In the structure of planet Earth, below the mantle, the core is mainly made up of which one of the following ?

The Earth’s core is predominantly metallic, composed mainly of iron with a significant admixture of nickel (commonly referred to as the “NiFe” layer). Seismological studies that reveal the core–mantle boundary and differing wave behaviours first identified a heavy metallic core, and meteorite compositions support an iron‑rich central region [1]. The outer core is a liquid layer of molten iron–nickel with some lighter elements, while the inner core is a dense solid of similar composition; these properties explain the core’s high density and its role in generating Earth’s magnetic field [2]. Thus, iron is the primary constituent of Earth’s core, with nickel and lighter elements present in smaller amounts.

Sources

1. [1] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 3: Interior of the Earth > The Core > p. 23
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 4: Earths Interior > The Outer Core > p. 55