What is the thickness of the earth?

The Earth’s diameter is more than 12,700 kilometers, yet the Kola ultra-deep well, the deepest well ever drilled by mankind, reaches a mere depth of 12.2 kilometers, which is a thousand times smaller. The knowledge scientists possess about the depths of outer space surpasses that of the Earth’s depths. Nevertheless, this does not hinder their ability to construct theories regarding its composition. What are the various layers that make up the Earth?

Techniques for investigating the structure of the Earth

The Earth’s structure can be analyzed using various methods. One approach involves calculating the planet’s volume by determining its radius. Additionally, the mass of the Earth can be determined by considering factors such as gravity, its orbit, and interactions with other celestial bodies. By knowing the volume and mass, it becomes possible to estimate the density of the Earth, which is found to be approximately 5515 kg/cubic meter. However, it is important to note that the average density of matter on the planet’s surface is significantly lower, measuring around 3000 kg/cubic meter. This suggests that there may be a substantial increase in density at greater depths.

When examining the composition of the Earth, scientists also depend on scientific experiments that simulate the high-pressure and high-density conditions found in the planet’s core. For instance, the density of iron increases by 1.3 times when subjected to a pressure of one million atmospheres due to the denser arrangement of atoms in its crystal lattice.

Seismic wave analysis during earthquakes is another valuable source of information about the Earth’s structure. In 1909, geophysicist Mohorovicich discovered that shallow earthquakes produce multiple acoustic signals, suggesting the presence of a distinct boundary between the crust and mantle known as the Mohorovicich surface.

Valuable material samples are brought to the surface from the depths of the Earth during volcanic eruptions. Additionally, studying other planets within the Earth group (Mercury, Venus, Mars) aids in the comprehension of the processes occurring in our planet’s interior, as these planets and the Earth underwent similar formation processes.

The outermost layer of the Earth is referred to as the Earth’s crust, with a thickness that ranges from 5 to 35 km. However, it is much thinner beneath the oceans. Some estimates suggest that the crust can reach a thickness of up to 70 km. Below the crust lies the upper mantle, which extends to a depth of 60 km. The lower part of the mantle reaches a depth of 2890 km. Geophysicists have identified a separate layer known as the asthenosphere, which is located between 100 and 200 km beneath the Earth’s surface.

The core of the Earth is located beneath the mantle. It is divided into an outer liquid layer, which extends to a depth of 5150 km, and an inner solid layer.

Earth’s crust

According to scientific knowledge, Venus and Mars (excluding Mercury) possess a comparable upper layer of crust as Earth. Nevertheless, Earth has two distinct types of crust: continental and oceanic. The continental crust, significantly older, can date back billions of years. It comprises three layers, with the uppermost layer consisting of rocks, the middle layer composed of granites and gneisses, and the bottom layer consisting of granulites and similar rock formations.

The process of oceanic crust formation occurs at mid-ocean ridges, which are found at the centers of the world’s oceans. This crust then moves in various directions before eventually being subducted into the mantle. The age of the oceanic crust is relatively young, typically not exceeding 140-150 million years. Additionally, it is much thinner compared to other crusts, estimated to be around 5-10 kilometers thick. As a result, the Pacific Ocean became the site of the first attempt to drill through the Earth’s crust, known as Project Mohol, which took place from 1961 to 1966.

Interestingly, the Earth’s crust is primarily composed of a small number of elements. The most abundant elements include oxygen (49%), silicon (26%), aluminum (7.5%), iron (4.2%), calcium (3.25%), sodium (2.4%), potassium (2.35%), and magnesium (2.35%).

• hydrogen (1%).

About 1% of the Earth’s crust is made up of the remaining elements.

Mantle

The mantle is estimated to extend as deep as 30 km in certain areas, although it has not yet been reached. The Mohorovicich surface marks the boundary between the mantle and the crust. This boundary is characterized by a significant increase in the speed of seismic waves and a corresponding increase in the density of matter.

The mantle is further divided into the upper and lower mantle. The boundary between them, known as the Golitsyn layer, is located at depths of 410-670 km. This region is where structural reorganization of the mantle material is observed.

The mantle exists in a liquid state, although it should not be mistaken for water. Its viscosity is incredibly high, measuring a quadrillion times greater than that of sand. This layer, which extends to depths of 2900 km, encompasses roughly 80% of the total volume of the Earth. Additionally, the mantle differs from the Earth’s crust in terms of its chemical makeup. Notably, it contains a lower proportion of aluminum and a significantly higher level of magnesium. The primary elements found within the mantle include:

• Oxygen (44.8%);
• Silicon (21.5%);
• Magnesium (22.8%);
• Iron (5.8%);
• Calcium (2.3%);
• Aluminum (2.2%).

