What is the Earth Made Of?

The Earth with all its unique features is truly a wonderful place to be. Our 4.6 billion years (age debated) old planet Earth that we live on has a surface area of 197 million square miles, of which about 70 percent of the Earth's surface is covered with water. The mass of the Earth is 5.97 x 10²⁴ kg and density is 5.5 g/cm³. This density makes the Earth the densest planet in the solar system. The Earth we live on actually consists of 32% iron, 30% oxygen, 15% silicon, 14% magnesium and other elements like nickel, sulfur, calcium, aluminum, etc. To understand what the Earth is made of, we need to divide the earth up into convenient elements or piles. Let's have a detailed look.

Composition of the Earth

The Earth can be divided into three main levels: crust, mantle and core, as we move from the outer regions of the Earth towards the interior.

Crust
The outer shell enveloping the earth is called the crust, which varies in depth from 5 - 75km and comprises mainly silicates and oxygen. It is this crust that we come in direct contact with normally. It's the surface on which we are living. The crust is thinner than the other layers of the earth, however, its thickness varies from one region to another. Depending on this thickness, there are two kinds of crust: Oceanic crust and Continental crust.

Oceanic crust refers to the crust below oceans and is 6 - 11km thick, comprising mainly heavy rocks such as basalt. Oceanic crust forms the thinnest part of the crust. Continental crust refers to the crust under continents and is about 30 km thick. It mainly comprises light material called granite. As such, the crust has no influence of the earth, however, its constant moving does. Convection currents cause the earth plates to move, which when touch other conduce to earthquakes.

Mantle
Beneath the thin earth's crust lies the mantle, which is nothing but molten rock. The mantle forms the largest portion of the Earth's volume, however, it's not visible to us normally. It's only when cracks in the crust take place, that molten rock is allowed to seep out. This is mostly seen in the case of volcanoes. This mantle mainly comprises silicate rocks rich in magnesium and iron. The upper mantle flows more easily than the lower mantle due to the increasing temperature and pressures seen as one descends into the earth.

The Earth's tectonic plates float on this mantle. The mantle actually features convection process. The hotter materials of the mantle heated by the core of the Earth gradually rise to the mantle's surface. This material then cools near the crust and again sinks to the core, where it attains high temperature again and rises up. This process continues and is believed to be the spearheading force of the Earth's tectonic plates.

Core
The Earth's core lies beyond the mantle and can be again divided into a liquid outer core (radius of 1,220 km) and a solid inner core (radius of 1,220 km). It is this core that protects us from the harmful radiations of space. The core in all comprises 80% iron, some nickel and gold, platinum and uranium as well. The outer core mainly consists of the nickel-iron alloy, while the solid inner core mostly comprises iron. The reason the inner core is solid is attributed to significantly high pressure prevalent at the core. The pressure towards the outer core is lower, which is why the outer core is liquid.

Some interesting facts about the Earth we live on are that the deepest places on the Earth are in South Africa, wherein, mining companies have managed to excavate 3.5 km into the earth to extract gold. Besides the South African miners, nobody has dug deeper into the Earth's crust. Moreover, besides the three levels we also need to keep in mind the earth's atmosphere; surrounded by atmospheric gases, which all form a major part of the earth. The earth's atmosphere consists of 78% nitrogen, 21% oxygen, 0.93% argon, 0.03% carbon dioxide and 0.04% of other gases. The Earth we live on is simply wonderfully wired and geared.