What is the body of the earth called? Earth's magnetic field

Earth

Earth

planet of the solar system, third in order from the sun. Orbits around it in an elliptical, close to circular orbit (with an eccentricity of 0.017), with cf. speed approx. 30 km/s. Wed. The distance of the Earth from the Sun is 149.6 million km, the period of revolution is 365.24 sr. sunny days(tropical year). On Wed. At a distance of 384.4 thousand km from the Earth, the natural satellite Moon revolves around it. The Earth rotates around its axis (having an inclination to the ecliptic plane equal to 66°33 22) in 23 hours 56 minutes (sidereal day). With the Earth's rotation around the Sun and tilt earth's axis The change of seasons on Earth is associated with the rotation of the Earth around its axis - the change of day and night.

Earth structure: 1– continental crust; 2 – oceanic crust; 3 – sedimentary rocks; 4 – granite layer; 5 – basalt layer; 6 – mantle; 7 – outer part of the core; 8 – inner core

The Earth has the shape of a geoid (approximately a triaxial ellipsoidal spheroid), cf. whose radius is 6371.0 km, equatorial – 6378.2 km, polar – 6356.8 km; dl. the circumference of the equator is 40075.7 km. Earth's surface area - 510.2 million km² (including land - 149 km², or 29.2%, seas and oceans - 361.1 million km², or 70.8%), volume - 1083 10 12 km³, weight – 5976·10 21 kg, avg. density – 5518 kg/m³. The Earth has a gravitational field that determines its spherical shape and firmly holds atmosphere, as well as a magnetic field and a closely related electric field. The composition of the Earth is dominated by iron (34.6%), oxygen (29.5%), silicon (15.2%) and magnesium (12.7%). Structure earth's bowels shown in the figure.

General view of the Earth from space

The conditions on Earth are favorable for the existence of life. The region of active life forms a special shell of the Earth - biosphere, it carries out biological circulation of substances and energy flows. The earth also has geographical envelope, characterized by a complex composition and structure. Many sciences study the Earth (astronomy, geodesy, geology, geochemistry, geophysics, physical geography, geoscience, biology, etc.).

Geography. Modern illustrated encyclopedia. - M.: Rosman. Edited by prof. A. P. Gorkina. 2006 .

