EARTH'S CRUST: CHARACTERISTICS, TYPES, STRUCTURE, COMPOSITION - GEOGRAPHY - 2025

The Earth's crust is the most superficial layer of planet Earth and is the scene in which life develops. Earth is the third planetary star in the solar system, and more than 70% of its surface is filled with oceans, seas, lakes and rivers.

Since the formation of the earth's crust began, it has undergone tremendous transformations as a result of cataclysms, floods, glaciations, meteor strikes and other factors that have made it what we see today.

The Earth's crust is the most superficial layer of the planet. Source: Vectorized and translated from the English version by Jeremy Kemp. Based on elements of an illustration by USGS.

The depth of the earth's crust ranges from 5 kilometers to 70 kilometers at its highest point. There are two types of crust: oceanic and terrestrial. The first is the one that is covered by the watery masses that make up the great oceans and seas.

Related concepts

This blue planet where all the conditions required for life to proliferate have been met, since it broke into the solar system a little over four and a half billion years ago, has undergone transformations that have finally led to what it is today.

If we take into account that the estimated age of the universe since the Big Bang is set at a little more than thirteen billion years in the past, the formation of our planetary house began towards the end of the second third of creation.

It was a slow, turbulent and chaotic process that only about a hundred thousand years ago managed to emerge as the planet Earth we know today. The Earth showed its full potential only after complex processes that purified the atmosphere and regulated the temperature to bring it to levels tolerable by the first primitive forms of life.

As a living being, the planet is changeable and dynamic, so its violent shaking and natural phenomena are still surprising. The geological study of its structure and composition has made it possible to know and outline the different layers that make up the planet: the core, the mantle and the earth's crust.

Core

It is the innermost area of ​​the planetary sphere, which in turn is divided into two: outer core and inner or inner core. The inner core occupies an approximate radius of 1,250 kilometers and is located in the center of the planetary sphere.

Studies based on seismology show evidence that the inner core is solid and is basically composed of iron and nickel - extremely heavy minerals - and its temperature would exceed 6000 degrees Celsius, being very close to that of the solar surface temperature.

The outer core is a coating that surrounds the inner core and that covers approximately the next 2,250 kilometers of material, which in this case is in a liquid state.

By inferences -result of scientific experimentation-, it is assumed that it presents temperatures around 5000 degrees centigrade on average.

Both components of the nucleus make up a circumference that is calculated to be between 3,200 and 3,500 kilometers in radius; this is quite close, for example, to the size of Mars (3,389.5 kilometers).

The nucleus represents 60% of the entire earth mass, and although its main elements are iron and nickel, the presence of a certain percentage of oxygen and sulfur is not ruled out.

Mantle

After the earth's core we find the mantle that extends approximately 2900 kilometers below the earth's crust, covering the core in turn.

Unlike the core, the chemical composition of the mantle favors magnesium over nickel, and it preserves high iron concentrations as well. Slightly more than 45% of its molecular structure is made up of ferrous and magnesium oxides.

As in the case of the nucleus, a differentiation is also made based on the degree of stiffness observed in this layer at its level closest to the crust. This is how it is distinguished between the lower mantle and the upper mantle.

The main characteristic that produces their separation is the viscosity of both bands. The upper one - adjacent to the crust - is somewhat more rigid than the lower one, which explains the slow movement of the tectonic plates.

Even so, the relative plasticity of this layer (which reaches about 630 kilometers) favors the rearrangement of the great masses of the earth's crust.

The lower mantle projects up to 2,880 kilometers deep to meet the outer core. Studies show that it is a basically solid zone with very low levels of flexibility.

Temperature

In general, the temperature in the earth's mantle ranges between 1000 and 3000 degrees Celsius as it approaches the core, which transmits much of its heat.

Under certain conditions, exchanges of fluids and materials are generated between the mantle and the crust, which are manifested in natural phenomena such as volcanic eruptions, geysers and earthquakes, among others.

Characteristics of the earth's crust

-The depth of the earth's crust ranges from 5 kilometers to 70 kilometers at its highest point.

-There are two types of earth's crust: oceanic and continental. The first represents the seabed and is normally thinner than the continental one. There are considerable differences between the two types of bark.

-The composition of the earth's crust includes sedimentary, igneous and metamorphic rocks.

