The Primary Layers of Earth
During Earth’s early formation, our planet went through a differentiation span, which led to the heaviest elements sinking to the center. At the same time, the lighter materials moved to the surface. The internal layering of the Earth can be, hence, defined as per the resulting chemical composition. After studying the Earth and its composition over the decades, scientists have made it clear that our planet comprises three main layers.
They are the crust, mantle, and core. All of us humans and the Earth’s wildlife and fauna live on the crust, the solid outer layer of Earth. The mantle is located below the crust, and at the bottom lies the core.
The Crust of the Earth
The most buoyant and lightest rock layer of the Earth is the crust. While the continental crust covers 41% of our planet’s surface, the oceanic crust covers its remainder. The continental crust is around 20 to 80 km thick, and a quarter of its area is beneath the oceans. The rocks here are more than four billion years old. The oceanic crust is young and not more than 170 million years old. Its thickness is just 8 kilometres.
It stands lower than the continental crust, which goes deep into the Earth’s mantle. Although the upper continental crust gets exposed in many regions, its composition is yet to be known. The lower continental crust remains unexposed, and geologists use human-made explosions and shockwaves from earthquakes to study and pass across it. The rare fragments that move to the surface after a volcanic eruption are also studied closely.
The Mantle of the Earth
The mantle lies under the Earth’s crust and is composed of hot magma and other semi-solid minerals and rocks. Tectonic activities in the mantle frequently lead to visible changes in the Earth’s crust. It includes earthquakes as well as volcanic eruptions. The mostly solid bulk present in the interior of our Earth is the mantle. It makes up a massive 84 percent of the Earth’s total volume and is around 1,802 miles (2,900 kilometres) thick.
The transfer of material and heat in this layer helps determine the landscape of our planet. Plate tectonics is driven by the activities in the mantle, which then contribute to seafloor spreading, mountain-building or orogeny, earthquakes, and volcanoes. This layer of Earth is divided into numerous layers: (i.) the upper mantle, (ii.) the transition zone, (iii.) and D double-prime (D”), which is a strange area where the mantle comes in contact with the outer core.
The Core of the Earth
The core is located right below the mantle of the Earth. It is the hottest and the deepest layer. It is divided into two layers: the outer core and the inner core. It might be tough to imagine, but scientists believe that the Earth’s core has metals that are always moving. As per some scientists, this constant motion makes the inner core rotate faster than the rest of our planet. Movements taking place in the liquid outer core sometimes change the magnetic South and North Poles of the Earth.
The Inner Core
The inner core is shaped like a ball and mostly consists of metal. It is approximately 750 miles in thickness and primarily constitutes iron. For the most part, it is solid, as opposed to the outer core. Even though the iron present in the inner core is hotter than the outer core, the iron does not melt due to the high intensity of pressure from the rest of the Earth.
The iron here can be of 10,000º F or even more, making it as boiling as the Sun’s surface! Thanks to the enormous ball of solid metals as the core, the entire Earth is magnetic. When our planet was formed some billion years back, all its heaviest materials sank to the middle of our developing planet. The less dense and lighter substances remained close to the crust. It is why certain heaviest substances on Earth make up the inner core. (See Why Do Earthworms Come Out in the Rain?)
The Outer Core
Around 1,400 miles in thickness, the Earth’s outer core mostly comprises a combination or an alloy of nickel and iron and little quantities of some other dense elements such as uranium, gold, and platinum. Of course, you can find these metals in their solid form on our planet’s surface. However, they are present in a scorching liquid form in the Earth’s outer core.
It can be as hot as 7,000-9,000º F! As per scientists, the powerful magnetic field of the Earth is controlled by its liquid outer cord. The magnetic field safeguards us from every kind of charged particle floating in the solar system. It includes various harmful rays of the Sun.