General information about the Earth

Earth, the third largest planet from the Sun solar system. The earth belongs to a group of terrestrial planets, which also includes Mercury, Venus and Mars. Land is often compared with this group as well as with the Moon, since their origin, structure and evolution of the same. Due to its unique, perhaps, only in the universe of natural conditions (although this is doubtful), a place where there was and was developed by organic life.

  According to the modern cosmogonic notions Earth was formed about 4.566 billion years (plus or minus a few million) back from the dust cloud that originated in the sun. After analyzing the ratio of isotopes of hafnium and tungsten in the wreckage of the meteorites formed from cosmic dust from the Martian meteorites and terrestrial rocks, scientists have come to a new estimate (by about 60 million years old), consistent with computer models. "The formation of the nucleus, and hence planets similar to Earth, ending in the first 30 million years after the birth of the Solar System" - concluded Mr. Thorsten Klein, 30.08.2002 in Munich (Germany).

  Approximately 3.8 billion years ago, have conditions favorable for life. According to American researchers, the earliest known science downs of large meteorites on Earth has happened 3 billion 470 million years ago (with an error of no more than plus or minus 2 million years in age of zircon - one of the most persistent in the nature of minerals). It is estimated extraterrestrial had a diameter of about 20 miles and caused the young planet catastrophic destruction, including, apparently, even the cracks in the crust, which still divide it into tectonic plates. It is believed that the earth at that time was almost completely covered with water, and the only form of life on it were bacteria. Their further evolution of this cosmic catastrophe affected a little.

   For more later developed partial loss of life (about 380 (lost 40% of all inhabitants of the ocean), 251, 214 - Canada: the blow fell on the territory of modern Quebec, where there is still preserved crater with a diameter of 100 kilometers and 65 million years ago, more precisely the last studies give the age Chicxulub crater (Chicxulub) in Mexico, with a diameter of 180 km at 65.5 plus or minus 0.6 million years) due to the fact that meteorite fell to Earth (their diameters were about 6-12 km) and the effects were global in nature for the Earth. As a result, the second cataclysm, 90% of marine life and 70% of the animals were literally wiped off the face of our planet, and the latter has destroyed 75% of all living things and put an end to the era of dinosaurs (though can was a double blow on Earth, since the age of Meteor Crater Boltyshev in Ukraine whose diameter is 24 km dated at about 65.2 plus or minus 0.6 million years).

  The truth is the thought that perhaps the appearance of life on Earth after space disaster (asteroid, comet) that occurred 200 million years ago in the life of the Earth. Many scientists believe that Earth's history had to suffer several collisions with asteroids and after each cataclysm on to? Her world began to develop life, but then again almost complete "sterilization" of our planet. Especially in the early period of its development, had to deal with very large celestial bodies. Others, however, "The Stone Guest" - about a few kilometers in diameter - have contributed to heating of the earth's atmosphere up to 100 degrees Celsius. At the same pain? First part of the oceans after a collision with an asteroid evaporates, leaving? Ayasya water was almost boiling water. The only organisms Speaking as someone who? Them? Ansy survive after a disaster would have been the so-called high - ie, "heat resistant" bacteria. They are probably buried in the ground, and after the planet cooled a bit, began to actively proliferate. Subsequently, these microbes to mutate and give rise to new forms of life.

  A team of scientists led by Hans Keppler from the German University of Tuebingen believes that carbon emissions in the atmosphere in the form of carbon dioxide leads to the appearance of a gigantic scale? Tabah greenhouse effect, which causes uncontrolled warming of the planet. If carbon compounds will rise in the Earth's mantle at a depth of 40-60 km, there will be a process of decomposition, which leads to the output of carbon dioxide, which, through a crack in the earth's surface will penetrate the atmosphere. Similar phenomena accompany? Party or an abrupt change in the concentration of carbon dioxide in the atmosphere have already taken place at different times of the planet. So at the end of the Permian period, 245 million years ago, 96% of the inhabitants of the oceans and three-quarters of the living creatures on the su? E died. At a later period, about 208 million years ago, in late Triassic period, again unexpectedly lost half of living creatures on the planet.

