As you might expect, this placemark takes you to a hot, dark place, with a pressure greater than 3.6 million times atmospheric pressure at sea level. In terms of heat and pressure, these conditions far exceed those necessary to create diamonds.


Earth cross section by Keelin Murphy [with National Science Foundation funding through the Center for High Pressure Research (CHiPR)]

The center of the Earth is about 6,378 kilometers beneath the equator and 6,357 kilometers beneath the poles, and lies inside the Earth's core. The core is composed primarily of iron and nickel and smaller amounts of lighter elements, which may include sulfur and oxygen.

The inner core is solid and has a radius of about 1220 kilometers, while the outer core is molten. The upper surface of the outer core is about 2890 kilometers beneath the Earth's surface.


Image from Nevada Seismological Laboratory: Earth's Interior

Evidence for the liquid state of the outer core includes the behavior of seismic waves as they travel through the Earth. While P (primary or compressional) waves can travel through liquid, the S (secondary or shear) waves cannot, and the pattern of arrival of S waves on the Earth's surface after they have traveled through its interior indicates that the outer part of the core is liquid.


Image from Nevada Seismological Laboratory: Earth's Interior

Wikipedia: Inner core

Wikipedia: P-wave

Wikipedia: S-wave

The Consortium for Materials Properties Research in Earth Sciences (COMPRES) is a community-based consortium whose goal is to enable Earth Science researchers to conduct the next generation of high-pressure science on world-class equipment and facilities. It facilitates the operation of beam lines, the development of new technologies for high pressure research, and advocates for science and educational programs to the various funding agencies. The work of COMPRES can help us understand the nature of the materials and phenomena that operate in the Earth's interior.

NSF's Cooperative Studies of the Earth's Deep Interior (CSEDI) program is a Special Emphasis area to support basic research on the character and dynamics of the Earth's mantle and core, their influence on the evolution of the Earth as a whole, and on processes operating within the deep interior that affect or are expressed on the Earth's surface.

Additional information about Cooperative Studies of the Earth's Deep Interior (CSEDI)

USGS: The Interior of the Earth
Wikipedia: Structure of the Earth
School of Geology & Geophysics, University of Oklahoma: Seismology and Earth's Interior