Interesting Facts About Earth’s Core

Using the seismic data, the scientists had first postulated the existence of a fluid core. In 1915, Gutenberg published a measurement of the core’s radius. In 1936, Danish seismologist Inge Lehmann (l888-1993) presented a paper titled, “P'” (or P -Prime, after the seismic waves), which announced the discovery of Earth’s inner core. The division between the inner and outer core is now called the Lehmann discontinuity.

The size of this core was calculated later in 1960s when an underground nuclear test was conducted in Nevada. Because the precise location and time of the explosion was known, echoes from seismic waves bounced off the inner core provided an accurate means of determining its size. These data revealed a radius of Earth’s Inner solid Core about 1,216 kilometers. The seismic P-waves passing though the inner core move faster than those going through the outer core-good evidence that the inner core is solid. The presence of high-density iron thought to make up the inner core also explains the high density of the Earth’s interior, which is about 13.5 times that of water.

Outer Core versus Inner Core

Earth’s core is divided into two parts viz. a solid inner core with a radius of =1,216 km and a liquid outer core extending beyond it to a radius of ~3,400 km. The solid inner core is generally believed to be composed primarily of iron and some nickel.

How it was formed?

The major event which led to the formation of core was iron catastrophe. Earth was formed approximately 4500 million years ago. After accumulation of the Earth’s material into a spherical mass, the material was mostly uniform in composition. The collision of the material which formed the Earth was significant; heating from radioactive materials in this mass further increased the temperature until a critical condition was reached, when the material was molten enough to allow movement. At this point, the denser iron and nickel evenly distributed throughout the mass sank to the centre of the planet to form the core – an important process of planetary differentiation. The gravitational potential energy released by the sinking of the dense Ni-Fe globules increased the temperature of the protoplanet above the melting point resulting in a global silicate magma which accelerated the process. This event occurred at about 500 million years into the formation of the planet and is known as Iron catastrophe.

Recent researches show that the innermost part of the core is enriched in gold, platinum and other Siderophile elements (Siderophile elements are those ‘Iron Loving” elements that tend to bond with metallic iron as per Goldschmidt classification).