Earth's Crust

We explain what the Earth's crust is, how it was formed, its layers and other characteristics. Also, oceanic and continental crust.

earth crust
The Earth's crust is the only part of the planet that we know directly.

What is the earth's crust?

the earth's crust It is the most superficial layer of planet Earth. It is the outermost, thinnest and most recent of the Earth's layers. It is the layer on which we live living beings, even those that enter the deepest layers of the soil.

The Earth's crust is part, along with the Earth's mantle and the Earth's core, of the so-called geosphere, which is the solid part of the planet. The crust extends from the surface to an average depth of 35 kilometers. The depth is taken as an average since it varies depending on whether it is:

  • Oceanic crust It covers 55% of the planet's surface, located thousands of meters deep under the ocean, and is thinner than the continental surface (with a thickness of 5 km on the ocean floor).
  • continental crust Heterogeneous in nature, since it is made up of rocks of different origins, the most abundant minerals being quartz, feldspars and micas. Its thickness is much greater, reaching 70 km in mountainous areas.

The Earth is the only known rocky planet that has a heterogeneous crust from a chemical and physical point of view, since they were produced by different geological processes.

You may be interested:  Geotechnics

See also: Geomorphology

Characteristics of the earth's crust

layers of the earth crust percentage
The Earth's crust is only 1% of the Earth's total volume.

the earth's crust represents less than 1% of the total volume of the planet. However, it is all we know directly, since extends up to 35 kilometers towards the core, of which only 12.2 km were excavated with the deepest well in history, the Kola Superdeep Well (KSDB), a work of the former Soviet Union.

The bark is the top of the lithosphere along with the upper part of the mantle, above the Mohorovicic discontinuity. Because it is much less dense than the mantle, the crust “floats” on top.

As the depth increases, the temperature also rises, oscillating between 200 and 400 °C, at a rate of 30 °C per kilometer of depth.

The most abundant chemical elements in the composition of the bark are: oxygen (46.6%), silicon (27.7%), aluminum (8.1%), iron (5.0%), calcium (3.6%). %), sodium (2.8%), potassium (2.6%) and magnesium (1.5%). The rest of the volume of the crust is represented by water and other scarce elements, adding up to less than 1% of its composition.

Formation of the earth's crust

In the geological history of the planet, the first earth's crust formed 4.4 to 4.55 billion years ago. Since then its volumes have been increasing over time.

As terrestrial conditions stabilized and the planet cooled, new layers of crust emerged to occupy a considerable volume 2.5 billion years ago, largely thanks to two major geological events: one 2.5-2.7 billion years ago , and another 1700-1900 million years ago.

However, the earth's crust is constantly forming. To do this, portions of it sink into the mantle (subduction) to melt into the underground liquid magma, while other new portions emerge in the expansion centers of the oceanic crust.

You may be interested:  Natural Region

The continental crust has an average age of 2 million years which makes it much older than the oceanic crust.

Movement and dynamics of the Earth's crust

dynamic earth crust
Although we do not perceive it, the cortex is in motion.

The Earth's crust is far from static. The plates that make it up are floating on the mantle composed of pasty materials subjected to enormous pressures. Therefore, a slow displacement of the crust occurs, which is known as tectonic dynamics.

Thus, the different portions of the cortex rub and collide, exerting pressure on each other and giving rise to the orogenesis or creation of mountains, as the crust folds and bulges. In this way the relief depends largely on the movement of the crust.

Similarly, depressions or tectonic faults can also be generated, when one plate submerges below the other, liquefying and increasing the internal pressure of the magma to come out. This is how volcanoes arise.

These movements of the earth's crust also give rise to earthquakes and tremors since the friction between tectonic plates produces seismic waves that are transmitted to the surface, sometimes with devastating effects.

In the same way, cause continental drift which is the movement of continental masses over time, from primitive supercontinents (such as Pangea) to the current configuration.

Layers of the earth's crust

The Earth's crust is a relatively homogeneous layer, that is, it has no layers or subdivisions. The only way to differentiate it is between the continental crust, which is thicker, older and more robust, and the oceanic crust, which is younger, thinner and more mobile.

Importance of the earth's crust

The Earth's crust is a vital area of ​​the planet. For a start, that's where life takes place (biosphere), unique phenomenon of our planet in the Solar System.

You may be interested:  Climates of Mexico

Also at this point the dry and warm rocks can react with the water and oxygen that abound on the surface. New forms of rocks and minerals emerge in the crust that make up the mineral wealth and abundance of our environment.

Besides, orogenesis would not be possible without crustal movements nor the complex dynamics of geological changes that this implies, and therefore chemical cycles such as that of water could not occur, which requires mountains to flow in rivers towards the sea.

References

  • “Earth's crust” in Wikipedia.
  • “Earth's crust” in Enciclopedia.us.
  • “Crust” in National Geographic.
  • “Earth's crust” in The Encyclopaedia Britannica.