Sisäydin

Sisäydin, also known as the inner core, is the innermost layer of the Earth, located approximately 5,150 kilometers (3,200 miles) below the surface. It is primarily composed of iron and nickel, with a density estimated to be around 12.9-13.1 grams per cubic centimeter. The inner core is solid due to the immense pressure exerted by the layers above it, which can reach up to 3.6 million atmospheres at the core-mantle boundary.

The inner core was first proposed by Inge Lehmann in 1936 based on seismic wave observations. It is believed to have a radius of about 1,220 kilometers (760 miles) and a temperature ranging from 5,400 to 6,000 degrees Celsius (9,750 to 10,830 degrees Fahrenheit). The inner core is thought to rotate slightly faster than the rest of the Earth, a phenomenon known as superrotation.

The inner core's existence and properties are inferred from seismic data, as direct observation is currently impossible. The study of the inner core is crucial for understanding the Earth's magnetic field, which is generated by the motion of molten iron in the outer core. The inner core's solidification process also plays a role in the Earth's thermal evolution and the dynamics of the mantle.