Earth’s Core

The discovery of Earth’s core was first confirmed in 1897 by Johann Wichert. The core is composed of two layers – a liquid outer layer and a solid inner layer. However, in 2015, geologist Xiaodong Song proposed the existence of a third layer within the outer core.

The temperature within the outer core ranges from 4400°C at a depth of 2900 km to 6100°C at a depth of 5150 km. This region also experiences the flow of eddy electric currents, which generate Earth’s magnetic field through a phenomenon known as the geodynamo.

The pressure in the inner core can reach up to 375 GPa, making it impossible for the matter to turn into a liquid, despite the extremely high temperature of 6400°. This part of the planet’s structure did not form all at once, but rather around 2 billion (some estimates suggest only 500 million) years ago, as a result of the gradual cooling of the Earth. As time passed, the inner core has grown in size.

The chemical composition of the core differs significantly from that of the mantle. Approximately 85% of its mass consists of iron, while silicon makes up 6% and nickel accounts for another 5%. These figures are approximate, as determining the exact composition is incredibly challenging. It is possible that the core also contains significant amounts of sulfur, oxygen, carbon, phosphorus, and hydrogen.

What processes contributed to the formation of the Earth’s intricate structure?

The prevailing belief is that the Earth came into existence through the gradual attraction of multiple protoplanets, brought together by the force of gravity. Initially, it was in a completely liquid state. During this time, it experienced typical liquid processes, with heavier elements sinking deeper and lighter ones rising to the surface. Thus, over a span of approximately 10 million years, the Earth’s iron core was formed. There is a theory that suggests there were initially more radioactive metals, but they decayed over time. After the active phase of planet formation came to an end, the Earth began to cool down gradually, resulting in the solidification of the top layer and the formation of the Earth’s crust.

Planet Earth is an intricate celestial body. Its characteristics impact both the aspects of life on the planet and the very feasibility of its existence. The Earth’s layers play a significant role in this.

What are the Earth’s layers

The Earth’s layers are the strata of material that compose the entire planet. From the core to the outer atmosphere, the entire space is divided into multiple layers. There isn’t a distinct separation between them and often their substances can intermix, but each layer possesses its own boundaries and physical properties.

Categories of Earth’s Shells

The primary components of the Earth’s shell are known as the main ones. These consist of the hydrosphere, lithosphere, atmosphere, and biosphere. On the other hand, there are additional or secondary shells that are either extremely thin or immaterial.

For instance:

• The Earth’s core generates a magnetic field known as the magnetosphere, which has a significant impact on various processes occurring on the planet. In fact, it is even larger in size compared to the atmosphere.
• The ionosphere refers to the uppermost and least dense layers found in the atmosphere.
• The pedosphere encompasses the topsoil that covers both the land and the sea floor.

Aside from these, scientists are actively studying and classifying other shells of the Earth.

All shells can be categorized into two main groups – external and internal.

The Earth’s external shells

The group of external shells encompasses everything that is visible or accessible. This includes the hydrosphere, atmosphere, biosphere, and more. The interconnectedness of these Earth shells facilitates constant interaction between substances and objects within them.

Earth’s internal layers

According to the Earth’s layer scheme, all layers beneath the Earth’s crust are classified as internal. Since humans have not yet been able to reach the Earth’s core, scientists categorize the inner layers based on seismic wave velocity.

The internal layers can be divided into two groups:

• The planet’s mantle is composed of different layers, including the upper mantle (30-400 km), middle mantle (400-1000 km), and inner mantle (1000-2900 km). These layers contain the lithospheric plates, which are responsible for causing earthquakes.
• Additionally, the core of the planet can be divided into the outer core and the inner core. The core is primarily made up of liquid metals.

Inventory of Earth’s shell formations

Let’s take a look at the different formations that make up the Earth’s shell and their unique characteristics.

Lithosphere

The lithosphere is the outermost and hardest layer of the planet. Its upper boundary is the Earth’s surface, while its lower boundary is where the solid rock and minerals transition into a liquid state of lava. Below the solid lithosphere lies the molten asthenosphere. The lower layers of rock are able to shift and move through the asthenosphere with relative ease. This movement can lead to earthquakes as a result of layering or ruptures within the lithosphere. The lithosphere plays a crucial role in connecting the various shells of the Earth together.

There are significant compositional differences in the lithosphere between land and ocean. Underneath continents, the crust can be up to 80 km thick and primarily consists of sedimentary rocks, basalt, and granite.

The ocean floor, on the other hand, was formed in a different way. During the creation of the lithosphere, the internal heat from the asthenosphere caused partial melting of the ocean floor. This resulted in the deeper penetration of fusible materials into the crust, leaving mainly igneous rocks like dunite and harzburgite on the surface. The thickness of the oceanic lithosphere does not exceed 10 km.