   Several scientists believe that vspy? Ka close to the Earth supernova could lead to the destruction of life. ? Esearch layers with the age of 3 million years, and second - in the 4-6 million years, which included two hitherto unexplained cases of mass extinction of marine life forms, which are known to have appeared on the ground early? E land, showed that the natural iron-60 (radioactive isotope of iron) was formed under the influence of cosmic rays unusually high intensity, which suggests vspy? Re supernovae in a relatively young and close to the Sun, stellar subgroups. The result could be significantly damaged the ozone layer, which is why for? Her planet was vulnerable to extreme ultraviolet radiation from the sun. For example, according to specialists, vspy? Ka supernova at a distance of 130 light years from Earth, could lead to a decrease? Eniyu thickness of the ozone layer by 60% (But the latest assessment of Neil Gehrels of Goddard Space Flight Center show that in this case, the supernova must have exploded at a distance of no more than 25 light years). As a result, under the influence of UV light killed the pain? First part of marine plankton, followed by due to violation? Eniya food chain disappeared, and other marine organisms.

   One can not exclude the possibility of life on earth brought from out of space by meteorites (they are found not only organic substances but also sugar), as well, and water on the earth according to Louis Frank (Louis Frank) from the University? Tata Iowa, who claims that they found new evidence in support of his theory of the emergence of water on Earth is listed small? of comets, an abundance of billions of years ago, falling? them to Earth.

     In Earth's history there were several periods of global warming, the oldest of which occurred 135 million years ago. Sedimentary rocks are evidence of the former? Them in Earth's history previously unknown periods of global warming. One of the warming probably caused by methane, the product? Locally about 55 million years ago. It lasted about 200,000 years and caused the death of 30% to 50% of all forms of deep-ocean life, but it stimulated the emergence of new species at the surface.

     20 - 22.5 million years the Earth has changed its orbit and it has caused global climate change on? Her planet. After a sufficiently long period of warming and melting snows, when? Lo temporary cooling. This opinion specialists, University of California, led by James Zachosom (James Zachos). Hypothesis about the connection between the Earth's climate and changing the parameters of its orbit is not new [proposed in the 20-ies about? Logo century astrophysicist Milatinom Milankovitch (Milutin Milankovitch)]. But American experts managed to get some unexpected results. So it turned out that about 23 million years ago an? Locally match the minimum value of the eccentricity of Earth's orbit and the period of minimal changes in the inclination of the rotation axis of the Earth. Duration of the period amounted to 200 thousand years. ? Simultaneously in these years, terrestrial summer differed little from the earth of winter, and the difference in summer and winter temperatures at the poles is only a few degrees. Antarctic ice during the summer did not have time to melt and the product? Locally noticeable increase in their area.

    Astronomers at Johns Hopkins gathered together information from astronomy, geology and paleontology, conjectured that about 2 million years ago the Earth's ozone layer, which delays the ultraviolet radiation from the sun, literally blown off, taking into space. This has led to ecological catastrophe in Earth's oceans. Evidence of past elimination of ozone were found during drilling of the ocean floor. Then found a very unusual isotope of iron, which is probably the residue of the substance, which was BOAD? Jeno to Earth from a supernova explosion. But paleontologists have found that about 2 million years ago the product? Locally massive and could seemingly inexplicable extinction of phytoplankton and other marine organisms. Supernova explosion could occur as a result of:
          1) Close to the solar system (at a distance of 130 light-years), about 2 million years ago flew a star cluster Scorpius-Centaurus OB, containing thousands of large short-lived stars. This star cluster supernova explosions occurred quite frequently.
          2) The second candidate for the world's ozone killer - is the star Antares, which is located at a distance of 160 light-years away, but it was much further? E cluster Scorpius-Centaurus OB.
    . Homo sapiens («Homo sapiens) as a kind of came about about 2 million years ago, and the formation of the modern type of human product? Locally about 100 thousand years ago.

