What is believed to be the main composition of the Earth's core?

The main composition of the Earth's core is primarily believed to be iron. This is based on seismic data, which indicates that the core is composed of a solid inner core and a liquid outer core. The temperature and pressure conditions deep within the Earth favor the presence of iron, which can exist in both solid and liquid states under extreme conditions.

Iron's significance in the core is also supported by the fact that it is one of the most abundant elements in the universe, and its density is sufficient to account for the characteristics observed in the Earth’s overall density and gravitational field. Moreover, the liquid outer core plays a critical role in generating the Earth's magnetic field through the process of convection and the movement of molten iron.

While other elements like silicon, oxygen, and magnesium are present in the Earth's mantle and crust, they do not primarily make up the core. As a result, understanding the core's composition as predominantly iron helps explain not just the physical properties of the core, but also the magnetic phenomena associated with Earth.