The lithosphere undergoes various ongoing processes.

These processes can be categorized into three main types:

• Tectonic. They are connected with the movement of tectonic plates
• Volcanic. The magma that forms the asthenosphere can seep through cracks in the lithosphere and erupt at the surface from volcanoes. While this process is often seen as destructive, it plays a significant role in shaping the landscape.
• A variety of small-scale processes that can occur as a result of the planet’s gravitational pull or human activities. These include rockslides, landslides, avalanches, mudslides, etc.

The activity of the Earth’s lithosphere varies in different regions due to the diversity of tectonic processes. This results in some areas being more prone to seismic activity and volcanic eruptions than others.

Hydrosphere

The hydrosphere is the water envelope of the Earth. It covers over three-quarters of the planet’s surface area. It encompasses oceans and seas, rivers and lakes, marshes and groundwater, as well as mist, precipitation, and glaciers. A subdivision of the hydrosphere known as the “cryosphere” specifically refers to all the ice present on the planet (including permafrost, glaciers, and even snow).

Only 3% of the Earth’s water is freshwater. The remaining 97% is comprised of the salty water found in oceans and seas. Humanity has now developed the ability to desalinate water, but in certain regions of the world, it is still scarce.

The hydrosphere and the lithosphere have different processes. Water is always moving. Tides, ocean currents, precipitation, and cloud formation are all part of the continuous cycle of the lithosphere, which is also called the water cycle. The Earth’s favorable climate conditions allow water to exist in all three states on its surface.

Atmosphere

The atmosphere is the Earth’s gaseous covering. Similar to the lithosphere, it is influenced by various life forms. It stretches from the Earth’s surface to the vastness of outer space. Around 700-1000 kilometers above the Earth, the air becomes so sparse that it gradually merges with the emptiness of space.

There exist multiple distinct layers within the atmosphere:

• The lowest layer of the atmosphere is called the troposphere. It does not exceed a height of 15 km at different parts of the Earth. The upper boundary of the troposphere is determined by the pressure difference, as there is a 7-kilometer layer of ozone beyond it that protects the planet from ultraviolet radiation.
• Above the ozone layer is another layer called the stratosphere. The stratosphere extends up to 100 km from the Earth’s surface. It is mainly composed of hydrogen, helium, and other rarefied gases.
• The ionosphere starts at the stratosphere and extends all the way into space. At this altitude, substances break down into individual atoms and free electrons, which is why the ionosphere got its name. The phenomenon of the northern lights occurs in this layer.

Biosphere and Natural Complexes of Earth

The biosphere encompasses all the organisms that inhabit our planet, including plants, animals, fungi, and even the most basic life forms. These organisms interact with each other as well as with other components of Earth’s ecosystems, resulting in the production of valuable resources such as minerals, including oil, natural gas, and oxygen.

Extending approximately 1 kilometer above the Earth’s surface and reaching an equal depth into the soil, the biosphere plays a crucial role in maintaining the delicate balance of our planet.

The objects within the biosphere can be classified into 7 main groups:

1. Living organisms and plants
2. Biogenic matter is generated through the life processes of living organisms
3. Bone matter is formed independently of organisms (such as plant humus or animal carcasses).
4. Biocosmatter is formed from bone matter through natural processes. This includes silt and soil.
5. Radioactive substances that are in the process of decay.
6. Individual atoms
7. Various substances of extraterrestrial origin (meteorites, space dust).

The biosphere is constantly changing, unlike any other envelope. Over the course of Earth’s history, numerous species of organisms have emerged, developed, and become extinct. While scientists are actively researching the biosphere, they acknowledge that the organisms they have currently identified represent just a small portion of the total number, and it may take several more centuries to uncover them all.

Interconnection and interaction among the various layers of the Earth

The Earth’s layers have a profound impact on one another, leading to numerous interconnected processes. To better understand the relationship between the biosphere and the other layers of the Earth, it can be helpful to examine them in a table:

The Universe is the term used to describe everything that exists in the world around us. It is made up of galaxies, which are large groups of stars, as well as interstellar dust, gas, and planets. There are countless galaxies in the Universe, each with its own unique characteristics. One of these galaxies is the Milky Way, which is home to our solar system. Within our solar system, Earth is one of the planets. At the center of our solar system is the Sun, which is the brightest star. Other celestial bodies, such as planets and moons, orbit around the Sun.

Solar System Composition

The structure of the solar system is highly intricate. It encompasses planets along with their moons, asteroids, centaurs, comets, and interstellar debris.

The solar system comprises the terrestrial planets. These four celestial bodies are in closest proximity to the Sun: Mercury, Venus, Earth, and Mars.

Earth, which is the third planet from the Sun, belongs to the terrestrial planet group and is home to various forms of life. Scientific research suggests that Earth originated approximately 4.5 billion years ago from a solar nebula.