-It is located on top of the Earth's mantle.

-The boundary between the mantle and the earth's crust is demarcated by the so-called Mohorovičić discontinuity, which is located under an average depth of 35 kilometers and fulfills the functions of a transition element.

-The deeper it is, the higher the temperature of the earth's crust. The average range covered by this layer is from 500 ° C to 1000 ° C at the point closest to the mantle.

-The Earth's crust together with a rigid fraction of the mantle make up the lithosphere, the outermost layer of the Earth.

-The largest component of the earth's crust is silica, represented in various minerals that contain it and that are found there.

Types

Ocean crust

This crust is thinner than its counterpart (it covers 5 to 10 kilometers) and covers approximately 55% of the Earth's surface.

It is made up of three well differentiated levels. The first level is the most superficial and in this there are various sediments that settle on the magmatic crust.

A second level below the first has a set of volcanic rocks called basalts, which have characteristics similar to gabros, igneous rocks with basic characteristics.

Finally, the third level of the oceanic crust is the one that is in contact with the mantle through the Mohorovičić discontinuity, and is composed of rocks similar to those found in the second level: the gabbros.

The greatest extension of the oceanic crust is in the deep sea, although there are some manifestations that have been observed on the surface thanks to the action of the plates over time.

A unique characteristic of the oceanic crust is that a portion of its rocks is in constant recycling as a consequence of the subduction to which the lithosphere is subjected, the upper layer of which is comprised of the oceanic crust.

This implies that the oldest of these rocks is around 180 million years old, a small figure considering the age of planet Earth.

Continental crust

The origins of the rocks that make up the continental crust are more diverse; therefore, this layer of the Earth is characterized by being much more heterogeneous than the previous one.

The thickness of this crust ranges from 30 to 50 kilometers and the constituent rocks are less dense. In this layer it is usual to find rocks such as granite, which is absent in the oceanic crust.

Likewise, silica continues to form part of the composition of the continental crust; in fact, the most abundant minerals in this layer are silicate and aluminum. The oldest parts of this crust are approximately 4 billion years old.

The continental crust is created by tectonic plates; This explains the fact that the thickest areas of this crust occur in the higher mountain ranges.

The subduction process that it undergoes does not result in its destruction or recycling, so the continental crust will always maintain its age in relation to the oceanic crust. Several studies have even confirmed that part of the continental crust is the same age as planet Earth.

Structure

The crust of the globe has three different layers: sedimentary layer, granite layer and basalt layer.

-The sedimentary layer is formed by the rocky sediments resting on the continental spaces. It manifests itself in the folded rocks in the form of mountain ranges.

-The granite layer forms the base or foundation of the non-submerged continental areas. Like the previous one, it is a discontinuous layer that floats in gravitational balance on the basaltic layer.

-Finally, the basalt is a continuous layer that completely envelops the Earth and that marks the final separation between the crust and the earth's mantle.

Tectonic plates

The Earth is a living organism and it shows us every day. When it unleashes its forces, human beings are often in a state of vulnerability, although this does not prevent scientists around the world from studying its processes and developing schemes that seek their understanding.

Precisely one of these processes is the existence of tectonic plates and their behaviors. There are 15 large plates spread throughout the globe, namely:

-Antarctic plate.

-African plate.

-Caribbean plate.

-Arabic plate.

-Plate of coconuts.

-Australian plate.

-Eurasian plate.

-Indian plate.

-South American plate.

- Philippine plate.

-Nazca plate.

-Juan de Fuca plate.

-Pacific plate.

-North American plate.

-Scotia plate.

Additionally, there are more than 40 smaller plates that complement smaller spaces not occupied by the larger plates. This forms a whole dynamic system that interacts perennially and affects the stability of the planet's crust.

Chemical composition

Noemiesquinas

The earth's crust houses life on the planet with all its variety. The elements that compose it are as heterogeneous as life itself, with all its manifestations.

Contrary to the subsequent layers - which, as we have seen, are basically made up of iron-nickel and iron-magnesium depending on the case - the earth's crust displays a wide range that serves nature to show its full potential.

Making a concise inventory we have that the earth's crust has the following chemical composition in percentage terms:

-Oxygen: 46%.

-Silicon 28%.

-Aluminum 8%.

-Iron 6%.

-Calcium 3.6%.

