innercore
The inner core is the Earth's innermost region, a solid sphere at the planet's center. It has a radius of about 1,200 kilometers, and is surrounded by a liquid outer core that extends to roughly 3,500 kilometers from the center. The boundary between the inner and outer core is known as the inner core boundary. The inner core is primarily composed of iron, with smaller amounts of nickel and light elements such as sulfur, silicon, or oxygen.
Conditions in the inner core are extreme. Pressures at the center are on the order of hundreds
Geophysical evidence for the inner core comes from seismic studies. Inge Lehmann, in 1936, inferred a solid
The inner core grows slowly as the Earth cools, crystallizing from the liquid outer core and releasing