The formation of land in the form of ancient continents was a result of intricate processes taking place on the planet. Over time, these continents underwent splits and faults, eventually giving rise to the present-day continents.

While there is no direct evidence of the processes that occurred in the distant past, advancements in studying the Earth and outer space have enabled scientists to propose scientifically sound hypotheses.

Distinctive Features of the Earth

The Earth exhibits the form of a sphere, which is a generalized statement. In reality, the planet possesses the shape of a geoid. Directly translated from Greek, “geoid” denotes “resembling the Earth”.

The Earth’s surface displays diversity. It consists of towering mountains, expansive plains, and deep depressions. A ball, as commonly understood, has a flat surface. When viewed from outer space, the planet appears spherical. Thus, during our exploration of our planet, we uphold the belief that it possesses a spherical shape.

The shape of our planet is not a perfect sphere. It is slightly flattened at the poles and stretched at the equator. The polar radius of Earth measures approximately 6357 kilometers, while the equatorial radius is slightly larger at 6379 km. The circumference of the Earth at the equator is approximately 40,000 km.

In terms of size, Earth is the fifth largest planet in our solar system. It is smaller than Jupiter, Saturn, Uranus, and Neptune, which are known as the “giant planets”.

The distance between Earth and the Sun is approximately 149.6 million kilometers. It takes Earth 365 days and 6 hours to complete one revolution around the Sun. To account for this extra time, we have leap years, which occur every four years and add an extra day to the month of February.

The Sun is circled by Planet Earth at a velocity of 30 kilometers per second. All objects on the surface of the planet travel through space at this identical velocity.

Planet Earth possesses a natural satellite known as the Moon. The Moon revolves around Planet Earth in an elliptical path. The orbital period of the Moon lasts slightly longer than 27 days. When discussing the Earth in a fifth grade geography lesson, it is crucial to incorporate details about its companion, the Moon.

The Earth’s internal structure is characterized by distinct layers.

Firstly, there is the Earth’s crust, which is a solid, silicate layer with a thickness ranging from 5 to 70 km.

Next, we have the mantle, which is situated between the Earth’s crust and the core. The mantle can be further divided into two parts: the upper mantle and the lower mantle. The upper mantle is characterized by a viscous state, while the lower mantle is more solid in nature.

Lastly, there is the core, which is composed primarily of iron and nickel. The core itself can be divided into two distinct regions: the inner core and the outer core. The inner core is solid, while the outer core is molten.

It is common knowledge that Earth is the solitary planet within our solar system that supports life. However, the possibility of life existing in other systems and galaxies cannot be ruled out.

What have we gathered?

Earth is one of the many planets within our solar system. Its formation dates back 4.5 billion years. It is accompanied by a natural satellite, the moon. The most luminous entity within our system is the Sun. In addition to Earth, there are other types of planets, including gas giants and solid terrestrial planets.

Over 4 billion years ago, the captivating blue planet we now call Earth took shape from interstellar cosmic dust resulting from the explosions of new and supernovae stars, all under the influence of gravitational forces. It proudly stands as the third planet from the Sun within our solar system and is the only one to have been confirmed as harboring life.

Glossary

Asthenosphere – a layer located at a depth of approximately 150-200 km, consisting of partially molten and viscous material.

Lava – magma that has cooled and solidified on the Earth’s surface, devoid of gas.

Magma – a molten and fiery mass found in the asthenosphere, containing a significant amount of gases.

Lithospheric plates – large sections of the Earth’s crust that freely move within the viscous mantle.

Fold areas – regions of the Earth’s crust located between lithospheric plates that are in relative motion; they correspond to mountain systems on land and undersea ridges in topography.

Definition of lithosphere

The lithosphere, derived from the Greek words λίθος for “rock” and σφαίρα for “ball”, refers to the solid outer shell of the Earth. It serves as a protective covering for the planet, shielding it from the extreme temperatures of up to 60,000 °C emanating from the glowing core. Situated between the atmosphere and hydrosphere above, and the asthenosphere below, the lithosphere is not uniformly thick. Its thickness can vary from tens to several hundred kilometers across different regions.

Pangaea

Despite its ancient age, the planet’s formation remains ongoing. Both the Earth’s thin outer crust, which is home to humans, plants, and animals, and its hot interior are constantly in motion. The shapes of continents, landscapes, and climate conditions are in a state of continual change.

When we look at modern space images of Earth, with its outline of six separate continents, it is difficult to imagine that approximately 250 million years ago, there existed a single supercontinent known as Pangaea.

Due to the active processes within the Earth’s interior, this supercontinent eventually broke apart into the modern continents. Over millions of years, thanks to the slow movement of tectonic plates, which range from 2.5 cm to 7 cm per year (depending on various sources), these continents gradually drifted apart, reaching their current maximum distances.

