The earth is the object of study of a significant number of geosciences. The study of the Earth as a celestial body belongs to the field, the structure and composition of the Earth is studied by geology, the state of the atmosphere - meteorology, the totality of manifestations of life on the planet - biology. Geography gives a description of the features of the relief of the surface of the planet - oceans, seas, lakes and year, continents and islands, mountains and valleys, as well as settlements and societies. education: cities and villages, states, economic regions, etc.
Planetary characteristics
The Earth revolves around the star Sun in an elliptical orbit (very close to circular) at an average speed of 29,765 m/s at an average distance of 149,600,000 km per period, which is approximately equal to 365.24 days. The Earth has a satellite - which revolves around the Sun at an average distance of 384,400 km. Incline earth's axis to the plane of the ecliptic is 66 0 33 "22". The period of revolution of the planet around its axis is 23 hours 56 minutes 4.1 s. Rotation around its axis causes a change of day and night, and the tilt of the axis and circulation around the Sun - a change of seasons.
The shape of the Earth is geoid. The average radius of the Earth is 6371.032 km, equatorial - 6378.16 km, polar - 6356.777 km. Surface area the globe 510 million km ², volume - 1.083 10 12 km ², average density - 5518 kg / m ³. The mass of the Earth is 5976.10 21 kg. The earth has a magnetic field and a closely related electric field. The gravitational field of the Earth determines its close to spherical shape and the existence of the atmosphere.
According to modern cosmogonic concepts, the Earth was formed approximately 4.7 billion years ago from the gaseous matter scattered in the protosolar system. As a result of the differentiation of the Earth's matter, under the influence of its gravitational field, under the conditions of heating of the earth's interior, various shells - the geosphere - in chemical composition, state of aggregation and physical properties arose and developed: the core (in the center), the mantle, the earth's crust, the hydrosphere, the atmosphere, the magnetosphere . The composition of the Earth is dominated by iron (34.6%), oxygen (29.5%), silicon (15.2%), magnesium (12.7%). The Earth's crust, mantle and the inner part of the core are solid (the outer part of the core is considered liquid). From the surface of the Earth to the center, pressure, density and temperature increase. The pressure in the center of the planet is 3.6 10 11 Pa, the density is approximately 12.5 10 ³ kg / m ³, the temperature is in the range from 5000 to 6000 ° C. Main types earth's crust- continental and oceanic, in the transition zone from the mainland to the ocean, a crust of an intermediate structure is developed.
earth shape
The figure of the Earth is an idealization with which they try to describe the shape of the planet. Depending on the purpose of the description, various models of the shape of the Earth are used.
First approach
The most rough form of describing the figure of the Earth at the first approximation is a sphere. For most problems of general geography, this approximation seems to be sufficient to be used in the description or study of certain geographical processes. In such a case, the oblateness of the planet at the poles is rejected as an insignificant remark. The Earth has one axis of rotation and an equatorial plane - a plane of symmetry and a plane of symmetry of the meridians, which distinguishes it from the infinity of symmetry sets of an ideal sphere. The horizontal structure of the geographic shell is characterized by a certain zonation and a certain symmetry relative to the equator.
Second approximation
At a closer approximation, the figure of the Earth is equated to an ellipsoid of revolution. This model, characterized by a pronounced axis, the equatorial plane of symmetry and meridional planes, is used in geodesy for calculating coordinates, building cartographic networks, calculations, etc. The difference between the semiaxes of such an ellipsoid is 21 km, the major axis is 6378.160 km, the minor axis is 6356.777 km, the eccentricity is 1/298.25. The position of the surface can be easily calculated theoretically, but it cannot be determined experimentally in nature.
third approximation
Since the equatorial section of the Earth is also an ellipse with a difference in the lengths of the semiaxes of 200 m and an eccentricity of 1/30000, the third model is a triaxial ellipsoid. AT geographical research this model is almost never used, it only indicates the complex internal structure of the planet.
fourth approximation
The geoid is an equipotential surface coinciding with the average level of the World Ocean, it is a locus of points in space that have the same gravity potential. Such a surface has an irregular complex shape, i.e. is not a plane. The level surface at each point is perpendicular to the plumb line. The practical significance and importance of this model lies in the fact that only with the help of a plumb line, level, level and other geodetic instruments can one trace the position of level surfaces, i.e. in our case, the geoid.