Earth

the planet we live on; the third from the Sun and the fifth largest planet in the Solar System. The Solar System is believed to have formed from swirling gas and dust clouds ca. 5 billion years ago. Earth is rich in natural resources, has a generally favorable climate, and may be the only planet that supports life. In the interior of the Earth, active geodynamic processes occur, manifested in the spreading of the ocean floor (growth of the oceanic crust and its subsequent spreading), continental drift, earthquakes, volcanic eruptions, etc.
The earth rotates around its axis. Although this movement is not noticeable on the surface, a point on the equator moves at a speed of approx. 1600 km/h. The Earth also revolves around the Sun in an orbit of approx. 958 million km with average speed 29.8 km/s, completing a full revolution in about a year (365.242 average solar days). See also solar system.
PHYSICAL CHARACTERISTICS
Form and composition. The Earth is a sphere consisting of three layers - solid (lithosphere), liquid (hydrosphere) and gaseous (atmosphere). The density of the rocks that make up the lithosphere increases towards the center. The so-called "solid Earth" includes a core made primarily of iron, a mantle composed of lighter metal minerals (such as magnesium), and a relatively thin hard bark. In places it is fragmented (in fault areas) or folded (in mountain belts).
Under the influence of the gravity of the Sun, Moon and other planets throughout the year, the shape of the Earth's orbit and configuration change slightly, and tides also arise. On the Earth itself, a slow continental drift occurs, the ratio of land and oceans gradually changes, and in the process of the constant evolution of life, a transformation occurs environment. Life on Earth is concentrated in the contact zone of the lithosphere, hydrosphere and atmosphere. This zone, together with all living organisms, or biota, is called the biosphere. Outside the biosphere, life can only exist if there is special systems life support, such as spacecraft.
Shape and size. The approximate outlines and dimensions of the Earth have been known for more than 2000 years. Back in the 3rd century. BC The Greek scientist Eratosthenes quite accurately calculated the radius of the Earth. It is currently known that its equatorial diameter is 12,754 km, and its polar diameter is approx. 12,711 km. Geometrically, the Earth is a triaxial ellipsoidal spheroid, flattened at the poles (Fig. 1, 2). Earth's surface area is approx. 510 million km 2, of which 361 million km 2 is water. The volume of the Earth is approx. 1121 billion km 3.
The inequality of the Earth's radii is partly due to the rotation of the planet, which results in a centrifugal force that is maximum at the equator and weakens towards the poles. If only this force were acting on the Earth, all objects on its surface would fly into space, but due to the force of gravity, this does not happen.
The force of earth's attraction, or gravity, keeps the moon in orbit and the atmosphere close to the earth's surface. Due to the rotation of the Earth and the action of centrifugal force, gravity on its surface decreases somewhat. The force of gravity causes acceleration free fall objects, the value of which is approximately 9.8 m/s 2.
The heterogeneity of the earth's surface determines differences in gravity in different areas. Measurements of gravity acceleration provide information about the internal structure of the Earth. For example, higher values ​​are observed near mountains. If the values ​​are lower than expected, then it can be assumed that the mountains are composed of less dense rocks. See also geodesy
Mass and density. The mass of the Earth is approx. 6000×10 18 tons. For comparison, the mass of Jupiter is approximately 318 times greater, the Sun - 333 thousand times. On the other hand, the Earth's mass is 81.8 times that of the Moon. The Earth's density varies from negligible in the upper atmosphere to extremely high in the center of the planet. Knowing the mass and volume of the Earth, scientists calculated that it average density approximately 5.5 times more density water. One of the most common rocks on the Earth's surface, granite has a density of 2.7 g/cm3, the density in the mantle varies from 3 to 5 g/cm3, within the core from 8 to 15 g/cm3. At the center of the Earth it can reach 17 g/cm3. In contrast, the density of air at the earth's surface is approximately 1/800 that of water, and in the upper atmosphere it is very low.
Pressure. The atmosphere exerts a pressure on the earth's surface at sea level with a force of 1 kg/cm2 (pressure of one atmosphere), which decreases with altitude. At an altitude of approx. After 8 km it drops by about two-thirds. Inside the Earth, the pressure increases rapidly: at the boundary of the core it is approx. 1.5 million atmospheres, and in its center - up to 3.7 million atmospheres.
Temperatures on Earth vary greatly. For example, a record high temperature of +58° C was recorded in Al-Azizia (Libya) on September 13, 1922, and a record low, -89.2° C, at Vostok station near the South Pole in Antarctica on July 21, 1983. With depth during the first kilometers from the earth's surface, the temperature rises by 0.6 ° C every 18 m, then this process slows down. The core located in the center of the Earth is heated to a temperature of 5000–6000 ° C. In the near-surface layer of the atmosphere, the average air temperature is 15 ° C, in the troposphere (the lower main part of the Earth’s atmosphere) it gradually decreases, and above (starting from the stratosphere) it varies widely depending on absolute altitude.
The shell of the Earth, within which temperatures are usually below 0 ° C, is called the cryosphere. In the tropics it begins at an altitude of approx. 4500 m, in high latitudes (north and south of 60–70°) - from sea level. In subpolar regions on continents, the cryosphere can extend several tens of hundreds of meters below the earth's surface, forming a permafrost horizon.
Geomagnetism. Back in 1600, the English physicist W. Gilbert showed that the Earth behaves like a huge magnet. Turbulent movements in the molten iron-bearing outer core appear to generate electric currents that create a strong magnetic field that extends more than 64,000 km into space. The force lines of this field leave one magnetic pole of the Earth and enter the other (Fig. 3). Magnetic poles move around geographic poles Earth. The geomagnetic field drifts in westward at a speed of 24 km/year. Currently Northern magnetic pole located among the islands of northern Canada. Scientists believe that over long periods of geological history, the magnetic poles roughly coincided with the geographic ones. At any point on the earth's surface, the magnetic field is characterized by a horizontal component of intensity, magnetic declination(the angle between this component and the plane of the geographic meridian) and magnetic inclination (the angle between the intensity vector and the horizon plane). At the North Magnetic Pole, the compass needle, which is mounted vertically, will point straight down, and at the South Magnetic Pole, it will point straight up. However, at the magnetic pole, the needle of a compass placed horizontally rotates randomly around its axis, so the compass is useless for navigation here. See also geomagnetism.
Geomagnetism determines the existence of an external magnetic field – the magnetosphere. Currently, the North magnetic pole corresponds to a positive sign ( power lines fields are directed inside the Earth), and the Southern one is negative (field lines are directed outward). In the geological past, the polarity has been reversed from time to time. Solar wind (stream elementary particles, emitted by the Sun) deforms the Earth’s magnetic field: on the day side facing the Sun it is compressed, and on the opposite, night side, it is stretched into the so-called. Earth's magnetic tail.
Below 1,000 km, electromagnetic particles in the thin upper layer of the Earth's atmosphere collide with oxygen and nitrogen molecules, exciting them, resulting in a glow known as the aurora, fully visible only from space. The most impressive auroras are associated with solar magnetic storms synchronous with the maxima solar activity, having a cyclicity of 11 years and 22 years. Currently the Northern Lights in the best possible way visible from Canada and Alaska. In the Middle Ages, when the magnetic north pole was located further east, the aurora was often visible in Scandinavia, northern Russia and northern China.
STRUCTURE
Lithosphere(from the Greek lithos - stone and sphaira - ball) - the shell of the “solid” Earth. Previously, it was believed that the Earth consists of a hard thin crust and a hot boiling melt underneath, and only the hard crust was classified as the lithosphere. Today it is believed that the “solid” Earth includes three concentric shells called the crust, mantle and core (Fig. 4). The earth's crust and upper mantle are solid bodies, the outer part of the core behaves like a liquid medium, and the inner part behaves like solid. Seismologists classify the earth's crust and upper mantle as the lithosphere. The base of the lithosphere is located at depths from 100 to 160 km at the contact with the asthenosphere (a zone of reduced hardness, strength and viscosity within the upper mantle, presumably consisting of molten rocks).
Earth's crust– the thin outer shell of the Earth with an average thickness of 32 km. It is thinnest under the oceans (from 4 to 10 km), and most powerful under the continents (from 13 to 90 km). The crust accounts for approximately 5% of the Earth's volume.
A distinction is made between continental and oceanic crust (Fig. 5). The first of them was previously called sial, since the granites and some other rocks that compose it contain mainly silicon (Si) and aluminum (Al). The oceanic crust was called sima because of the predominance of silicon (Si) and magnesium (Mg) in its rock composition. It usually consists of dark-colored basalts, often of volcanic origin. There are also areas with transitional crust, where oceanic crust slowly turns into continental crust or, conversely, part of the continental crust turns into oceanic crust. This kind of transformation occurs in the process of partial or complete melting, as well as as a result of crustal dynamic processes.
About a third of the earth's surface is land, consisting of six continents (Eurasia, North and South America, Australia and Antarctica), islands and groups of islands (archipelagos). Most of the land is located in the Northern Hemisphere. The relative positions of the continents have changed throughout geological history. About 200 million years ago, the continents were located mainly in the Southern Hemisphere and formed the giant supercontinent Gondwana (cm. Also GEOLOGY).
The height of the surface of the earth's crust varies significantly from area to area: the most high point on Earth - Mount Qomolungma (Everest) in the Himalayas (8848 m above sea level), and the lowest is at the bottom of the Challenger Deep in the Mariana Trench near the Philippines (11,033 m below sea level). Thus, the amplitude of the heights of the surface of the earth’s crust is more than 19 km. In general, mountainous countries with altitudes above 820 m above sea level. m occupy approximately 17% of the Earth's surface, and the rest of the land area - less than 12%. About 58% of the earth's surface is in deep-sea (3–5 km) ocean basins, and 13% is in fairly shallow continental shelves and transitional areas. The shelf edge is usually located at a depth of approx. 200 m.
It is extremely rare that direct research can cover layers of the earth’s crust located deeper than 1.5 km (as, for example, in the gold mines of South Africa with a depth of over 3 km, oil wells of Texas with a depth of about 8 km and in the deepest in the world - more than 12 km - Kola experimental drilling well). Based on the study of these and other wells, a large amount of information has been obtained about the composition, temperature and other properties of the earth's crust. In addition, in areas of intense tectonic movements, for example, in the Grand Canyon of the Colorado River and in mountainous countries, it was possible to gain a detailed understanding of deep structure earth's crust.
It has been established that earth's crust consists of solid rocks. The exception is volcanic zones, where there are pockets of molten rock, or magma, that flow to the surface in the form of lava. In general, the rocks of the earth's crust consist of approximately 75% oxygen and silicon and 13% aluminum and iron. Combinations of these and some other elements form the minerals that make up rocks. Sometimes important substances are found in the earth's crust in significant concentrations. economic importance individual chemical elements and minerals. These include carbon (diamonds and graphite), sulfur, ores of gold, silver, iron, copper, lead, zinc, aluminum and other metals. See also mineral resources; minerals and mineralogy.