When scaling towering mountains or exploring the depths of the ocean, humanity may feel like conquerors of nature. However, no man-made skyscraper can compare to the sheer heights of real mountains, and no bathyscaphe has reached the depths of the Mariana Trench.

The Earth’s lithosphere is not a continuous surface but is composed of separate plates. These plates come together in some areas, forming mountain ranges, while in other areas, they diverge to create sea trenches.

Scientists have identified eight major plates and numerous smaller ones within the lithosphere. These plates are not fixed, but rather slowly move through the hot, liquid asthenosphere. This movement causes seismic activity at the junctions where the plates meet.

This textbook is designed for students in grades 5-6 and is part of a series of geography textbooks edited by O.A. Klimanova and A.I. Alekseev. The textbook has a well-developed methodological framework that promotes developmental and student-centered learning. Additionally, students can enhance their understanding of the material by using the accompanying electronic appendix. This textbook is particularly suitable for gymnasiums and classes that focus on humanities subjects.

• Australia’s tectonic plate
• The plate in Antarctica
• The African tectonic plate
• The Eurasian plate
• The Indian tectonic plate
• The Pacific plate
• The North American tectonic plate
• The South American plate

Composition of the lithosphere

If we examine the Earth from a vertical perspective at the poles, we can identify the following layers: crust, boundary layer, mantle, and core.

The lithosphere consists of: the crust, the transition layer, and the uppermost, viscous layer of the mantle.

The lithosphere we are currently discussing represents only 1% of the Earth’s radius, but it is this 1% that enables life to exist on our planet.

The Earth’s crust is the topmost layer of the lithosphere. The diversity of the Earth’s crust is evident when standing on the shore and observing the layers of different rocks on a modest river’s cliff. Minerals discovered through excavations (such as oil, gas, iron ore, and diamonds) provide scientists with insights into the processes that occurred on our planet millions of years ago.

The Earth’s lithosphere is composed of various layers, with the crust being the uppermost and thinnest layer. Its thickness can range from 30 km on the plains to 80 kilometers on mountainous regions. The Earth’s crust can be categorized into two types: oceanic and continental. This classification is unique to our planet, as other celestial bodies lack such differentiation, as observed by space probes and planetoids.

Within the continental crust, there are three distinct rock layers:

• Sedimentary: This layer consists of rocks formed through sedimentation and volcanic processes.
• Granitic: Composed of metamorphic rocks, particularly quartz and feldspar.
• Basaltic: Resulting from the solidification of igneous rocks.

The oceanic crust, on the other hand, comprises sedimentary and basaltic layers.

Below the Earth’s crust lies the Mohorovicich boundary layer, which mirrors its shape and separates it from the mantle. This boundary is created when electrical discharge lightning occurs in the upper part of the mantle, resulting in a thin layer of ash.

The immense pressure exerted between the mantle and the Earth’s crust causes the ash layer to compress and behave like a dense, solid substance when seismic waves pass through it. The Mohorovicich surface serves as a hydro, electrical, and thermal insulator.

The mantle can be divided into two layers:

The outer layer of the mantle is liquid and the inner layer is dense, primarily consisting of iron and nickel.

Hot magma forms in the upper layer of the mantle and seeks to escape through faults in the Earth’s crust where tectonic plates converge. In the depths, ordinary coal transforms into the diamond, the most durable and precious stone, under the influence of pressure and temperature.diamond.

One might wonder, how do scientists come to this conclusion? After all, the Earth’s crust is approximately 60-70 kilometers thick, and the deepest man-made drilling rigs have only reached depths of slightly over 12 kilometers.

Volcanoes are not only dangerous, but also awe-inspiring displays of the fiery activity happening within the Earth’s core. By breaking through the Earth’s crust, molten magma is forcefully expelled to the surface. As it cools in the atmosphere, it transforms into streams of flowing lava, carrying volcanic rocks and gases. These elements provide scientists with valuable information about the deep-seated processes occurring beneath the Earth’s surface.

Deep fault lines in the Earth’s crust are home to a multitude of active volcanoes. The Pacific Ring of Fire, encompassing volcanic regions in Kamchatka, Japan, the Philippine Islands, Indonesia, Mexico, the Aleutian Islands, South America, and Tierra del Fuego, serves as a source of knowledge for scientists and a mesmerizing sight for observers.

However, the planet’s “breathing” and its vibrant life can also be witnessed in less harmful instances.

Within the ancient urban remains of the quaint town of Pozzuoli, situated on the coast of the Gulf of Naples, lies the remnants of an ancient temple and the adjoining marketplace, constructed over two millennia ago during the reign of the Roman Empire. Even a casual observer can discern that the marble columns have been eroded by the sea’s relentless forces, leaving them worn down by nearly 6 meters in height.