Ocean and land
The general feature of the structure of the earth's surface is the distribution of the continents and oceans. Most of the Earth is occupied by the World Ocean (361.1 million km² 70.8%), the land is 149.1 million km² (29.2%), and forms six continents (Eurasia, Africa, North America, South America, and Australia) and islands. It rises above the world ocean level by an average of 875 m (the highest height is 8848 m - Mount Chomolungma), mountains occupy more than 1/3 of the land surface. Deserts cover about 20% of the land surface, forests - about 30%, glaciers - over 10%. The altitude amplitude on the planet reaches 20 km. The average depth of the world ocean is approximately equal to 3800 m (the greatest depth is 11020 m - the Mariana Trench (trough) in pacific ocean). The volume of water on the planet is 1370 million km³, the average salinity is 35 ‰ (g / l).
Geological structure
Geological structure of the Earth
The inner core, presumably, has a diameter of 2600 km and consists of pure iron or nickel, the outer core is 2250 km thick of molten iron or nickel, the mantle is about 2900 km thick and consists mainly of solid rocks, separated from the earth's crust by the Mohorovich surface. The crust and upper layer of the mantle form 12 main mobile blocks, some of which carry continents. Plateaus are constantly moving slowly, this movement is called tectonic drift.
The internal structure and composition of the "solid" Earth. 3. consists of three main geospheres: the earth's crust, mantle and core, which, in turn, is divided into a number of layers. The substance of these geospheres is different in physical properties, state and mineralogical composition. Depending on the magnitude of the velocities of seismic waves and the nature of their change with depth, the “solid” Earth is divided into eight seismic layers: A, B, C, D ", D", E, F and G. In addition, a particularly strong layer is isolated in the Earth the lithosphere and the next, softened layer - the asthenosphere Shar A, or the earth's crust, has a variable thickness (in the continental region - 33 km, in the oceanic - 6 km, on average - 18 km).
Under the mountains, the crust thickens; in the rift valleys of the mid-ocean ridges, it almost disappears. At the lower boundary of the earth's crust, the surface of Mohorovichich, seismic wave velocities increase abruptly, which is associated mainly with a change in the material composition with depth, the transition from granites and basalts to ultrabasic rocks of the upper mantle. Layers B, C, D ", D" are included in the mantle. Layers E, F and G form the core of the Earth with a radius of 3486 km At the border with the core (Gutenberg surface), the speed of longitudinal waves decreases sharply by 30%, and transverse waves disappear, which means that the outer core (layer E, stretches to a depth of 4980 km) liquid Below the transition layer F (4980-5120 km) there is a solid inner core (layer G), in which transverse waves again propagate.
The following chemical elements predominate in the solid earth's crust: oxygen (47.0%), silicon (29.0%), aluminum (8.05%), iron (4.65%), calcium (2.96%), sodium (2.5%), magnesium (1.87%), potassium (2.5%), titanium (0.45%), which add up to 98.98%. The rarest elements: Rho (approximately 2.10 -14%), Ra (2.10 -10%), Re (7.10 -8%), Au (4.3 10 -7%), Bi (9 10 -7%) etc.
As a result of magmatic, metamorphic, tectonic processes and processes of sedimentation, the earth's crust is sharply differentiated, complex processes of concentration and dispersion occur in it. chemical elements leading to the formation of various types of rocks.
It is believed that the upper mantle is close in composition to ultrabasic rocks, in which O (42.5%), Mg (25.9%), Si (19.0%) and Fe (9.85%) predominate. In terms of minerals, olivine reigns here, less pyroxenes. The lower mantle is considered an analogue of stone meteorites (chondrites). The Earth's core is similar in composition to iron meteorites and contains approximately 80% Fe, 9% Ni, 0.6% Co. Based on the meteorite model, the average composition of the Earth was calculated, in which Fe (35%), A (30%), Si (15%), and Mg (13%) predominate.