  Earth - the only one of the major planets, which is geologically active. Krupnomas? Tabnye parts of its surface appeared in the making, the relative motion, interaction and destruction? Eniya small? Th numbers (about ten) of the cortical plates that make up the lithosphere of the planet, which lies below the slide on the less rigid asthenosphere. Collision of plates cause the appearance of the mountains and on the plate boundaries are zones of seismic activity.
The Earth is the only moon-moon. Its orbit is close to a circle with a radius of about 384,400 km. But in addition there is another "partner" - an asteroid, 3753 (1986 TA) with the complex orbital relationship with Earth.

The shape, size and motion of the Earth

   The shape of the Earth is close to an ellipsoid flattened at the poles and stretched in the equatorial zone. The average radius of the Earth 6371.032 km.

   The Earth moves around the sun at an average speed of 29.765 km / s in an elliptical, near-circular orbit at an average distance from the Sun 149.6 Period of one treatment on orbit 365, 24 solar days.

Unevenness of the sun on the ecliptic:

  Apogee January 1-5, moving among the stars of 61 '/ day.
Perigee beginning of July, moving 57 '/ day.

 Earth's rotation around its axis is the average angular velocity of 7.292115 × 10-5rad / s, which roughly corresponds to the period of 23 h 56 min 4.1 sec. Rotation axis is tilted to the ecliptic plane at an angle of 66 ° 33 '39''(around 23 ° 26' inclination between the equatorial plane of the ecliptic, and adopted from 1 January 1983, when the slope decreases? Ilsya to 23 ° 26 '29 ". Effect of precession and nutation causes it to change between 21 ° 55 '24 ° 18'). This slope and an annual circulation of the Earth around the Sun cause extremely important for the Earth's climate changing seasons, and its own rotation, day and night. The Earth's rotation due to for tidal effects steadily (albeit very slowly at 0.0015 with a century) is slowed down.? meyutsya and small? s irregular variations in length of days.

   Position of geographic poles varies with a period of 434 days with an amplitude of 0.36. In addition, there are small? S seasonal move them.

Earth's surface

   The surface area of Earth's 510.2 million km2, of which approximately 70.8% is oceans. Its average depth is about 3,8 km, the maximum (the Mariana Trench in the Pacific) is 11.022 km, the water volume 1370 million km3, average salinity of 35 g / liter. Su? And is respectively 29.2% and forms? Have continents and islands. It rises above sea level on average by 875 m, the most? Th height (vertical? Ina Qomolangma in the Himalayas), 8848 m.

     The lowest point of the planet is even lower. During the period from 1930 to 1999, the Dead Sea sank with a mark of 390 meters to 414 meters below sea level. Data obtained using radar satellites observe? Them for the region from 1992 to 1999 showed that on average there exists? And goes down about 2 centimeters per year, although in some areas the figure is 6 inches. Formulating a brief substance of the changes, geologists and oceanographers say the water is drained from the Dead Sea, because of which the porous rocks are dry and subside under the weight of the upper layers.

   Mountains occupy svy? E 1 / 3 of the su? And. Deserts cover about 20% of the su? And savannas and woodlands, about 20% of the forest is about 30% ice-svy? E 10%. Svy? E 10% su? And occupied by agricultural land. A significant part of the northern territories is permafrost. For minuv? S 20 years since the beginning of the detailed space research since 1981 Northern floor? Arie on? Her world has become much greener. One possible reason for this phenomenon experts call global warming. If the ice and snow on the ground melted, the sea level rose by more than 50m, which would lead to the flooding of huge areas.

   A new analysis of data from NASA satellites by the end of 2002, indicate that the area of perennial ice in the Arctic decrease? Aetsya at a rate far exceeding its earlier estimate. Between 1978 and 2000. area of ice cover in the Arctic Ocean decreased? ilas to 1.2 million km2, roughly the area of Britain. Its rate of melting is about 9% per decade. ? Tests, wires? Party or in previous years, given the rate of melting is £ th about 3% per decade. In 2002, the ice? Apka was the smallest? She ever recorded. Reduction of surface ice in the Arctic Ocean is marked on the background of the trend towards increase? Eniyu average summer temperatures in polar regions by an average of 1.2 degrees per decade. Most? Th rate of melting observed in the Chukchi Sea and Beaufort Sea in northern Canada and Alaska.

