Understanding Earths Core

It should be noted that many of what are considered to be facts about the earth’s core are actually educated guesses. Man has not reached anywhere near the core, so a lot of the facts are interpolations rather than concrete. Despite this, there are many things that scientists in general are reasonably certain of.


The core is thought to be composed primarily of nickel and iron. These substances are dense and they are good conductors of electrical energy. This not only helps explain Earth’s mass, it is also a reason for the magnetic field that surrounds the planet. Without the magnetic field, it is likely that life, as we know it, could not exist. The magnetic field helps to protect the globe from many of the more dangerous particles and energy that the sun emits. 

Inner and outer core

The core is thought to consist of two distinct layers: The inner core and the outer core. The inner cord, though it is tremendously hot, well above the melting point for either nickel or iron, it is also under such enormous pressure from the weight of the mantle and crust above it that it is solid. This is quite important in creating the magnetic field, as will be seen.

The outer core is also under a great deal of pressure, however it is liquid. The liquid isn’t of the form of a fluid like water, but more like cooking pudding or taffy. Still, it is able to flow, and does so around the inner core, spurred on by the rotation of the earth, in part.

Magnetic dynamo

The rotation of the outer core around the inner core produces massive electrical currents, very much like an electrical generator inside of a hydro-generating dam. For some time, scientists have known of the connection between electricity and magnetism. Therefore, it doesn’t take a great deal of guesswork to determine that Earth’s life protecting magnetic field is generated by the dynamo effect of the outer core’s rotation around the inner core.

Core thickness

Since the density of both nickle and iron are known, as is the approximate weight of the earth, the size of the core has been deduced to be about 3500 km in diameter. It is believed that the outer core is 2300 km in thickness while the inner core is 1200 km in thickness. If the diameter was greater, the earth should weigh more than it does, while if it was much smaller, it should weigh less. However, there is still considerable room for error, either way, and different sources tend to use different thickness figures. Likewise, thought it is known that the temperature is great, probably over 6,000 degrees F. (over 7,000 degrees C.), there are no exact figures. 

Studies continue in an effort to learn more about the earth’s core. What is known so far is fascinating for many reasons. What isn’t known yet is enough to have many scientists eagerly trying to figure out new ways to answer the many questions they don’t yet have answers to, and to continually come up with new questions.