Temperature is one of the most important characteristics of the earth's interior, which makes it possible to explain the state of matter in various layers and build a general picture of global processes. According to measurements in wells, the temperature in the first kilometers increases with depth with a gradient of 20 ° C / km. At a depth of 100 km, where the primary foci of volcanoes are located, the average temperature is slightly lower than the melting temperature of rocks and is equal to 1100 ° C. At the same time, under the oceans at a depth of 100-200 km, the temperature is higher than in the continents by 100-200 ° C. The jump the density of matter in layer C per glybin at 420 km corresponds to a pressure of 1.4 10 10 Pa and is identified with a phase transition to olivine, which occurs at a temperature of approximately 1600 ° C. At the boundary with the core at a pressure of 1.4 10 11 Pa and temperature around 4000 °C, silicates are in a solid state, while iron is in a liquid state. In the transition layer F, where iron solidifies, the temperature can be 5000 ° C, in the center of the earth - 5000-6000 ° C, i.e., adequate to the temperature of the Sun.
Earth's atmosphere
The atmosphere of the Earth, the total mass of which is 5.15 10 15 tons, consists of air - a mixture of mainly nitrogen (78.08%) and oxygen (20.95%), 0.93% argon, 0.03% carbon dioxide, the rest is water vapor, as well as inert and other gases. The maximum land surface temperature is 57-58 °C (in the tropical deserts of Africa and North America), the minimum is about -90 ° C (in the central regions of Antarctica).
The Earth's atmosphere protects all life from the harmful effects of cosmic radiation.
The chemical composition of the Earth's atmosphere: 78.1% - nitrogen, 20 - oxygen, 0.9 - argon, the rest - carbon dioxide, water vapor, hydrogen, helium, neon.
Earth's atmosphere includes :
- troposphere (up to 15 km)
- stratosphere (15-100 km)
- ionosphere (100 - 500 km).
Weather and climate
The lower layer of the atmosphere is called the troposphere. There are phenomena that determine the weather. Due to the uneven heating of the Earth's surface by solar radiation, the circulation of large masses of air incessantly takes place in the troposphere. The main air currents in the Earth's atmosphere are the trade winds in the band up to 30° along the equator and the temperate westerly winds in the band from 30° to 60°. Another factor in heat transfer is the system of ocean currents.
Water has a constant circulation on the surface of the earth. Evaporating from the surface of water and land, under favorable conditions, water vapor rises in the atmosphere, which leads to the formation of clouds. Water returns to the surface of the earth in the form of precipitation and flows down to the seas and oceans through the year system.
The amount of solar energy that the Earth's surface receives decreases with increasing latitude. The farther from the equator, the smaller the angle of incidence of the sun's rays on the surface, and the greater the distance that the beam must travel in the atmosphere. As a consequence, the mean annual temperature at sea level decreases by about 0.4 °C per degree of latitude. The surface of the Earth is divided into latitudinal zones with approximately the same climate: tropical, subtropical, temperate and polar. The classification of climates depends on temperature and rainfall. The Köppen climate classification has received the greatest recognition, according to which five broad groups are distinguished - humid tropics, desert, humid mid-latitudes, continental climate, cold polar climate. Each of these groups is divided into specific pidrupa.
Human influence on the Earth's atmosphere
The Earth's atmosphere is significantly influenced by human activity. About 300 million cars annually emit 400 million tons of carbon oxides, more than 100 million tons of carbohydrates, hundreds of thousands of tons of lead into the atmosphere. Powerful producers of emissions into the atmosphere: thermal power plants, metallurgical, chemical, petrochemical, cellulose and other industries, motor vehicles.
The systematic inhalation of polluted air significantly worsens people's health. Gaseous and dust impurities can give the air an unpleasant odor, irritate the mucous membranes of the eyes, upper respiratory tract and thereby reduce their protective functions, cause chronic bronchitis and lung diseases. Numerous studies have shown that against the background of pathological abnormalities in the body (diseases of the lungs, heart, liver, kidneys and other organs), the harmful effects of atmospheric pollution are more pronounced. Important environmental problem there was acid rain. Every year, when fuel is burned, up to 15 million tons of sulfur dioxide enters the atmosphere, which, combined with water, forms a weak solution of sulfuric acid, which, together with rain, falls to the ground. acid rain negatively affect people, crops, buildings, etc.
Outdoor air pollution can also indirectly affect human health and sanitation.
The accumulation of carbon dioxide in the atmosphere can cause climate warming as a result of the greenhouse effect. Its essence lies in the fact that a layer of carbon dioxide, which freely passes solar radiation to the Earth, will delay the return of thermal radiation to the upper atmosphere. In this regard, the temperature in the lower layers of the atmosphere will rise, which, in turn, will lead to the melting of glaciers, snow, a rise in the level of the oceans and seas, and the flooding of a significant part of the land.