According to historical records, it is known that during the 13th century, the town square gradually sank below the level of the sea. This process took place over a long period of time and was not the result of a sudden earthquake or other catastrophic event. For three centuries, the remains of the buildings were submerged, but then the land slowly started to rise again. By 1800, the ruins were once again above sea level, and curious tourists can witness the fascinating phenomenon of bradyseisms, where the Earth’s surface rises and falls due to underground movements caused by the close proximity of a layer of magma to the Earth’s crust.

This textbook has been specifically designed for 7th grade students as part of the series of textbooks edited by O. A. Klimanova and A. I. Alekseev. One of the main objectives of this textbook is to increase the amount of country-specific information available to students. It explores the interrelationship between nature and economy, as well as the material and spiritual culture of the population in each country and territory. While the focus is primarily on countries in Eurasia, which is considered the “native continent” of Russians, Russia itself is also examined alongside other Eurasian countries.

Methodological advice

By utilizing guiding inquiries and visual aids such as tables and diagrams, children are educated about the motion of lithospheric plates, indicating their boundaries on the map.

1. The children draw the composition of the continental and oceanic crust.
2. Next, they examine samples of minerals from various sources to identify the distinctions between representatives of different lithospheric layers.
3. The concluding phase involves assessment on the subject.
4. From Pangea to 6 continents.Movement of lithospheric plates.

TEST

1. What is the name of the solid shell of the Earth?
2. the name of the ancient Greek goddess of fertility
3. the name of a single continent that once existed on planet Earth +
4. name of a planet in the Crab Nebula
5. oil tanker fires in the Pacific Ocean
6. active active volcanoes located along deep fault lines in the Earth’s crust +
7. swarms of glowing plankton visible in the Pacific Ocean at night
8. between the Earth’s crust and the upper layer of magma +
9. between the basaltic and sedimentary layers of the Earth’s crust.
10. between the lower magma layer and the Earth’s core.

The Earth, which is the third planet from the Sun and the fifth largest in size, holds the title for being the largest in mass, diameter, and density among all the celestial objects in its group. It is also known by other names such as the Blue Planet, Mir, or Terra. Currently, it is the only planet that is recognized for harboring life by humans.

Based on scientific studies, the Earth originated approximately 4.54 billion years ago from a solar nebula, and during its formation, it acquired a single natural satellite – the Moon. Life emerged on this planet roughly 3.9 billion years ago. Since then, the biosphere has significantly altered the composition of the atmosphere and other non-living elements. Consequently, the presence of aerobic organisms and the creation of the ozone layer became possible. The magnetic field, in conjunction with this layer, serves to mitigate the detrimental effects of solar radiation on life. Over time, the radiation emitted by the Earth’s crust has substantially diminished due to the gradual decay of radionuclides. The planet’s crust is divided into various tectonic plates, which shift a few centimeters each year.

About 70.8% of the Earth’s surface is covered by the world’s oceans, while the remaining portion is made up of continents and islands. Continents are home to various bodies of water such as rivers, lakes, groundwater, and ice. When combined with the World Ocean, these bodies of water make up the hydrosphere of the planet. Life can thrive thanks to the presence of liquid water both on the surface and underground. The Earth’s poles are covered by ice caps, which include the Antarctic ice sheet and the Arctic sea ice.

The inner regions of the Earth are highly active and consist of a thick, viscous layer known as the mantle. This layer surrounds an outer liquid core composed of nickel and iron. These physical characteristics of the planet have been able to support life for approximately 3.5 billion years. Scientists estimate that these conditions will persist for another 2 billion years.

The Earth is subject to the gravitational forces of other celestial bodies. Our planet orbits around the Sun completing a full revolution every 365.26 days. The Earth’s axis is tilted at an angle of 23.44°, which leads to the occurrence of seasonal changes that happen every tropical year. The duration of a day on Earth is approximately 24 hours. Meanwhile, the Moon orbits around the Earth, a phenomenon that has been occurring since time immemorial. Thanks to the Moon, ocean tides occur on our planet. Furthermore, the Moon plays a role in stabilizing the Earth’s tilt, gradually slowing down its rotation. There are theories suggesting that asteroids (bolides) have impacted the Earth in the past, directly affecting the organisms that existed at the time.

The evolution of our planet

The solar nebula hypothesis is the prevailing theory regarding the origins of our planet. According to this hypothesis, the Earth and the rest of the solar system formed from a vast cloud of gas and dust. This cloud consisted primarily of helium and hydrogen, which were products of the Big Bang. The cloud began to contract approximately 4.5 billion years ago, triggered by a shock wave from a nearby supernova explosion. As the cloud contracted, angular momentum, inertia, and gravity caused it to flatten into a protoplanetary disk. Within this disk, debris began to collide and merge under the influence of gravity, giving rise to the first planetoids.

