Delbridge, Brent G. Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts.
Ishii, Miaki Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts.
Last reviewed:February 2018
Show previous versions
- Discovery and challenges
- Core evolution and magnetic field
- Links to Primary Literature
- Additional Readings
The dense kernel of Earth comprised primarily of iron and nickel that contains nearly one-third of the mass of the planet. Three distinct compositional spheres make up the Earth’s interior: the core, mantle, and crust (Fig. 1). A model of the Earth’s interior, constructed using seismic data and theoretical consideration of mineral physics, as well as the Earth’s mass and moment of inertia, shows the core–mantle boundary at about 2900 km below the surface of the Earth, at 3400-km radius (Fig. 1). The metallic core lies beneath the rocky shells of the crust and mantle and is composed largely of iron and nickel, accompanied by some lighter elements (such as silicon, oxygen, sulfur, hydrogen, and carbon). Because of the sensitivity of the melting temperatures of iron–nickel alloys on pressure, namely, that the melting point of iron increases more rapidly with pressure than with temperature, the core is further divided into two distinct regions: a solid inner core where the temperature is below the melting point and a liquid outer core where the temperature exceeds the melting point (Fig. 2). Pressure within the core is nearly hydrostatic, increasing from about 135 gigapascals (GPa) at the core–mantle boundary to 365 GPa at the center of the Earth. See also: Hydrostatics; Earth's interior
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information