Mantle- the shell of the “solid” Earth, located under the earth’s crust and extending to a depth of approximately 2900 km. It is divided into the upper (about 900 km thick) and lower (about 1900 km thick) mantle and consists of dense greenish-black iron-magnesium silicates (peridotite, dunite, eclogite). In conditions surface temperatures and pressure, these rocks are approximately twice as hard as granite, and at great depths they become plastic and flow slowly. Thanks to the breakup radioactive elements(especially potassium and uranium isotopes), the mantle gradually heats up from below. Sometimes, during the process of mountain building, blocks of the earth's crust are immersed in the mantle material, where they melt, and then during volcanic eruptions, along with lava, they are carried to the surface (sometimes the lava includes fragments of peridotite, dunite and eclogite).
In 1909, the Croatian geophysicist A. Mohorovicic established that the speed of propagation of longitudinal seismic waves increases sharply at a depth of approx. 35 km under the continents and 5–10 km under the ocean floor. This boundary corresponds to the boundary between the earth's crust and mantle and is called the Mohorovicic surface. The position of the lower boundary of the upper mantle is less certain. Longitudinal waves, penetrating into the mantle, propagate with acceleration until they reach the asthenosphere, where their movement slows down. The lower mantle, in which the speed of these waves increases again, is more rigid than the asthenosphere, but somewhat more elastic than the upper mantle.
Core The earth is divided into external and internal. The first of them begins at approximately 2900 km depth and has a thickness of approx. 2100 km. The boundary between the lower mantle and the outer core is known as the Gutenberg layer. Within its limits, longitudinal waves slow down, and transverse waves do not propagate at all. This indicates that the outer core behaves like a liquid, since transverse waves are unable to propagate in a liquid medium. It is believed that the outer core consists of molten iron having a density of 8 to 10 g/cm 3 . The inner core has a radius of approx. 1350 km is considered as a rigid body, because the speed of propagation of seismic waves in it again increases sharply. The inner core appears to consist almost entirely of the very high-density elements iron and nickel. See also geology.
Hydrosphere represents the totality of all natural waters on and near the earth's surface. Its mass is less than 0.03% of the mass of the entire Earth. Almost 98% of the hydrosphere is made up of salty waters of oceans and seas, covering approx. 71% of the earth's surface. About 4% comes from continental ice, lake, river and groundwater; some water is contained in minerals and living nature.
Four oceans (Pacific - the largest and deepest, occupying almost half of the earth's surface, Atlantic, Indian and Arctic) together with the seas form a single water area - the World Ocean. However, the oceans are not evenly distributed on Earth and vary greatly in depth. In some places, the oceans are separated only by a narrow strip of land (for example, the Atlantic and Pacific - the Isthmus of Panama) or shallow water straits (for example, the Bering Strait - the Arctic and Pacific oceans). The underwater continuation of the continents are rather shallow continental shelves, occupying large areas off the coast of North America, eastern Asia and northern Australia and gently sloping towards the open ocean. The shelf edge (edge) usually ends abruptly at the transition to the continental slope, which initially drops steeply and then gradually flattens in the zone of the continental foot, which gives way to a deep-sea bed with average depths of 3700–5500 m. The continental slope is usually cut by deep submarine canyons, often marine continuation of large river valleys. River sediments are carried through these canyons and form submarine fans on the continental foot. Only the finest clay particles reach the deep-sea abyssal plains. The ocean floor has an uneven surface and is a combination of underwater plateaus and mountain ranges, in places topped by volcanic mountains (flat-topped seamounts are called guyots). In tropical seas, seamounts culminate in ring-shaped coral reefs that form atolls. Along the periphery of the Pacific Ocean and along the young island arcs of the Atlantic and Indian Oceans there are trenches more than 11 km deep.
Sea water is a solution containing on average 3.5% minerals (its salinity is usually expressed in ppm, ‰). The main component of sea water is sodium chloride; magnesium chloride and sulfate, calcium sulfate, sodium bromide, etc. are also present. Some inland seas, due to the influx of huge quantities fresh water have less high salinity (for example, the maximum salinity of the Baltic Sea is 11‰), while other inland seas and lakes have very high salinity (Dead Sea - 260–310‰, Great Salt Lake - 137–300‰).
Atmosphere- the air shell of the Earth, consisting of five concentric layers - the troposphere, stratosphere, mesosphere, thermosphere and exosphere. There is no real upper boundary of the atmosphere. The outer layer, starting at approximately 700 km altitude, gradually thins out and passes into interplanetary space. In addition, there is also a magnetosphere that penetrates all layers of the atmosphere and extends far beyond its limits.
The atmosphere consists of a mixture of gases: nitrogen (78.08% of its volume), oxygen (20.95%), argon (0.9%), carbon dioxide (0.03%) and rare gases - neon, helium, krypton and xenon (total 0.01%). Water vapor is present almost everywhere near the earth's surface. In the atmosphere of cities and industrial areas, increased concentrations of sulfur dioxide, carbon dioxide and carbon monoxide, methane, carbon fluoride and other gases of anthropogenic origin are found. See also air pollution.
Troposphere – layer of the atmosphere in which weather occurs. In temperate latitudes it extends to approximately 10 km altitude. Its upper limit, known as the tropopause, is higher at the equator than at the poles. There are also seasonal changes– in summer the tropopause is located slightly higher than in winter. Within the tropopause, huge masses of air circulate. The average air temperature in the surface layer of the atmosphere is approx. 15° C. With altitude, the temperature decreases by about 0.6° for every 100 m of altitude. Cold air upper layers the atmosphere falls, and the warm atmosphere rises. But under the influence of the rotation of the Earth around its axis and local features The distribution of heat and moisture, this fundamental scheme of atmospheric circulation, is undergoing changes. Most solar thermal energy enters the atmosphere in the tropics and subtropics, from where, as a result of convection, warm air masses are transported to high latitudes, where they lose heat. See also METEOROLOGY AND CLIMATOLOGY.
Stratosphere located in the range from 10 to 50 km above sea level. It is characterized by fairly constant winds and temperatures (on average about -50° C) and rare pearlescent clouds formed by ice crystals. However, in the upper layers of the stratosphere, temperatures rise. Strong turbulent currents of air, known as jet streams, circulate around the Earth at polar latitudes and at equatorial belt. Depending on the direction of travel of jet aircraft flying in the lower stratosphere, jet streams may pose a hazard or be conducive to flight. In the stratosphere, solar ultraviolet radiation and charged particles (mainly protons and electrons) interact with oxygen, producing ozone, oxygen and nitrogen ions. The highest ozone concentrations are found in the lower stratosphere.
Mesosphere– a layer of the atmosphere located in the altitude range from 50 to 80 km. Within its limits, the temperature gradually decreases from approximately 0 ° C at the lower limit to –90 ° C (sometimes to –110 ° C) at the upper limit - mesopause. Associated with the middle layers of the mesosphere is the lower boundary of the ionosphere, where electromagnetic waves are reflected by ionized particles.
The region between 10 and 150 km is sometimes called the chemosphere because it is here, mainly in the mesosphere, that photochemical reactions occur.
Thermosphere– high layers of the atmosphere from approximately 80 to 700 km, in which the temperature rises. Since the atmosphere here is rarefied, the thermal energy of the molecules - mainly oxygen - is low, and temperatures depend on the time of day, solar activity and some other factors. At night, temperatures range from approximately 320°C during periods of minimum solar activity to 2200°C during peak solar activity.
Exosphere – the uppermost layer of the atmosphere, starting at altitudes of approx. 700 km, where atoms and molecules are so far from each other that they rarely collide. This is the so-called critical level, in which the atmosphere ceases to behave like an ordinary gas, and atoms and molecules move in the Earth's gravitational field like satellites. In this layer, the main components of the atmosphere are hydrogen and helium - light elements that ultimately escape into outer space.
The Earth's ability to hold an atmosphere depends on the strength of gravity and the speed of air molecules. Any object that moves away from the Earth at a speed of less than 8 km/s returns to it under the influence of gravity. At a speed of 8–11 km/s, the object is launched into low-Earth orbit, and above 11 km/s it overcomes Earth’s gravity.
Many particles in the upper atmosphere that have high energy, could quickly evaporate into outer space if they were not captured by the Earth’s magnetic field (magnetosphere), which protects all living organisms (including humans) from the harmful effects of low-intensity cosmic radiation. See also atmosphere;interstellar matter; space exploration and use.
GEODYNAMICS
Movements of the earth's crust and the evolution of continents. The main changes in the face of the Earth consist of mountain formation and changes in the area and outlines of continents, which rise and fall during formation. For example, the Colorado Plateau with an area of ​​647.5 thousand km 2, once located at sea level, currently has average absolute altitudes OK. 2000 m, and the Tibetan Plateau with an area of ​​​​approx. 2 million km 2 rose approximately 5 km. Such land masses could rise at a speed of approx. 1 mm/year. After mountain building ends, destructive processes begin to operate, mainly water and, to a lesser extent, wind erosion. Rivers continuously erode rocks and deposit sediments downstream. For example, the Mississippi River annually carries approx. 750 million tons of dissolved and solid sediments.
The continental crust is composed of relatively lightweight material, therefore, continents, like icebergs, float in the dense plastic mantle of the Earth. At the same time, the lower, most part of the mass of the continents is located below sea level. The earth's crust is most deeply immersed in the mantle in the region mining structures, forming the so-called "roots" of the mountains. When mountains are destroyed and weathering products are removed, these losses are compensated by new “growth” of the mountains. On the other hand, the overload of river deltas with incoming debris is the reason for their constant subsidence. Such maintenance equilibrium state The parts of continents submerged below sea level and located above it are called isostasy.
Earthquakes and volcanic activity. As a result of movements of large blocks of the earth's surface, faults form in the earth's crust and folding occurs. A giant global system of faults and faults, known as the mid-ocean rift, encircles the Earth for more than 65 thousand km. This rift is characterized by movement along faults, earthquakes, and a strong flow of internal thermal energy, which indicates that magma is located near the Earth's surface. The San Andreas fault in southern California also belongs to this system, within which during earthquakes individual blocks of the earth's surface are displaced by up to 3 m vertically. Pacific " fire ring" and the Alpine-Himalayan mountain belt are the main areas of volcanic activity associated with the mid-ocean rift. Almost 2/3 of the known approximately 500 volcanoes are confined to the first of these areas. This is where approx. 80% of all earthquakes on Earth. Sometimes new volcanoes appear before our eyes, such as the Paricutin volcano in Mexico (1943) or Surtsey in southern shores Iceland (1965).
