What is the primary composition of the inner core?

The primary composition of the inner core is indeed solid iron and nickel. Scientists believe that the inner core, under immense pressure, has solidified despite the extremely high temperatures found there, estimated to be as hot as the surface of the sun. This pressure causes the iron and nickel to stay solid rather than melting into a liquid state, which is the condition that exists in the outer core.

The solid inner core contrasts with the outer core, which is composed of melted iron and nickel and is responsible for generating the Earth’s magnetic field through its fluid movements. Understanding the differences in composition between the inner and outer layers of the Earth's core helps explain various geological phenomena, such as seismic activity and heat flow from the Earth's interior to its surface.