Story
Earth formed approximately 4540 million years ago with a disk-shaped protoplanetary cloud along with other planets solar system. The formation of the Earth as a result of accretion lasted 10-20 million years. At first, the Earth was completely molten, but gradually cooled down, and a thin hard shell formed on its surface - the earth's crust.
Shortly after the formation of the Earth, approximately 4530 million years ago, the Moon was formed. The modern theory of the formation of a single natural satellite of the Earth claims that this happened as a result of a collision with a massive celestial body, which was named Thea.
The Earth's primary atmosphere was formed as a result of the degassing of rocks and volcanic activity. Condensed water from the atmosphere, forming the World Ocean. Despite the fact that the Sun was 70% weaker then than it is now, geological evidence shows that the ocean did not freeze, possibly due to the greenhouse effect. Approximately 3.5 billion years ago, the Earth's magnetic field formed, which protected its atmosphere from the solar wind.
The formation of the Earth and the initial stage of its development (approximately 1.2 billion years long) belong to pregeological history. The absolute age of the oldest rocks is over 3.5 billion years and, starting from that moment, counts geological history Earth, which is divided into two unequal stages: the Precambrian, which occupies approximately 5/6 of the entire geological chronology (about 3 billion years), and the Phanerozoic, covering the last 570 million years. About 3-3.5 billion years ago, as a result of the natural evolution of matter on Earth, life arose, the development of the biosphere began - the totality of all living organisms (the so-called living matter of the Earth), which significantly influenced the development of the atmosphere, hydrosphere and geosphere (at least in parts of the sedimentary shell). As a result of the oxygen catastrophe, the activity of living organisms changed the composition of the Earth's atmosphere, enriching it with oxygen, which created an opportunity for the development of aerobic living beings.
A new factor that has a powerful influence on the biosphere and even the geosphere is the activity of mankind, which appeared on Earth after the appearance as a result of human evolution less than 3 million years ago (unity regarding dating has not been achieved and some researchers believe - 7 million years ago). Accordingly, in the process of development of the biosphere, formations and the further development of the noosphere, the shell of the Earth, which is greatly influenced by human activities, are distinguished.
The high growth rate of the world's population (the number of the earth's population was 275 million in 1000, 1.6 billion in 1900 and about 6.7 billion in 2009) and the increasing influence human society on the natural environment put forward the problems of rational use of all natural resources and nature protection.
Layers of the Earth pictures for kids. The main condition is that the child has an interest in the topics that this science deals with. You can try to awaken a child's desire to learn more about our planet by watching cartoons, movies or children's programs on this topic.
When studying complex voluminous topics, try to use visual didactic materials. A very good way is to make these manuals with your child.
In teaching a child at home, you can include a geography lesson on the structure of the Earth. To do this, you will need a sectional drawing of our planet, with the designation of all its layers: the earth's crust, mantle, outer and inner core.
After that, you can invite the child to color and name the different layers in the drawing of the Earth on their own, as well as estimate its size, for this, the approximate diameter of the globe in kilometers is given below.
For greater clarity, prepare several drawings, where all layers are black and white, and one is color. Attach plates with the name of the color layer and a brief description of it to such drawings.
Also prepare in advance four circles of different diameters from colored paper that matches the color of the layers of the Earth in your drawing. Invite the child to make his own model of the planet. Let him take circles from colored paper, correlate them with the tablets, determining which layer of the Earth each of them corresponds to.
If the child has already learned to read, have him read the appropriate sign aloud. brief description. If not, read it for yourself. Then you need to glue the circles correctly and sign all the layers. At the end, repeat all the new information again.
In a similar way, geography is taught for kids who still cannot understand and learn too complex topics. It will be interesting for younger children to make a model of our planet from a foam ball with their own hands, painting it with watercolors or gouache. A globe can be used as an example. First, explain that the Earth is actually round, and the globe is a small copy of it. In the process of work, explain to the baby that the blue color on the globe indicates the seas and oceans, brown - mountains, green - plains, and white - ice.
Depending on how inquisitive your child is, delve into topics that interest him. With a self-made model of the Earth, you can come up with various games for the development of kids: for example, demonstrate how the planet revolves around the Sun and its axis and how night follows day.