Earth tides. Of a completely different nature are periodic deformations of the Earth with an average amplitude of 10–20 cm, known as earth tides, partially caused by the attraction of the Earth by the Sun and Moon. In addition, the points in the sky at which the Moon's orbit intersects the plane of the Earth's orbit orbit the Earth with a period of 18.6 years. This cycle affects the state of the “solid” Earth, atmosphere and ocean. By increasing the height of tides on continental shelves, it can stimulate strong earthquakes and volcanic eruptions. In temperate latitudes, this can lead to an increase in the speed of some ocean currents, such as the Gulf Stream and Kuroshio. Then their warm waters will have a more significant influence on the climate. See also ocean currents; ocean ; MOON ; ebbs and flows.
Continental drift. Although most geologists believed that the formation of faults and folding occurred on land and on the bottom of the oceans, it was believed that the position of the continents and ocean basins was strictly fixed. In 1912, the German geophysicist A. Wegener suggested that ancient land masses were splitting into pieces and drifting like icebergs on a more plastic oceanic crust. Then this hypothesis did not find support among most geologists. However, as a result of studies of deep-sea basins in the 1950–1970s, irrefutable evidence was obtained in favor of Wegener's hypothesis. Currently, the theory of plate tectonics forms the basis of ideas about the evolution of the Earth.
Ocean floor spreading. Deep-sea magnetic surveys of the ocean floor have shown that ancient volcanic rocks are covered by a thin mantle of river sediment. These volcanic rocks, mainly basalts, retained information about the geomagnetic field as they cooled during the Earth's evolution. Since, as mentioned above, the polarity of the geomagnetic field changes from time to time, basalts formed in different eras, have magnetization opposite sign. The ocean floor is divided into strips made of rocks that differ in the sign of magnetization. The parallel stripes located on either side of the mid-ocean ridges are symmetrical in width and direction of magnetic field strength. The youngest formations are located closest to the ridge crest, since they represent freshly erupted basaltic lava. Scientists believe that hot molten rocks rise up along cracks and spread on both sides of the ridge axis (this process can be compared to two conveyor belts moving in opposite directions), and stripes with opposite magnetization alternate on the surface of the ridges. The age of any such strip of seabed can be determined with great accuracy. These data are considered as reliable evidence in favor of spreading (expansion) of the ocean floor.
Plate tectonics. If the ocean floor is expanding at the suture zone of a mid-ocean ridge, this means that either the Earth's surface is increasing or there are areas where the oceanic crust is disappearing and sinking into the asthenosphere. Such areas, called subduction zones, have indeed been found in a belt bordering the Pacific Ocean and in a discontinuous strip stretching from Southeast Asia to the Mediterranean. All these zones are confined to deep-sea trenches encircling island arcs. Most geologists believe that on the surface of the Earth there are several rigid lithospheric plates that “float” on the asthenosphere. Plates can slide past one another, or one can sink beneath another in a subduction zone. A unified plate tectonics model provides the best explanation for the distribution of large geological structures and zones of tectonic activity, as well as changes relative position continents.
Seismic zones. Mid-ocean ridges and subduction zones are belts of frequent strong earthquakes and volcanic eruptions. These areas are connected by long linear faults that can be traced across the globe. Earthquakes are confined to faults and very rarely occur in any other areas. Towards the continents, the epicenters of earthquakes are located deeper and deeper. This fact explains the mechanism of subduction: an expanding oceanic plate dives under volcanic belt at an angle of approx. 45°. As it “slides,” the oceanic crust melts into magma, which flows through cracks as lava to the surface.
Mountain building. Where ancient ocean basins are destroyed by subduction, continental plates collide with each other or with fragments of plates. As soon as this happens, the earth's crust is greatly compressed, a thrust is formed, and the thickness of the crust almost doubles. Due to isostasy, the folded zone experiences uplift and thus mountains are born. The belt of mountain structures of the Alpine stage of folding can be traced along the Pacific coast and in the Alpine-Himalayan zone. In these areas, numerous collisions of lithospheric plates and uplift of the territory began ca. 50 million years ago. More ancient mountain systems, such as the Appalachians, are over 250 million years old, but at present they are so destroyed and smoothed that they have lost their typical mountain appearance and turned into an almost flat surface. However, since their "roots" are embedded in the mantle and float, they have experienced repeated uplift. And yet, over time, such ancient mountains will turn into plains. Majority geological processes They go through the stages of youth, maturity and old age, but usually this cycle takes a very long time.
Distribution of heat and moisture. The interaction of the hydrosphere and the atmosphere controls the distribution of heat and moisture on the earth's surface. The relationship between land and sea largely determines the nature of the climate. When the land surface increases, cooling occurs. The uneven distribution of land and sea is currently a prerequisite for the development of glaciation.
The Earth's surface and atmosphere receive the most heat from the Sun, which emits thermal and light energy with almost the same intensity throughout the existence of our planet. The atmosphere prevents the Earth from returning this energy too quickly back into space. About 34% of solar radiation is lost due to reflection by clouds, 19% is absorbed by the atmosphere and only 47% reaches the earth's surface. The total influx of solar radiation to upper limit atmosphere is equal to the release of radiation from this boundary into outer space. As a result, the thermal balance of the Earth-atmosphere system is established.
The land surface and ground air quickly heat up during the day and lose heat quite quickly at night. If there were no heat-trapping layers in the upper troposphere, the amplitude of daily temperature fluctuations could be much greater. For example, the Moon receives about the same amount of heat from the Sun as the Earth, but because the Moon has no atmosphere, its surface temperatures rise to about 101°C during the day and drop to -153°C at night.
The oceans, whose water temperature changes much more slowly than the temperature of the earth's surface or air, have a strong moderating effect on the climate. At night and in winter, air over the oceans cools much more slowly than over land, and if oceanic air masses move over continents, this leads to warming. Conversely, during the day and summer the sea breeze cools the land.
The distribution of moisture on the earth's surface is determined by the water cycle in nature. Every second, huge amounts of water evaporate into the atmosphere, mainly from the surface of the oceans. Moist oceanic air, sweeping over the continents, cools. The moisture then condenses and returns to the earth's surface in the form of rain or snow. It is partially preserved in snow cover, rivers and lakes, and partially returns to the ocean, where evaporation occurs again. This completes the hydrological cycle.
Ocean currents are the Earth's powerful thermoregulatory mechanism. Thanks to them, uniform, moderate temperatures are maintained in tropical ocean areas and warm waters are transported to colder high-latitude regions.
Since water plays a significant role in erosion processes, it thereby affects the movements of the earth's crust. And any redistribution of masses caused by such movements under the conditions of the Earth rotating around its axis can, in turn, contribute to a change in the position of the Earth’s axis. During ice ages Sea levels are falling as water accumulates in glaciers. This, in turn, leads to the expansion of continents and increased climatic contrasts. Reduced river flows and lower sea levels prevent warm temperatures from reaching ocean currents cold regions, leading to further climate changes.
EARTH MOVEMENT
The Earth rotates on its axis and revolves around the Sun. These movements are complicated by the gravitational influence of other objects in the Solar System, which is part of our Galaxy (Fig. 6). The galaxy rotates around its center, therefore, the solar system, along with the Earth, is involved in this movement.
Rotation around its own axis. The Earth makes one revolution around its axis in 23 hours 56 minutes 4.09 seconds. The rotation occurs from west to east, i.e. counterclockwise (as viewed from the North Pole). Therefore, the Sun and Moon appear to rise in the east and set in the west. The Earth makes approximately 365 1/4 revolutions during one revolution around the Sun, which is one year or takes 365 1/4 days. Since for each such revolution, in addition to a whole day, an additional quarter of a day is spent, every four years one day is added to the calendar. The Moon's gravitational pull gradually slows down the Earth's rotation and lengthens the day by about 1/1000th of a second every century. According to geological data, the rate of rotation of the Earth could change, but not by more than 5%.
The Earth's revolution around the Sun. The Earth revolves around the Sun in an elliptical orbit, close to circular, in the direction from West to East at a speed of approx. 107,000 km/h. The average distance to the Sun is 149,598 thousand km, and the difference between the largest and smallest distance is 4.8 million km. The eccentricity (deviation from the circle) of the Earth's orbit changes very little over a cycle lasting 94 thousand years. Changes in the distance to the Sun are believed to contribute to the formation of a complex climate cycle, the individual stages of which are associated with the advance and retreat of glaciers during ice ages. This theory, developed by the Yugoslav mathematician M. Milankovic, is confirmed by geological data.
The Earth's rotation axis is inclined to the orbital plane at an angle of 66°33", due to which the seasons change. When the Sun is above the Tropic of the North (23°27" N), summer begins in the Northern Hemisphere, while the Earth is located farthest from the Sun. In the Southern Hemisphere, summer begins when the Sun rises above Southern Tropic(23°27" S). At this time, winter begins in the Northern Hemisphere.
Precession. The attraction of the Sun, Moon and other planets does not change the angle of inclination of the earth's axis, but causes it to move along circular cone. This movement is called precession. Currently North Pole directed towards the North Star. A complete precession cycle is approx. 25,800 years and makes a significant contribution to the climate cycle that Milanković wrote about.
Twice a year, when the Sun is directly above the equator, and twice a month, when the Moon is similarly positioned, the attraction that causes precession is reduced to zero and a periodic increase and decrease in the rate of precession occurs. This oscillatory motion of the earth's axis is known as nutation, which peaks every 18.6 years. This periodicity ranks second in influence on climate after the change of seasons.
The Earth-Moon system. Earth and Moon connected mutual attraction. The overall center of gravity, called the center of mass, is located on a line connecting the centers of the Earth and the Moon. Since the Earth's mass is almost 82 times that of the Moon, the center of mass of this system is located at a depth of more than 1600 km from the Earth's surface. Both the Earth and the Moon orbit this point in 27.3 days. As they orbit the Sun, the center of mass describes a smooth ellipse, although each of these bodies has a wavy trajectory.
Other forms of movement. Within the Galaxy, the Earth and other objects of the Solar System move at a speed of approx. 19 km/s in the direction of the star Vega. In addition, the Sun and other neighboring stars orbit the galactic center at a speed of approx. 220 km/s. In turn, our Galaxy is part of a small local group of galaxies, which, in turn, is part of a giant cluster of galaxies.
LITERATURE
Magnitsky V.A. Internal structure and physics of the Earth. M., 1965
Vernadsky V.I.