  Recent studies using satellite-based measurements have shown that the equatorial line is an increase in the diameter of the Earth since 1998, that is, the planet becomes a little more flattened (races? Iryatsya in the area of the equator). Scientists are so puzzled by this phenomenon that can not yet give a clear answer to what's going on with? Her planet and of the consequences.

   By July 2002, NASA experts have created a unique card. This is the most accurate and detailed map of the modern world. In the three-dimensional graphics are marked by the city, rivers, mountains, deserts and seas. One touch of a button you can Sauveur? It climb Everest or visit the Sahara Desert. And the show did not immediately end point, and the entire March? Route motion. On the creation of this map NASA has worked for almost two years, processed by a computer data from topographic? Attlee - more than a trillion different marks of the earth's surface.

The internal structure of the Earth

Major role in the study of the internal structure of the Earth are seismic methods, based on a study of the spread in its bulk elastic waves (both longitudinal and transverse), arising from seismic events, with natural earthquakes and explosions. Based on these studies, the Earth conventionally divided into three areas: the crust, mantle and core (center). Outside? Tions layer crust-has an average thickness of about 35 km. The main types of continental crust (continental) and the ocean, in the transition zone from continent to ocean crust developed intermediate type. The crustal thickness varies enough? Iroki within: oceanic crust (with a layer of water) has a thickness of about 10 km, whereas the thickness of continental crust in the tens of times larger E.

Solid iron and nickel

Surface sediments occupy a layer about 2 km. Beneath them lies a granite layer (on the continents has a thickness 20 km) and lower-about 14-km (and on the continents and oceans) the basalt layer (lower crust). Average densities are: 2.6 g/cm3, the Earth's surface, 2.67 g/cm3, with granite, 2.85 g/cm3, a basalt.

At a depth of about 35 to 2885 km stretches Earth's mantle, which is also called a silicate shell. It is separated from the bark of a sharp boundary (the so-called border Mohorovicha, or "Moho"), which is deeper than the velocity of both longitudinal and transverse elastic seismic waves, as well as mechanical density abruptly increased. Density in the mantle increases with depth from about 3.3 to 9.7 g/cm3.

  Recent research conducted at Harvard on the basis of information on more than 300,000 earthquakes product? Units? Them in the years 1964-1994, showed that there is an intrinsic part of the inner core - a diameter of about 600 kilometers from the center of the Earth's temperature to 7500K.

  In the cortex, and (partly) in the mantle are about? Irnye lithospheric plates. ? X secular movement not only determine the drift of continents, notably affecting the face of the earth, but have respect? Enie and to the location of seismic zones on the planet. According to the concepts of planetary surface of the Earth is very young. Basaltic rocks forming the bottom of the ocean - one of the youngest. Precambrian shields, which cover about 10% of the surface, the oldest and closest to the surface covered with craters of the other planets. Weather processes have smoothed the surface of the earth all traces Speaking as someone who? Ihsya on it sometime crater, except for you? Then a few.
Another observed seismic methods border (border Gutenberg) between the mantle and beyond? Him nucleus located at a depth of 2775 km. Her longitudinal wave velocity decreases from 13.6 km / s (the mantle) to 8,1 km / s (the nucleus), and the speed of shear waves decreases? Aetsya from 7,3 km / s to zero. The latter means that out? Her core is liquid. According to current ideas out? Its core consists of sulfur (12%) and iron (88%). Finally, at depths svy? E 5120 km seismic methods detect the presence of the solid inner core, which accounts for 1.7% of the mass of Earth. Presumably, this iron-nickel alloy (80% Fe, 20% Ni).

Chemical composition in percentage by mass of the Earth


SiO2 31,16 CaO 2,16 Fe 23,6
Mg 25,86 Na2O 0,39 Si 4,0
Fe2O3 5,55 FeO 0,31 Ni 3,6
Al2O3 2,44 remaining 1.16

Among the many chemical elements that make up the Earth, there are radioactive. ? X decay and gravitational differentiation (movement of more dense matter in the central and less dense in the peripheral area of the world) lead to the generation of heat. The temperature in the central part of the Earth about 5000 ° C. Maximum surface temperature approaching 60 ° C (in tropical deserts of Africa and North America) and the minimum is about -90 ° C (in the central regions of Antarctica).