The process of planet formation, known as accretion, led to the development of larger objects such as planets, by combining dust, gas, debris, and planetoids. This process took approximately 10-20 billion years.

The Moon, the Earth’s only satellite, was formed later and its origins are still not fully understood. Various hypotheses have been proposed, including one that suggests the Moon formed through accretion from Earth’s material remaining after a collision with a Mars-sized object. The collision vaporized and melted the Earth’s outer layer, causing part of the mantle to be ejected into orbit and eventually forming the Moon. This process resulted in the Moon’s depletion of metals and its unique composition. The Moon’s own gravity influenced its spherical shape and overall formation.

As the proto-earth grew through accretion, it also experienced intense heating, causing minerals and metals to melt. Siderophile elements, which have similar geochemical properties to iron, began to sink towards the Earth’s center, leading to the differentiation of the inner layers into the mantle and metallic core. This process also marked the formation of the planet’s magnetic field. Volcanic activity and the release of gases resulted in the creation of the atmosphere. As water vapor condensed with the help of ice, the oceans began to form. During this period, the Earth’s atmosphere primarily consisted of lighter elements like helium and hydrogen, but had a much higher concentration of carbon dioxide compared to the present. The magnetic field emerged approximately 3.5 billion years ago, playing a crucial role in shielding the atmosphere from the damaging effects of solar wind.

The surface of the planet has undergone continuous changes over hundreds of millions of years. New continents have formed and disappeared, and at times, they have come together to create supercontinents. Approximately 750 million years ago, the first supercontinent, Rodinia, started to break apart. Eventually, its fragments merged to form a new supercontinent called Pannotia. After another 540 million years, Pangaea emerged, only to break apart 180 million years later.

The Origin of Life on Earth

There are numerous hypotheses and theories regarding this topic. One of the most widely accepted theories suggests that approximately 3.5 billion years ago, a single universal ancestor gave rise to all the organisms we see today.

Thanks to the evolution of photosynthesis, living organisms were able to harness the energy of the sun. This led to the accumulation of oxygen in the atmosphere and the formation of an ozone layer in the upper atmosphere. Eukaryotes, which are the result of a symbiotic relationship between larger and smaller cells, began to emerge. Around 2.1 billion years ago, multicellular organisms made their appearance.

In 1960, scientists proposed the theory of the Earth-snowball, which suggests that between 750 and 580 million years ago, the entire surface of our planet was covered in ice. This theory provides a plausible explanation for the Cambrian explosion, which marks the sudden appearance of a wide variety of life forms. To date, substantial evidence has supported this hypothesis.

The emergence of the first algae occurred approximately 1200 million years ago, followed by the appearance of the first higher plants around 450 million years ago. Invertebrates appeared during the Ediacaran period, while vertebrates emerged during the Cambrian explosion.

Approximately 40 million years ago, the onset of the most recent ice age took place. The peak of this ice age happened during the Pleistocene epoch, around 3 million years ago.

The Earth’s Composition

Our planet is classified as part of the earth group and possesses a solid exterior. It boasts the highest density, mass, gravity, magnetic field, and size among all known celestial bodies. Notably, Earth stands as the sole planet recognized to have ongoing movement of tectonic plates.

The Earth’s composition is categorized into different layers according to their physical and chemical characteristics. However, unlike other celestial bodies, it possesses a unique outer and inner core. The outer layer is comprised of a solid shell primarily composed of silicate materials. This layer is separated from the mantle by a boundary where seismic longitudinal waves experience an increase in velocity. The lithosphere is formed by the upper, viscous portion of the mantle and the solid crust. Positioned beneath the lithosphere is the asthenosphere.

At a depth of 660 km, significant alterations take place in the crystalline composition. This demarcates the boundary between the upper mantle and the lower mantle. Beyond the mantle lies a liquid stratum comprised of molten iron infused with traces of sulfur, nickel, and silicon. Known as the Earth’s core, it has been revealed through seismic observations that the core is comprised of two distinct regions – an outer liquid region and an inner solid region.

The Earth is an oblate spheroid in shape. It has an average diameter of 12,742 km and a circumference of 40,000 km. The equatorial bulge is a result of the planet’s rotation, causing the equatorial diameter to be 43 km larger than the polar diameter. Mount Everest marks the highest point on Earth, while the Mariana Trench is the deepest point.

Chemical makeup

The Earth has an approximate mass of 5.9736-1024 kg and contains an estimated number of atoms ranging from 1.3-1.4-1050. Its chemical composition consists of various elements, with iron making up about 32.1%, oxygen accounting for 30.1%, silicon contributing 15.1%, magnesium comprising 13.9%, sulfur making up 2.9%, nickel accounting for 1.8%, calcium contributing 1.5%, and aluminum comprising 1.4%. The remaining elements make up approximately 1.2% of the Earth’s composition.