Earth is the third planet from the Sun. The largest planet of the terrestrial group in terms of density, diameter, mass. Of all the known planets, only Earth has an oxygen-containing atmosphere and a large amount of water in a liquid state. The only one known to man a planet on which there is life.

Brief description

The Earth is the cradle of humanity, a lot is known about this planet, but still, all its secrets are at the modern level scientific development we can't figure it out. Our planet is quite small on the scale of the Universe, mass 5.9726 * 10 24 kg, has the shape of a non-ideal ball, its average radius is 6371 km, equatorial radius - 6378.1 km, polar radius - 6356.8 km. Circumference great circle at the equator it is 40,075.017 km, and at the meridian it is 40,007.86 km. The volume of the Earth is 10.8 * 10 11 km 3.

The center of rotation of the Earth is the Sun. The movement of our planet occurs within the ecliptic. Rotates in an orbit formed at the beginning of the formation of the solar system. The shape of the orbit is represented as an imperfect circle, the distance from the sun in January is 2.5 million km closer than in June, the average distance from the Sun is considered to be 149.5 million km (astronomical unit).

The Earth rotates from west to east, but the axis of rotation and the equator are tilted relative to the ecliptic. The Earth's axis is not vertical, it is inclined at an angle of 66 0 31’ relative to the ecliptic plane. The equator is inclined at 23 0 relative to the Earth's axis of rotation. The Earth's rotation axis does not constantly change due to precession; this change is influenced by the gravitational force of the Sun and Moon, the axis describes a cone around its neutral position, the precession period is 26 thousand years. But in addition to this, the axis also experiences vibrations called nutation, since it cannot be said that only the Earth rotates around the sun, because the Earth-Moon system rotates, they are connected to each other in the form of a dumbbell, the center of gravity of which, called the barycenter, is located inside The Earth is at a distance from the surface of about 1700 km. Therefore, due to nutation, the oscillations superimposed on the precession curve amount to 18.6 thousand years, i.e. The angle of inclination of the earth's axis is relatively constant for a long time, but undergoes minor changes with a periodicity of 18.6 thousand years. The rotation time of the Earth and the entire solar system around the center of our galaxy, the Milky Way, is 230-240 million years (galactic year).

The average density of the planet is 5.5 g/cm 3 , on the surface the average density is about 2.2-2.5 g/cm 3 , the density inside the Earth is high, its growth occurs spasmodically, the calculation is made according to the period free vibrations, moment of inertia, moment of impulse.

Most of the surface (70.8%) is occupied by the World Ocean, the rest is continents and islands.

Gravity acceleration, at ocean level at latitude 45 0: 9.81 m/s 2 .

Earth is a terrestrial planet. Terrestrial planets are characterized by high density and consist predominantly of silicates and metallic iron.

The Moon is the only natural satellite of the Earth, but there are also a huge number of artificial satellites in orbit.

Education of the planet

The Earth was formed by the accretion of a planetesimal about 4.6 billion years ago. Planetesimals are particles that stick together in a gas and dust cloud. The process of particles sticking together is accretion. The process of contraction of these particles occurred very quickly; for the life of our Universe, several million years are considered an instant. After 17-20 million years from the beginning of formation, the Earth gained the mass of modern Mars. After 100 million years, the Earth has gained 97% of its modern mass.

Initially, the Earth was molten and hot due to strong volcanism and frequent collisions with other celestial bodies. Gradually, the outer layer of the planet cooled and turned into the Earth's crust, which we can now observe.

It is believed that the Moon was formed due to the impact of a celestial body on the surface of the Earth, the mass of which was about 10% of the Earth's mass, as a result of which part of the substance was thrown into near-Earth orbit. Soon the Moon was formed from this material, at a distance of 60 thousand km. As a result of the impact, the Earth received a large impulse, which led to a period of revolution around its axis of 5 hours, and a noticeable tilt of the rotation axis also appeared.

Degassing and volcanic activity created the first atmosphere on Earth. It is assumed that water, i.e. ice and water vapor were carried by comets colliding with the Earth.

Over hundreds of millions of years, the surface of the planet was constantly changing, continents formed and broke apart. They moved along the surface, uniting and forming a continent. This process occurred cyclically. Around 750 million years ago, the earliest known supercontinent Rodinia began to break up. Later, from 600 to 540 million years ago, the continents formed Pannotia and finally Pangea, which broke up 180 million years ago.

We do not have an accurate idea of ​​the age and formation of the Earth; all this data is indirect.

The first photograph taken by Explorer 6.

