The Structure and Composition of the Earth

The Earth has three main layers:

  • Crust
  • Mantle
  • Core

Starting from the outermost layer, the Earth is composed of the crust, followed by the mantle, and finally the core.

Earth’s Layers

The crust

The Earth’s crust is the thinnest of the three layers, and it is the solid surface where we stand and live. This rocky layer is divided into many huge pieces of land called tectonic plates. The movement of these tectonic plates is responsible for many geological activities, such as earthquakes, volcanic eruptions, and the formation of mountain ranges.

However, the thickness of the crust varies depending on location. In some areas, it is very thick, while in other areas it is very thin. We live on the thicker areas of crust, known as continental crust, which are higher ground. The ocean has a thinner type of crust known as oceanic crust, which is typically covered by water and thinner than continental crust. The thinner areas of the crust can cause problems like earthquakes.

The two types of crust are very different from each other and are made up of different minerals and rocks. Continental crust is usually thicker and less dense than oceanic crust. On average, continental crust is around 35 to 40 km thick, while oceanic crust is typically around 5 to 10 km thick.

Also, continental crust is generally older than oceanic crust, with some areas of continental crust being more than 4 billion years old. Whereas, most oceanic crust is 200 million years old or younger.

The mantle

The Earth’s mantle is the thickest of the three layers. It is made of mostly solid rock and has the properties of a solid, however, it can also flow beneath the crust. Very slowly, the hot rock rises and the cooler rock falls, which is due to convection currents.

The core

The centre of the Earth is called the core, which is divided into the inner core and the outer core.

  • The outer core is made from liquid iron and nickel
  • The inner core is solid

Both iron and nickel are magnetic, which generates the Earth’s magnetic field.

Elements Larger than Iron

On the periodic table below, the element circle is iron (Fe).

While iron is a common element on Earth, we have also discovered elements that are heavier than iron. This suggests that Earth was formed from the explosion of a supernova.

A supernova is a massive star that explodes and sends heavy elements like iron and heavier elements into space. This eventually formed our planet. Elements heavier than iron only form during supernova explosions.