Structure inside

The Earth, similar to other planets, possesses a layered structure inside. It consists primarily of a metal core and tough silicate shells. The internal heat of the planet is generated by a combination of remaining heat and the decay of radioactive isotopes.

The lithosphere, which is the solid outer shell of the Earth, is made up of the upper part of the mantle and the crust. It is divided into movable fold belts and stable platforms. These lithospheric plates move over the plastic asthenosphere, which can be described as a viscous superheated fluid. This asthenosphere exhibits a decrease in the velocity of seismic waves.

The crust, which is the uppermost solid layer of the Earth, is separated from the mantle by the Mohorovitch boundary. There are two types of crust – oceanic and continental. Oceanic crust is composed of basic rocks and a sedimentary cover, while continental crust is composed of granite, sedimentary rocks, and basaltic rocks. The entire Earth’s crust is divided into lithospheric plates of various sizes, and these plates move in relation to one another.

The thickness of the continental crust on Earth ranges from 35 to 45 km, and in mountainous regions, it can reach up to 70 km. As we go deeper, the proportion of iron and magnesium oxides in the composition increases, while the amount of silica decreases. The upper part of the continental crust is made up of discontinuous layers of volcanic and sedimentary rocks, often folded into folds. Shields do not have a sedimentary layer. Right below them, there is a boundary layer of granites and gneisses. Beyond that lies a layer of basalt, which consists of gabbro, basalts, and metamorphic rocks. These layers are separated by a conventional boundary known as Conrad’s surface. In the oceanic crust, the thickness ranges from 5 to 10 km. It is also divided into two layers – the upper and lower. The upper layer is composed of sedimentary deposits that are about a kilometer thick, while the lower layer consists of basalt, serpentinite, and interlayers of sediments.

The Earth’s mantle is a shell made of silicate material that sits between the Earth’s core and its crust. It constitutes 67% of the total mass of the planet and approximately 83% of its volume. The mantle spans a wide range of depths and contains phase transitions that impact the density of mineral structures. Additionally, the mantle is divided into an upper and lower section, with the upper part consisting of the substrate, the Gutenberg layer, and the Golitsyn layer.

The findings of the current study indicate that the Earth’s mantle bears resemblance to chondrites, which are stone meteorites. The primary constituents consist of oxygen, silicon, iron, magnesium, and other chemical elements. These elements, alongside silicon dioxide, combine to form silicates.

The Core (geosphere) constitutes the deepest and most central part of the Earth. It is believed to be composed of iron-nickel alloys and siderophilic elements. The Core is located approximately 2900 km beneath the Earth’s surface, with an estimated radius of 3485 km. The temperature at the core can reach up to 6000°C, accompanied by pressures up to 360 GPa. The approximate mass of the Core is 1.9354-1024 kg.

The geographical envelope refers to the uppermost layers of the Earth. The Earth boasts a unique array of landforms. About 70.8% is covered by bodies of water. The underwater terrain is characterized by towering underwater mountain ranges, underwater volcanoes, expansive oceanic plateaus, deep troughs, submarine canyons, and vast abyssal plains. The remaining 29.2% is composed of terrestrial landforms such as deserts, mountains, plateaus, plains, and more.

The Earth’s surface is constantly being shaped by tectonic processes and erosion. Precipitation, temperature fluctuations, weathering, and chemical influences all contribute to the formation of the planet’s relief. Additionally, glaciers, coral reefs, meteorite impacts, and coastal erosion play significant roles in shaping the Earth’s surface.

The hydrosphere encompasses all of Earth’s water resources. One distinguishing characteristic of our planet is the existence of liquid water. The majority of this water is located in the seas and oceans. The combined mass of the world’s oceans is approximately 1.35 × 10^18 tons. Water can be classified into two categories: saltwater and freshwater, with only 2.5% of the latter being drinkable. The largest portion of freshwater is stored in glaciers, accounting for 68.7%.

Environment

The environment refers to the gas layer encircling the planet, comprised mainly of oxygen and nitrogen. Trace amounts of carbon dioxide and water vapor are also found within it. Over time, the environment has undergone significant changes as a result of the impact of living organisms. With the advent of oxygen-producing photosynthesis, aerobic life forms emerged and flourished. Serving as a protective shield, the environment shields the Earth from cosmic radiation and plays a vital role in shaping weather patterns. Additionally, it regulates the movement of air masses, the water cycle, and the transport of heat. The environment is categorized into various layers, including the stratosphere, mesosphere, thermosphere, ionosphere, and exosphere.