Observation

Shape and internal structure of the Earth

Planet Earth has 3 different axes: equator, polar and equatorial radii, structurally it is a cardioidal ellipsoid, it has been calculated that the polar regions are slightly elevated in relation to other regions and resemble the shape of a heart, Northern Hemisphere raised 30 meters relative to southern hemisphere. Polar asymmetry of the structure is observed, but nevertheless we believe that the Earth has the shape of a spheroid. Thanks to satellite studies, it was revealed that the Earth has depressions on its surface and a picture of the Earth was presented in the form of a pear, that is, it is a triaxial ellipsoid of rotation. The difference between the geoid and the triaxial ellipsoid is no more than 100 m, this is due to uneven distribution masses both on the surface of the Earth (oceans and continents) and inside it. At each point on the surface of the geoid, the force of gravity is directed perpendicular to it and is an equipotential surface.

The main method for studying the structure of the Earth is the seismological method. The method is based on the study of changes in the velocities of seismic waves depending on the density of matter inside the Earth.

The earth has a layered internal structure. It consists of hard silicate shells (crust and viscous mantle) and a metallic core. The outer part of the core is liquid, and the inner part is solid. The structure of the planet is similar to a peach:

• thin crust - the earth's crust, average thickness 45 km (from 5 to 70 km), greatest thickness under large mountains;
• layer of the upper mantle (600 km), contains a layer that differs in physical characteristics(decrease in the speed of seismic waves), in which the substance is either heated or slightly melted - a layer called the asthenosphere (50-60 km under the oceans and 100-120 km under the continents).

The part of the Earth that is located together with the earth's crust and the upper part of the mantle, up to the asthenosphere layer, is called the Lithosphere.

1. The boundary between the upper and lower mantle (depth 660 km), the boundary becomes more and more clear and sharp every year, the thickness is 2 km, the wave speed and composition of the substance changes on it.
2. The lower mantle reaches a depth of 2700 - 2900 km, thanks to Russian scientists it has been established that there may be another boundary in the lower mantle, i.e. existence of the middle mantle.
3. The outer core is a liquid substance (depth 4100 km), which does not transmit transverse waves; it is not necessary that this part has the appearance of some kind of liquid, this substance simply has the characteristics of a liquid object.
4. The inner core is solid, iron with nickel impurities (Fe: 85.5%; Ni: 5.20%), depth 5150 - 6371 km.

All data were obtained indirectly, since wells were not drilled to such a depth, but they are theoretically proven.

The force of gravity at any point on the earth depends on Newtonian gravity, but the placement of density inhomogeneities is important, which explains the inconstancy of gravity. There is an effect of isostasy (balancing), the higher the mountain, the larger the root of the mountain. A striking example of the isostasy effect is an iceberg. There is a paradox in the North Caucasus, there is no balancing, why this happens is still not known.

Earth's atmosphere

The atmosphere is the gaseous shell surrounding the Earth. Conventionally, it borders on interplanetary space at a distance of 1300 km. It is officially believed that the boundary of the atmosphere is determined at an altitude of 118 km, that is, above this distance, aeronautics becomes completely impossible.

Air mass (5.1 - 5.3)*10 18 kg. The air density at the sea surface is 1.2 kg/m3.

The appearance of the atmosphere is determined by two factors:

• Evaporation of matter cosmic bodies when they fall to Earth.
• Degassing of the earth's mantle is the release of gas during volcanic eruptions.

With the emergence of the oceans and the advent of the biosphere, the atmosphere began to change due to gas exchange with water, plants, animals and the products of their decomposition in soils and swamps.

Atmospheric structure:

1. The planetary boundary layer is the lowest layer of the gaseous shell of the planet, the properties and characteristics of which are largely determined by the interaction with the type of surface of the planet (liquid, solid). The thickness of the layer is 1-2 km.
2. The troposphere is the lower layer of the atmosphere, the most studied, and has different thicknesses at different latitudes: in the polar regions 8-10 km, in moderate latitudes 10-12 km, at the equator 16-18 km.
3. Tropopause is a transition layer between the troposphere and stratosphere.
4. The stratosphere is a layer of the atmosphere located at an altitude of 11 km to 50 km. A slight change in temperature in the initial layer with a subsequent increase in the layer 25 – 45 km from -56 to 0 0 C.
5. Stratopause is the boundary layer between the stratosphere and mesosphere. In the stratopause layer, the temperature remains at 0 0 C.
6. Mesosphere - the layer begins at an altitude of 50 km with a thickness of about 30-40 km. The temperature decreases by 0.25-0.3 0 C with an increase in altitude by 100 m.
7. Mesopause is a transition layer between the mesosphere and thermosphere. The temperature in this layer fluctuates at -90 0 C.
8. The thermosphere is the highest point of the atmosphere at an altitude of about 800 km. The temperature rises to altitudes of 200–300 km, where values ​​of the order of 1500 K are reached, then fluctuates within this limit with increasing altitude. The region of the ionosphere, the place where air ionization occurs (“aurora”) lies inside the thermosphere. The thickness of the layer depends on the level of solar activity.

There is a limit line that separates the Earth’s atmosphere and outer space, called the Karman Line. Altitude 100 km above sea level.

Hydrosphere

The total volume of water on the planet is about 1390 million km 3, it is not surprising that 72% of the total area of ​​the Earth is occupied by oceans. Oceans are a very important part of geological activity. The mass of the hydrosphere is approximately 1.46 * 10 21 kg - this is almost 300 times the mass of the atmosphere, but a very small fraction of the mass of the entire planet.

The hydrosphere is divided into the oceans, groundwater and surface water.

The deepest point in the World Ocean (Mariana Trench) is 10,994 meters, the average ocean depth is 3800 m.

Surface continental waters occupy only a small fraction of the total mass of the hydrosphere, but nevertheless play vital role in the life of the terrestrial biosphere, being the main source of water supply, irrigation and water supply. Moreover, this part of the hydrosphere is in constant interaction with the atmosphere and the earth's crust.

Water in a solid state is called the cryosphere.

The water component of the planet's surface determines the climate.

The earth is represented as a magnet, approximated by a dipole (northern and southern polis). At the north pole the force lines go in, and at the south they go out. In fact, there should be a south pole at the north (geographical) pole, and there should be a north pole at the south (geographical) pole, but it was agreed the other way around. The Earth's rotation axis and the geographic axis do not coincide; the difference in the center of the divergence is about 420-430 km.

The Earth's magnetic poles are not in one place; they are constantly shifting. At the equator, the Earth's magnetic field has an induction of 3.05 10 -5 T and magnetic moment 7.91 10 15 T m 3 . The magnetic field strength is not high, for example, the magnet on the cabinet door is 30 times stronger.

Based on the residual magnetization, it was clear that the magnetic field changed its sign many times, several thousand.

The magnetic field forms a magnetosphere, which delays harmful radiation Sun.

The origin of the magnetic field remains a mystery to us, there are only hypotheses, they are that our Earth is a magnetic hydrodynamo. For example, Mercury has no magnetic field.

The time when the magnetic field appeared also remains a problem; it is known that it was 3.5 billion years ago. But more recently, evidence has emerged that in zircon minerals found in Australia, which are 4.3 billion years old, there remains a remanent magnetization, which remains a mystery.

The deepest place on Earth was discovered in 1875 - the Mariana Trench. Deepest point 10,994.

The highest point is Everest, Chomolungma - 8848 meters.

On the Kola Peninsula, 10 km west of the city of Zapolyarny, the most deep well in the world. Its depth is 12,262 meters.

Is there a point on our planet where we will weigh less than a mosquito? Yes, there is, the center of our planet, power gravitational attraction there is equal to 0, thus, the weight of a person in the center of our planet is less than the weight of any insect on the surface of the Earth.

