liking to London. Animals Wild Cities Morocco has 3 million stray dogs. Meet the people trying to help. Fortunately, the reader need not worry: let's see why. First things first, let's establish the facts. The diagram below shows the interior structure of the Earth as a whole. Right now, the Earth's core has both solid and liquid components, which respectively make up the inner and outer core shown in light and dark grey.
When the Earth formed, it would have been entirely molten due to the release of gravitational energy; at this time, the Earth became chemically differentiated , meaning that heavy elements notably iron mostly sank to the center to form the core while relatively light elements remained in the mantle and crust. The energy released by the formation and differentiation of the Earth is often called primordial heat. It turns out that, if primordial heat had been all the Earth had to work with, the core would have completely solidified long ago, which is inconsistent with observation.
As the question suggests, something else must provide additional heat to slow the solidification of the core; this alternative heat source so happens to be radioactivity.
As we noted before, heavy elements mostly ended up in the Earth's core. One might think, therefore, that the core contains most of the Earth's budget of radioactive substances.
It turns out, however, the most important radioactive species on Earth -- uranium and , thorium, and potassium -- are lithophilic or 'rock-loving.
As they decay, radioactive atoms release energy as radiogenic heat in the mantle. Much as an electric blanket keeps you warm on a cold winter's night, radiogenic heat has allowed Earth's core to remain hot and molten far longer than primordial heat. Specifically, the timescale for the core to cool and solidify is related to the half-lives of the species that supply radiogenic heat, which range between million and 14 billion years.
The Earth is currently about 4. By the way, don't worry about the radioactivity in Earth's interior -- it is in no way dangerous to you, your loved ones, or your cat. In summary, the Earth's core is cooling very, very slowly; some of it has solidified, but it will take many billions of years for the rest to follow suit. Correction: An earlier version of this article stated that most of the Earth's radioactive elements were in the core rather than the mantle. Citation : Probing Question: What heats the earth's core?
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E-mail the story Probing Question: What heats the earth's core? Your friend's email. Your email. I would like to subscribe to Science X Newsletter. Learn more. It, too, has a weak magnetic field. It rotates steadily, at a brisk 1, kilometers per hour 1, miles per hour at the Equator. The liquid iron in the outer core is an excellent electrical conductor, and creates the electrical current s that drive the magnetic field.
The energy supply that drives convection in the outer core is provided as droplets of liquid iron freeze onto the solid inner core. Solidification releases heat energy. This heat, in turn, makes the remaining liquid iron more buoyant. Warmer liquids spiral upward, while cooler solids spiral downward under intense pressure: convection.
It protects the planet from the charged particles of the solar wind. As the liquid outer core moves, for instance, it can change the location of the magnetic North and South Poles. The magnetic North Pole moves up to 64 kilometers 40 miles every year. Geomagnetic pole reversal s, for instance, happen about every , to , years. Geoscientists cannot study the core directly.
All information about the core has come from sophisticated reading of seismic data, analysis of meteorites, lab experiments with temperature and pressure, and computer modeling. Most core research has been conducted by measuring seismic waves, the shock wave s released by earthquake s at or near the surface.
The velocity and frequency of seismic body waves changes with pressure, temperature, and rock composition. In fact, seismic waves helped geoscientists identify the structure of the core itself. S-waves are unable to transmit through fluids or gases. In the 20th century, geoscientists discovered an increase in the velocity of p-wave s, another type of body wave, at about 5, kilometers 3, miles below the surface.
The increase in velocity corresponded to a change from a liquid or molten medium to a solid. This proved the existence of a solid inner core. Most meteorites are fragments of asteroid s, rocky bodies that orbit the sun between Mars and Jupiter. Asteroids formed about the same time, and from about the same material, as Earth. In the lab, the most valuable tool for studying forces and reactions at the core is the diamond anvil cell.
Diamond anvil cells use the hardest substance on Earth diamonds to simulate the incredibly high pressure at the core. The laser is beamed through two diamonds squeezing a sample between them. Complex computer modeling has also allowed scientists to study the core. In the s, for instance, modeling beautifully illustrated the geodynamo—complete with pole flips.
The core is the hottest, densest part of the Earth. Illustration by Chuck Carter. Buried Treasure. Although the inner core is mostly NiFe, the iron catastrophe also drove heavy siderophile elements to the center of the Earth. In fact, one geoscientist calculated that there are 1. By studying geoneutrinos, scientists can better understand the composition and spatial distribution of materials in the mantle and core.
Subterranean Fiction.
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