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Gravity at different internal layers of Earth (1 = continental crust, 2 = oceanic crust, 3 = upper mantle, 4 = lower mantle, 5+6 = core, A = crust-mantle boundary) Earth's radial density distribution according to the Preliminary Reference Earth Model (PREM). [13] Earth's gravity according to the Preliminary Reference Earth Model (PREM). [13]
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. [1] [2] There are no samples of the core accessible for direct measurement, as there are for Earth's mantle. [3]
Earth's outer core is a fluid layer about 2,260 km (1,400 mi) in height (i.e. distance from the highest point to the lowest point at the edge of the inner core) [36% of the Earth's radius, 15.6% of the volume] and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [31]
Researchers are still discovering more about the Earth's center. A team at Australian National University (ANU) has found evidence of a new layer to the planet sitting within the inner core.
In his 1942 publication of his model, the entire lower mantle was the D layer. In 1949, Bullen found his 'D' layer to actually be two different layers. The upper part of the D layer, about 1,800 km thick, was renamed D′ (D prime) and the lower part (the bottom 200 km) was named D″. [4] Later it was found that D" is non-spherical. [5]
For example, the Earth's mean specific gravity (5.515) is far higher than the typical specific gravity of rocks at the surface (2.7–3.3), implying that the deeper material is denser. This is also implied by its low moment of inertia ( 0.33 M R 2 , compared to 0.4 M R 2 for a sphere of constant density).
The rotation axis of Earth is centered and vertical. The dense clusters of lines are within Earth's core. Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun.
The precise strength of Earth's gravity varies with location. The agreed-upon value for standard gravity is 9.80665 m/s 2 (32.1740 ft/s 2 ) by definition. [ 4 ] This quantity is denoted variously as g n , g e (though this sometimes means the normal gravity at the equator, 9.7803267715 m/s 2 (32.087686258 ft/s 2 )), [ 5 ] g 0 , or simply g ...