Humanity has set its sights on space since the day it existed and has accelerated space studies especially in recent years. In other words, we are full of enthusiasm to closely examine planets that are millions of light years away from us. What about our World? We know trees, oceans, people, etc. Do not think of the Earth, we see only the outer shell of this planet.
Yes, our Earth has a crust. Because under this shell, there are three more layers that we know for now. Each movement of these layers, which are thousands of kilometers below the crust, affects both our planet and us. Even if it is not layered like an onion, the layers of our Earth are still very interesting. Let’s take a closer look at what are the layers that make up the Earth and what are their properties.
Layers of the Earth:
- Shell
- Mantle
- Inner core
- Outer core
The layer where everything we see is the shell
The layer we are standing on right now, struggling with our daily rush, is the outer shell of our Earth, and it is the thinnest layer of this planet. Its thickness varies between 5 and 70 kilometers in places, but the average is 40 kilometers. Don’t look at how deep the depth is. On a planetary basis, it is thinner than the skin of an apple.
Earth’s crust is divided into terrestrial and oceanic. oceanic crust; As the name suggests, it is under the oceans, it is harder, deeper and consists of dense rocks such as basalt. The continental crust is much thicker and consists of granite-type rocks and some solutions.
The crust is not in a rigid immobility, it is divided into tectonic plates. These tectonic plates are divided into three main groups as proximal, divergent and transformative. It is known that these tectonic plates are not motionless, but rather float on a substrate called the mantle.
Earth’s thickest layer: Mantle
Just below the crust lies the mantle layer, about 2,890 kilometers thick. The mantle is Earth’s thickest layer and makes up 84 percent of the planet’s volume. The mantle has also been subjected to a basic classification according to its seismological features.
The upper mantle extends 670 kilometers down from the crust and consists of a rock called peridotite. The lower mantle begins immediately after the upper mantle. The mantle is not fixed, it is movable. There is a continuous circulation here, thanks to the hot material rising towards the surface and the cold material descending to the deep. This rotation moves tectonic plates in the crust.
As a result of tectonic movements, earthquakes occur in the crust as well as in the mantle. However, since there are no plates in the mantle, these earthquakes are thought to be caused by the volume change of the minerals changing state. Such earthquakes can also occur as a result of the interaction of hot and cold material.
Hot and solid: Inner core
In fact, the inner core is deeper than the outer core, but it would not be right to describe the outside without understanding the inside. The radius of the inner core is about 1220 kilometers and it is in a solid state. The temperature of the inner core is about 5400 degrees, which is quite hot.
The inner core grows rather slowly. As the entire core cools, some of the outer core joins the inner core. The cooling rate of the core is estimated to be 100 degrees in 1 billion years. Although slow, this growth directly affects the magnetic field of our Earth. The inner core is symmetrical on the east-west line.
Hotter and viscous: outer core
The radius of the outer core is about 3400 kilometers and it is in a liquid state. It is not quite correct to call the outer core liquid, instead, we can say that it is viscous. Due to this state, it is easily deformed. Its temperature is about 6000 degrees. It is agitated due to the severe convection current it is exposed to and affects the Earth’s magnetic field.
How do we know all this?
As we explained in the introduction, we as humanity do not like to go deep, but to go up. But curiosity is not the only reason. Even when you descend one layer of the crust, the temperature reaches terrifying degrees. In other words, it is extremely difficult to develop a machine that can withstand this temperature, let alone a human being to go there and observe.
So, how do we know the layers of the Earth that we can describe in such detail? Thanks to the seismic waves. Scientists send seismic waves as deep as they can through the crust. These waves provide information about the areas they pass each time they return.
After the information obtained by seismic waves is processed in the hands of experts, it is simulated beautifully, and we come across with Earth information as clear as if we had cut an apple and looked at it. Systems like earthquake scanning also provide important information about the layers of our Earth. So even if we don’t see it, we know it very well.
For those who want to get to know the planet we live in a little better, we answered the question of what are the layers that make up the Earth, and we talked about the important details you need to know about these layers. Although the data we have for today is clear, who knows, maybe we will see a new research tomorrow and learn that all we know is wrong.
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