Layers of the earth for children in pictures
How often, in search of answers to our questions about how the world works, we look up at the sky, the sun, the stars, look far, far away hundreds of light years in search of new galaxies. But, if you look under your feet, then under your feet there is a whole underground world that our planet - Earth consists of!
Bowels of the earth this is the same mysterious world under our feet, the underground organism of our Earth, on which we live, build houses, lay roads, bridges, and for many thousands of years we have been developing the territories of our native planet.
This world is the secret depths of the bowels of the Earth!
Earth structure
Our planet belongs to the terrestrial planets, and, like other planets, it consists of layers. The surface of the Earth consists of a solid shell of the earth's crust, an extremely viscous mantle is located deeper, and a metal core is located in the center, which consists of two parts, the outer one is liquid, the inner one is solid.
Interestingly, many objects of the Universe are so well studied that every schoolchild knows about them, spacecraft are sent into space for distant hundreds of thousands of kilometers, but it still remains an impossible task to climb into the deepest depths of our planet, so what is under the surface of the Earth is still remains a big mystery.
What can be inside our home planet with you? Simply put, what is the Earth made of, what is its internal structure? These questions have long troubled scientists. But it turned out that to clarify this issue is not so simple. Even with the help of ultra-modern technologies, a person can go deep inside only for a distance equal to fifteen kilometers, and this, of course, is not enough to understand and justify everything. Therefore, even today, research on the topic “what the Earth consists of” is carried out mainly using indirect data and assumptions-hypotheses. But in this, scientists have already achieved certain results.
How the planet is studied
Even in the times of the ancients, individual representatives of mankind sought to know: what the Earth consists of. People also studied rock cuts exposed by nature itself and available for viewing. These are, first of all, cliffs, mountain slopes, steep coast of seas and rivers. From these natural cuts, a lot of things can be understood, because they consist of those rocks that were here and millions of years ago. And today, scientists are drilling wells in some places on land. Of these, the deepest - 15 km. Rock samples are also extracted from them that can tell people about what the Earth is made of.
Indirect data
But this is what concerns experiential and visual knowledge about the structure of the planet. But with the help of the science of seismology (the study of earthquakes) and geophysics, scientists penetrate into the depths without contact, analyzing seismic waves and their propagation. These data tell us about the properties of substances that are deep underground. The structure of the planet is also being studied with the help of artificial satellites that are in orbit.
What is the planet Earth made of?
The internal structure of the planet is heterogeneous. Today, research scientists have found that the inside consists of several parts. In the middle is the core. Next is the mantle, which is huge and makes up about five-sixths of the entire outer crust is represented by a thin layer covering the sphere. These three components, in turn, are also not entirely homogeneous and have structural features.
Core
What is the core of the earth made of? Scientists put forward several versions of the composition and origin of the central part of the planet. The most popular: the core is an iron-nickel melt. The core is divided into several parts: internal - solid, external - liquid. It is very heavy: it makes up more than a third of the total mass of the planet (for comparison, its volume is only 15%). According to scientists, it was formed gradually, over time, and iron and nickel were released from silicates. Currently (in 2015), scientists from Oxford have proposed a version according to which the nucleus consists of radioactive uranium. By this, by the way, they explain both the increased heat transfer of the planet, and the existence of a magnetic field to this day. In any case, information about what the core of the Earth consists of can only be obtained hypothetically, since prototypes are not available to modern science.
Mantle
What it consists of It should immediately be noted that, as in the case of the nucleus, scientists have not yet had a chance to get to it. Therefore, the study is also carried out with the help of theories and hypotheses. AT last years However, Japanese researchers are drilling at the bottom of the ocean, where “only” 3000 km will remain to the mantle. But the results have not yet been announced. And make up the mantle, according to scientists, silicates - rocks saturated with iron and magnesium. They are in a molten liquid state (the temperature reaches 2500 degrees). And, oddly enough, water is also part of the mantle. There is a lot of it there (if you throw out all the internal water to the surface, then the level of the world ocean would rise by 800 meters).
Earth's crust
It occupies only a little more than a percent of the planet by volume and a little less by mass. But, despite its low weight, it is very important for humanity, because it is on it that all life on Earth lives.
Spheres of the Earth
It is known that the age of our planet is approximately 4.5 billion years (scientists have found this out using radiometric data). When studying the Earth, several shells inherent in it, called geospheres, were revealed. They differ in their chemical composition and physical properties. The hydrosphere includes all the water available on the planet in its various states (liquid, solid, gaseous). The lithosphere is a stone shell tightly encircling the Earth (from 50 to 200 km thick). The biosphere is all life on the planet, including bacteria, plants, and people. The atmosphere (from the ancient Greek “atmos”, which means steam) is airy without which life would not exist.