One of the most beautiful phenomena observed with the naked eye is the aurora - the glow of the upper layers of the planet’s atmosphere, which have a magnetosphere, due to their interaction with charged particles of the solar wind.

Antarctica contains 2/3 fresh water reserves.

If all the glaciers melt, the water level will rise by about 900 meters.

Hundreds of thousands of tons of cosmic dust fall on us every day, but almost everything burns up in the atmosphere.

The most studied planet in the solar system is our home planet - Earth. Currently, this is the only known space object in the solar system inhabited by living organisms. In a word, the Earth is our home.

History of the planet

Estimated scientists planet The earth was formed approximately 4.5 billion years ago, and the first forms of life only 600 million years later. A lot has changed since then. Living organisms created a global ecosystem; the magnetic field, together with the ozone layer, protected them from harmful cosmic radiation. All this and many other factors made it possible to create the most beautiful and “living” planet in the solar system.

10 things you need to know about Earth!

1. Earth in the solar system is the third planet from the suns A;
2. Our planet revolves around one natural satellite - the Moon;
   
3. Earth is the only planet not named after a divine being;
4. The Earth's density is the greatest of all the planets in the solar system;
5. The Earth's rotation speed is gradually slowing down;
6. The average distance from the Earth to the Sun is 1 astronomical unit(a conventional measure of length in astronomy), which equals approximately 150 million km;
7. The Earth has a magnetic field of sufficient strength to protect living organisms on its surface from harmful solar radiation;
8. First artificial satellite Earth called PS-1 (The simplest satellite - 1) was launched from the Baikonur Cosmodrome on the Sputnik launch vehicle on October 4, 1957;
9. In orbit around the Earth, compared to other planets, there is the largest number of spacecraft;
10. Earth is the largest terrestrial planet in the solar system;

Astronomical characteristics

The meaning of the name of planet Earth

The word Earth is very old, its origin is lost in the depths of Proto-Indo-European language community. Vasmer's dictionary provides links to similar words in Greek, Persian, Baltic, and also, naturally, in Slavic languages, where the same word is used (in accordance with phonetic laws specific languages) with the same meaning. The original root has the meaning "low". Previously, it was believed that the earth was flat, “low,” and rested on three whales, elephants, turtles, etc.

Physical characteristics of the Earth

Rings and satellites

One natural satellite, the Moon, and more than 8,300 artificial satellites orbit the Earth.

Features of the planet

Earth is our home planet. It is the only planet in our solar system where life definitely exists. Everything we need to survive is hidden under thin layer an atmosphere that separates us from the desolate and uninhabitable space as we know it. The Earth is made up of complex interactive systems that are often unpredictable. Air, water, land, life forms, including humans, join forces to create the ever-changing world that we strive to understand.

Exploring the Earth from space allows us to look at our planet as a whole. Scientists from all over the world, working together and sharing their experiences, have discovered many interesting facts about our planet through this opportunity.

Some facts are well known. For example, Earth is the third planet from the Sun and the fifth largest in the Solar System. The diameter of the Earth is only a few hundred kilometers larger than that of Venus. The four seasons are the result of a tilt of the Earth's axis of rotation of more than 23 degrees.

Oceans, with an average depth of 4 kilometers, occupy almost 70% of the earth's surface. Clean water exists in liquid phase only in a narrow temperature range (from 0 to 100 degrees Celsius). This temperature range is especially small compared to the temperature spectrum that is present on other planets in the solar system. The presence and distribution of water vapor in the atmosphere is largely responsible for the formation of weather on Earth.

Our planet has at its center a rapidly rotating molten core consisting of nickel and iron. It is thanks to its rotation that a magnetic field is formed around the Earth, protecting us from solar wind, turning it into auroras.

Atmosphere of the planet

Near the surface of the Earth there is a huge ocean of air - our atmosphere. It consists of 78% nitrogen, 21% oxygen and 1% other gases. Thanks to this air gap, which protects us from what is destructive for all living space, a variety of weather conditions are formed on Earth. It is this that protects us from harmful solar radiation and falling meteors. Space research vehicles have been studying our gaseous shell for half a century, but it has not yet revealed all the secrets.

The Earth is the object of study for a significant amount 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 describes the relief features of the planet's surface - oceans, seas, lakes and waters, 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) with 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. The inclination of the earth's axis to the ecliptic plane 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 the change of day and night, and the tilt of the axis and revolution around the Sun causes a change of times year.

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. The surface area of ​​the globe is 510 million km², volume - 1.083 10 12 km², average density - 5518 kg / m³. The mass of the Earth is 5976.10 21 kg. The earth has a magnetic field and a closely related electric field. The Earth's gravitational field determines its close to spherical shape and the existence of an atmosphere.

According to modern cosmogonic concepts, the Earth was formed approximately 4.7 billion years ago from scattered material in the protosolar system gaseous substance. As a result of differentiation of the Earth's substance, under the influence of its gravitational field, in conditions of heating of the earth's interior, various types arose and developed. chemical composition, state of aggregation and physical properties shells - geosphere: core (in the center), mantle, crust, hydrosphere, atmosphere, magnetosphere. The composition of the Earth is dominated by iron (34.6%), oxygen (29.5%), silicon (15.2%), magnesium (12.7%). Earth's crust, mantle and inner part the kernels are solid (the outer part of the kernel is considered liquid). From the surface of the Earth towards the center, pressure, density and temperature increase. The pressure at the center of the planet is 3.6 10 11 Pa, the density is approximately 12.5 10 ³ kg/m ³, and the temperature ranges from 5000 to 6000 °C. The main types of the earth's crust are continental and oceanic, in transition zone From the continent to the ocean, a crust of intermediate structure is developed.

Shape of the Earth

The figure of the Earth is an idealization that is used to try to describe the shape of the planet. Depending on the purpose of the description, use various models shapes of the Earth.

First approximation

The roughest form of description of the figure of the Earth at the first approximation is a sphere. For most problems general geoscience this approximation seems sufficient to be used in the description or study of certain geographical processes. In this 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 meridians, which characteristically distinguishes it from the infinity of sets of symmetry of an ideal sphere. The horizontal structure of the geographic envelope is characterized by a certain zonality and a certain symmetry relative to the equator.

Second approximation

At a closer approach, the figure of the Earth is equated to an ellipsoid of revolution. This model, characterized by a pronounced axis, an equatorial plane of symmetry and meridional planes, is used in geodesy for calculating coordinates, constructing cartographic networks, calculations, etc. The difference between the semi-axes 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 easily be theoretically calculated, 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 semi-axes of 200 m and an eccentricity of 1/30000, the third model is a triaxial ellipsoid. In geographical studies, this model is almost never used; it only indicates the complex internal structure of the planet.

Fourth approximation

The geoid is an equipotential surface that coincides with the average level of the World Ocean, is locus points in space that have the same gravitational 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. Practical significance and the 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

A general feature of the structure of the earth's surface is its distribution into continents and oceans. Most of the Earth is occupied by the World Ocean (361.1 million km² 70.8%), 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 sea level by an average of 875 m ( highest height 8848 m - Mount Chomolungma), mountains occupy over 1/3 of the land surface. Deserts cover approximately 20% of the land surface, forests - about 30%, glaciers - over 10%. The height amplitude on the planet reaches 20 km. The average depth of the world's oceans is approximately 3800 m ( greatest depth 11020 m - Mariana Trench (trench) in the 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 is thought to be 2,600 km in diameter and composed of pure iron or nickel, the outer core is 2,250 km thick of molten iron or nickel, and the mantle, about 2,900 km thick, is composed primarily of hard rock, separated from the crust by the Mohorovic surface. The crust and upper mantle form 12 main moving blocks, some of which support continents. Plateaus are constantly moving slowly, this movement is called tectonic drift.