-Sodium 2.8%.

-Potassium 2.6%.

-Magnesium 1.5%.

These eight elements comprise an approximate percentage of 98.5% and it is not at all strange to see oxygen top the list. Not for nothing, water is an essential requirement for life.

The ability inherited by plants from primitive bacteria capable of producing oxygen through photosynthesis, has until now been a guarantee for its production at desired levels. The care of the great jungle and forested areas of the planet is undoubtedly an invaluable task in the purpose of maintaining an atmosphere suitable for life.

Movements

The first step in its mutation occurred about two hundred million years ago, in the period that we know as the Jurassic. Then Pangea was fractured in two great opposing groups: to the north Laurasia and to the south Gondwana. These two immense fragments moved west and east, respectively.

In turn, each one of these fractured, giving rise to North America and Eurasia, due to the rupture of Laurasia; and South America, Africa and Australia by the division of the Gondwana subcontinent.

Since then, some segments have been moving away or closer to each other, as in the case of the Indo-Australian plate, which after getting rid of its southern part merged into the Eurasian, originating the peaks of the Himalayas.

Such are the forces that govern these phenomena that even today it is known that Mount Everest - the highest point on Earth - grows at a rate of 4 millimeters each year as a result of the tremendous pressure still produced by the opposing tectonic plates.

Likewise, geological studies have revealed that America is moving away from the eastern hemisphere at a rate of approximately one inch per year; that is to say, at the beginning of the 20th century it was slightly more than three meters closer than it is today.

Training

Four thousand five hundred million years ago the face of the Earth was bubbling in the middle of an unimaginable chaos where meteors, comets, asteroids and other cosmic material were still raining, attracted by the gravity that the then protoplanet produced.

The duration of the days was barely six hours due to the dizzying speed with which the planet project rotated on its axis, the product of endless collisions with other smaller celestial stars and still affected by the effects of the original expansion.

Collision

Various studies have yielded a theory of the creation of the earth's crust that until recently was the most accepted. The estimate was that a small planetoid the size of Mars collided with Earth, which was still in its formation process.

As a result of this episode, the planet melted and became an ocean composed of magma. As a result of the impact, debris was generated that created the moon, and from this the Earth gradually cooled until it solidified. This is estimated to have occurred about 4.5 billion years ago.

New theory

In 2017 Don Baker - a scientist specializing in Earth from McGill University, in Canada - and Kassandra Sofonio - a specialist in Earth and planetary science, also from McGill University - established a new theory that is based on the already known, but adding an innovative element.

According to Baker, after the aforementioned collision, the Earth's atmosphere was filled with a very hot current that dissolved the most superficial rock on the planet. Dissolved minerals at this level rose to the atmosphere and cooled there.

Later, these minerals (mostly silicate) gradually separated from the atmosphere and fell back to the Earth's surface. Baker indicated that this phenomenon is called silicate rain.

Both researchers tested this theory by simulating these conditions within a laboratory. After the tests carried out, several scientists were surprised since the material obtained was practically the same as the silicate found in the earth's crust.

References

1. "Plate Tectonics" in Wikipedia. Retrieved on April 1, 2019 from Wikipedia: es.wikipedia.org
2. Morelle, R. "What is in the center of the Earth?" on BBC Mundo. Recovered in 1 anril 2019 from BBC Mundo: bbc.com
3. “The Himalayas» grows »four millimeters a year” in Informador. Retrieved on April 1, 2019 from Informador: informador.mx
4. Alden, A. "Why the Earth's Crust Is So Important?" at Thought Co. Retrieved on April 1, 2019 from Thought Co: thoughtco.com
5. Nace, T. "Layers Of The Earth: What Lies Beneath Earth's Crust" in Forbes. Retrieved on April 1, 2019 from Forbes: Forbes.com
6. "Crust" in National Geographic. Retrieved on April 1, 2019 in National Geographic: nationalgeographic.org
7. "Earth: Making of a Planet" on YouTube. Retrieved on April 1, 2019 from YouTube: com
8. Water, K. "New Theory on Earth's Crust Formation" in R&D. Retrieved on April 1, 2019 from R&D: rdmag.com
9. Condie, K. "Origin of the Earth's crust" in ScienceDirect. Retrieved on April 1, 2019 from ScienceDirect: sciencedirect.com