What is the Earth's atmosphere made of?
The inner part of this most important shell for life is adjacent to and is a gaseous substance. And the outer one borders on outer space near the Earth. It determines the weather on the planet, and its composition is also not uniform. What is the earth's atmosphere made of? Modern scientists can accurately determine its components. Nitrogen in percentage terms - more than 75%. Oxygen - 23%. Argon - just over 1 percent. Quite a bit: carbon dioxide, neon, helium, methane, hydrogen, xenon and some other substances. The water content in varies from 0.2% to 2.5% depending on the climatic zone. The content of carbon dioxide is also unstable. Some characteristics of the modern Earth's atmosphere are directly dependent on human industrial activity.
The gaseous envelope that surrounds our planet Earth, known as the atmosphere, consists of five main layers. These layers originate on the surface of the planet, from sea level (sometimes below) and rise to outer space in the following sequence:
- Troposphere;
- Stratosphere;
- Mesosphere;
- Thermosphere;
- Exosphere.
Diagram of the main layers of the Earth's atmosphere
In between each of these main five layers are transitional zones called "pauses" where changes in air temperature, composition and density occur. Together with pauses, the Earth's atmosphere includes a total of 9 layers.
Troposphere: where the weather happens
Of all the layers of the atmosphere, the troposphere is the one with which we are most familiar (whether you realize it or not), since we live at its bottom - the surface of the planet. It envelops the surface of the Earth and extends upwards for several kilometers. The word troposphere means "change of the ball". A very fitting name, as this layer is where our day to day weather happens.
Starting from the surface of the planet, the troposphere rises to a height of 6 to 20 km. The lower third of the layer closest to us contains 50% of all atmospheric gases. It is the only part of the entire composition of the atmosphere that breathes. Due to the fact that the air is heated from below earth's surface, which absorbs the thermal energy of the Sun, with increasing altitude, the temperature and pressure of the troposphere decrease.
At the top is a thin layer called the tropopause, which is just a buffer between the troposphere and stratosphere.
Stratosphere: home of ozone
The stratosphere is the next layer of the atmosphere. It extends from 6-20 km to 50 km above the earth's surface. This is the layer in which most commercial airliners fly and balloons travel.
Here, the air does not flow up and down, but moves parallel to the surface in very fast air currents. Temperatures increase as you ascend, thanks to an abundance of naturally occurring ozone (O3), a by-product of solar radiation, and oxygen, which has the ability to absorb the sun's harmful ultraviolet rays (any rise in temperature with altitude is known in meteorology as an "inversion") .
Because the stratosphere has warmer temperatures at the bottom and cooler temperatures at the top, convection (vertical movements of air masses) is rare in this part of the atmosphere. In fact, you can view a storm raging in the troposphere from the stratosphere, since the layer acts as a "cap" for convection, through which storm clouds do not penetrate.
The stratosphere is again followed by a buffer layer, this time called the stratopause.
Mesosphere: middle atmosphere
The mesosphere is located approximately 50-80 km from the Earth's surface. The upper mesosphere is the coldest natural place on Earth, where temperatures can drop below -143°C.
Thermosphere: upper atmosphere
The mesosphere and mesopause are followed by the thermosphere, located between 80 and 700 km above the surface of the planet, and containing less than 0.01% of the total air in the atmospheric shell. Temperatures here reach up to +2000° C, but due to the strong rarefaction of the air and the lack of gas molecules to transfer heat, these high temperatures are perceived as very cold.
Exosphere: the boundary of the atmosphere and space
At an altitude of about 700-10,000 km above the earth's surface is the exosphere - the outer edge of the atmosphere, bordering space. Here meteorological satellites revolve around the Earth.
How about the ionosphere?
The ionosphere is not a separate layer, and in fact this term is used to refer to the atmosphere at an altitude of 60 to 1000 km. It includes the uppermost parts of the mesosphere, the entire thermosphere and part of the exosphere. The ionosphere gets its name because in this part of the atmosphere, the Sun's radiation is ionized when it passes the Earth's magnetic fields at and . This phenomenon is observed from the earth as the northern lights.