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 differs in physical properties, condition and mineralogical composition. Depending on the magnitude of the velocities of seismic waves and the nature of their changes 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 distinguished in the Earth the lithosphere and the next, softened layer - the asthenosphere. Ball A, or the earth's crust, has a variable thickness (in the continental region - 33 km, in the oceanic region - 6 km, on average - 18 km).

The crust thickens under the mountains and almost disappears in the rift valleys of mid-ocean ridges. At the lower boundary of the earth's crust, the Mohorovicic surface, the velocities of seismic waves increase abruptly, which is mainly associated 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 Earth's core with a radius of 3486 km. At the border with the core (Gutenberg surface) the speed longitudinal waves sharply decreases by 30%, and transverse waves disappear, which means that the outer core (layer E, extends to a depth of 4980 km) is liquid. Below the transition layer F (4980-5120 km) there is a solid inner core (layer G), in which again transverse waves propagate.

The following chemical elements predominate in the solid 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: Po (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 sedimentation processes, the earth's crust is sharply differentiated; complex processes concentration and dispersion of chemical elements leading to the formation of various types of rocks.

It is believed that the upper mantle is close in composition to ultramafic rocks, dominated by O (42.5%), Mg (25.9%), Si (19.0%) and Fe (9.85%). In mineral terms, olivine reigns here, with fewer pyroxenes. The lower mantle is considered an analogue of stony meteorites (chondrites). The core of the earth 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, which is dominated by Fe (35%), A (30%), Si (15%) and Mg (13%).

Temperature is one of the the most important characteristics of the earth's interior, making 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 sources of volcanoes are located, the average temperature is slightly lower than the melting point 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 100-200 ° C higher than in the continents. The density of matter in layer C at 420 km corresponds to a pressure of 1.4 10 10 Pa and is identified with the 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 At about 4000 °C, silicates are in a solid state, and 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 Earth's atmosphere, 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. Maximum temperature land surface 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 living things from the harmful effects of cosmic radiation.

Chemical composition of the Earth's atmosphere: 78.1% - nitrogen, 20 - oxygen, 0.9 - argon, the rest - carbon dioxide, water vapor, hydrogen, helium, neon.

The 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. Phenomena that determine the weather occur in it. Due to the uneven heating of the Earth's surface by solar radiation, large masses of air constantly circulate in the troposphere. The main air currents in the Earth's atmosphere are the trade winds in a band of up to 30 ° along the equator and westerly winds temperate zone in the band from 30° to 60°. Another factor in heat transfer is the ocean current system.

Water has a constant cycle on the surface of the earth. Evaporating from the surface of waters and land, when favorable conditions water vapor rises in the atmosphere, leading 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 throughout the year.

Quantity solar energy, which the Earth's surface receives decreases with increasing latitude. The further from the equator, the smaller the angle of incidence of the sun's rays on the surface, and the greater the distance that the ray must travel in the atmosphere. As a consequence, the average 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 precipitation. The most widely recognized is the Köppen climate classification, which distinguishes five broad groups - humid tropics, desert, humid mid-latitudes, continental climate, cold polar climate. Each of these groups is divided into specific groups.

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, and hundreds of thousands of tons of lead into the atmosphere. Powerful producers of atmospheric emissions: thermal power plants, metallurgical, chemical, petrochemical, pulp and other industries, motor vehicles.

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, causing 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 atmospheric pollution appears more strongly. Important environmental problem Acid rain began to fall. Every year, when fuel is burned, up to 15 million tons of sulfur dioxide enters the atmosphere, which, when combined with water, forms a weak solution of sulfuric acid, which falls to the ground along with rain. Acid rain negatively affect people, crops, buildings, etc.

Ambient air pollution can also indirectly affect the health and sanitary living conditions of people.

The accumulation of carbon dioxide in the atmosphere can cause climate warming as a result of the greenhouse effect. Its essence is that the layer of carbon dioxide, which freely transmits 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 increase, which, in turn, will lead to the melting of glaciers, snow, rising levels of oceans and seas, and flooding of a significant part of the land.

Story

The Earth formed approximately 4540 million years ago from a disk-shaped protoplanetary cloud along with the other planets of the 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, and a thin solid shell formed on its surface - the earth's crust.

Shortly after the formation of the Earth, approximately 4530 million years ago, the Moon formed. Modern theory formation of a unified natural satellite 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 degassing of rocks and volcanic activity. Water condensed from the atmosphere to form the World Ocean. Despite the fact that the Sun by that time was 70% weaker than it is now, geological data shows that the ocean did not freeze, which may be due to the greenhouse effect. About 3.5 billion years ago, the Earth's magnetic field formed, protecting its atmosphere from the solar wind.

Earth Education and initial stage its development (lasting approximately 1.2 billion years) belongs to pre-geological history. The absolute age of the oldest rocks is over 3.5 billion years and, starting from this moment, counts down 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, life arose on Earth, 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 the 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 of man as a result of 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 further development noosphere - the shell of the Earth on which great influence exerts human activity.

High growth rate of the world population (number earth's population was 275 million in 1000, 1.6 billion in 1900 and approximately 6.7 billion in 2009) and the increasing influence of human society on the natural environment have raised problems rational use everyone natural resources and nature conservation.

Earth is a unique planet! Of course, this is true in our solar system and beyond. Nothing that scientists have observed leads to the idea that there are other planets like Earth.

Earth is the only planet orbiting our sun on which we know life exists.

Like no other planet, ours is covered with green vegetation, a vast blue ocean containing more than a million islands, hundreds of thousands of streams and rivers, vast masses of land called continents, mountains, glaciers and deserts that produce a wide variety of colors and textures.

Some forms of life can be found in almost every ecological niche on the surface of the Earth. Even in very cold Antarctica, hardy microscopic creatures thrive in ponds, tiny wingless insects live in patches of moss and lichen, plants grow and bloom annually. From the top of the atmosphere to the bottom of the oceans, from the cold part of the poles to the warm part of the equator, life flourishes. To this day, no signs of life have been found on any other planet.

The Earth is enormous in size, about 13,000 km in diameter, and weighing approximately 5.98 1024 kg. The Earth is on average 150 million km from the Sun. If the Earth goes much faster on its 584 million kilometer journey around the Sun, its orbit will become larger and it will move further away from the Sun. If she's too far from the narrow habitable zone, all life will cease to exist on Earth.

If this ride gets any slower in its orbit, the Earth will move closer to the Sun, and if it moves too close, all life will die as well. The Earth travels around the Sun in 365 days, 6 hours, 49 minutes and 9.54 seconds (a sidereal year), equivalent to more than a thousandth of a second!

If the average annual temperature on the Earth's surface changes by just a few degrees or so, most life on it will eventually become fried or frozen. This change will disrupt water-glacier relations and other important balances, with catastrophic results. If the Earth rotates slower than its axis, all life will die in time, either by freezing at night from lack of heat from the Sun or by burning during the day from too much heat.

Thus, our "normal" processes on Earth are undoubtedly unique among our Solar System, and, according to what we know, in the entire Universe:

1. It is a habitable planet. This the only planet in a solar system that supports life. All forms of life right from the smallest microscopic organisms to huge land and sea animals.

2. Its distance from the Sun (150 million kilometers) makes it reasonable to give it an average temperature of 18 to 20 degrees Celsius. It's not as hot as Mercury and Venus, nor as cold as Jupiter or Pluto.

3. It has an abundance of water (71%) that is not found on any other planet. And which is not found on any of the planets known to us in liquid state so close to the surface.

4. Has a biosphere that provides us with food, shelter, clothing and minerals.

5. Does not have poisonous gases like helium or methane as Jupiter.

6. It is rich in oxygen, which makes life on Earth possible.

7. Its atmosphere acts as a blanket of protection for the Earth from extreme temperatures.

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