What is the Earth’s Crust: Definition for Kids

First of all, we must know the structure of our planet. It is made up of four concentric layers :

• Inner core.
• External nucleus.
• Mantle.
• Cortex.

These layers are different from each other due to their composition, characteristics and properties. In this way, the inner core corresponds to the center of the earth and the rest of the layers are arranged over it, until reaching the earth’s crust , which is the outermost layer .

Definition of Earth’s crust

Therefore, the earth ‘s crust , is a kind of r evestimiento that envelops the entire surface of the planet , providing a solid foundation on which we walk ourselves and upon which they are based, deserts, forests, fields and oceans.

It is mainly made up of rocks of different natures (igneous, metamorphic and sedimentary) and its thickness varies from 5 km at sea level, to 70 km deep in relief areas and mountains.

In addition, the crust is not a uniform layer , but is divided into parts called plates, which are in a state of permanent floating , that is, they “float” on the innermost layers of the earth, moving very slowly and in a constant manner. almost imperceptible way for the human being. However, on some occasions, more abrupt movements occur, which give rise to earthquakes or volcanic eruptions , due to the heat and energy given off in the center of the earth, which causes the plates to move or collide with each other.

Thus, the earth’s crust is not unique, but there are two types of earth’s crust:

• The oceanic crust , which covers the part of the planet on which the oceans are deposited, giving rise to the seabed.
• The continental crust that covers the rest of the earth’s surface.

Below we explain the characteristics of each of them.

The oceanic crust occupies approximately 60% of the Earth’s surface and is composed, for the most part, of rocks of volcanic origin and dark color, such as basalts and gabbros, ranging in thickness between 5 and 10 km.

Contrary to what was believed in the past, the oceanic crust, like the continental one, can present reliefs and geographical features , thus existing plains, mountains, cracks and underwater volcanoes. In fact, the oceanic crust does not begin on the coast, but several kilometers from it, marked by a steep slope or slope.

In addition, oceanic plates are much younger than continental ones due to the renewal process to which they are subjected. This process consists in that, due to the movement of the plates, they can be separated by causing the molten material of the earth’s interior to rise and deposit on the oldest layers, or, instead of separating, the plates are superimposed on each other. causing the subsidence of older materials.

The continental crust occupies 40% of the earth’s surface and is made up of rocks of different origins, although the majority is made up of metamorphic rocks such as granite and covered by sedimentary rocks such as limestone, sandstone or clay. Its thickness varies between 30 km in the plains and 70 km in the highest mountains.

In it are a variety of reliefs and geographical features, caused by the movement of the plates . There are areas that, on the contrary, have not suffered any kind of fragmentation or deformation in a long time, called cratons. The cratons , are usually found inside continents, constituting the oldest and most stable part of the Earth ‘s crust and are divided into :

• Shields : when the craton appears on the surface.
• Platform : when the craton is buried under sediment.

The continental crust is usually much older than the oceanic crust, because it is not subjected to any recycling or renewal process, some of the sections being practically as old as the origin of the Earth.