The pressure steadily increases with depth from 0 to 3.61 SE. Heat from the Earth's surface is transferred to her by heat conduction and convection.

Density at the center of the Earth about 12.5 g/cm3.

The Earth's atmosphere

 Earth's atmosphere? (From the Greek. Atmos - pairs and the world), air? Nye environment around the Earth, rotating with it, weight approx. 5.15 × 1015 m. The density of the atmosphere, it occupies an intermediate position between Venus and Mars. It is unique in that respect? Enii, which has about? Irnymi reserves of liquid water. Complex interaction between ocean, atmosphere and planetary surface determines its energy balance and temperature regime. Cloud cover usually covers about 50% of the surface, and the heat remaining in the atmosphere (greenhouse effect), raises the average temperature over 30 degrees.
  The composition of the Earth's surface: 78,1% nitrogen, 21% oxygen, 0.9% argon in small fractions of percent carbon dioxide, hydrogen, helium, neon and other gases. In the lower 20 km contains water vapor (the Earth's surface - from 3% in the tropics to 2.10 -5% in Antarctica), the amount of which decreases rapidly with height. Carbon dioxide - the most important trace component of air. High concentrations of oxygen (arose? Nd about 2000 million years ago) is a direct result of the existence of plants. The presence of oxygen allowed to form in the upper atmosphere ozone layer (at an altitude of 20-25 km), which shields the planet's surface from solar ultraviolet radiation harmful to life.
 You? E 100 km increases the proportion of light gases and at very large? Their altitudes dominated by helium and hydrogen, the molecules can be decomposed into atoms and ions, forming the ionosphere. Pressure and air density at the Earth's atmosphere decreases with height. Depending on the temperature distribution the Earth's atmosphere is divided into the troposphere, stratosphere, mesosphere, thermosphere, exosphere. Uneven heat it contributes to global atmospheric circulation, which affects weather and climate. The Earth's atmosphere has an electric field.

  All types of luminescence originating in the Earth's upper atmosphere (night airglow), excluding the thermal radiation, the aurora, lightning and bright streaks of meteors. Nocturnal emission spectrum ranges from 100 nm to 22.5 microns. The bulk of the emission arises in a layer thickness from 30 to 40 miles on a typical altitude of 100 km and an emission wavelength of 558 nm oxygen. ? Is space glow of the sky looks like a greenish light ring around the Earth.

 Troposphere (from the Greek. Tropos - turning and the world), the lower, basal layer of the atmosphere to an altitude of 8-10 km in the polar, 10-12 km in the middle and 16-18 km in the tropics? Irotah. In the troposphere, there are more than 1/5vsey mass of air, highly developed turbulence and convection, the predominant focus of water vapor, clouds arise, developing cyclones and anticyclones - all happening here processes play a decisive role for the formation of weather on the planet. The temperature in the troposphere decreases with increasing altitude. The troposphere is bounded above the tropopause, which corresponds to a transition to more sustainable conditions of lying are you? E stratosphere.

Stratosphere (from Lat. Stratum - the layer and sphere), the layer of atmosphere that lies above the troposphere from 8-10 km in high? Irotah and from 16-18 km near the equator to 50-55 km. The stratosphere is characterized by an increase in temperature with height ranging from -40 ° C (-80 ° C) to temperatures close to 0 ° C, low turbulence, void content of the water vapor increase? Receding compared with below-and you? Elezhaschimi layers of ozone.

Ozone (from the Greek. Ozon - scented), O3, allotropic modification of oxygen. Gas blue with a sharp odor, boiling point - 112 ° C, a strong oxidizer. When the pain? Their concentrations can be expanded with the explosion. Formed from O2 by electrical discharge (eg during a thunderstorm) and under the influence of ultraviolet radiation (in the stratosphere by ultraviolet radiation from the sun). The bulk of O3 in the atmosphere is a layer - ozone layer - at a height of 10 to 50 km with a maximum concentration at an altitude of 20-25 km. This layer protects living organisms on Earth from the harmful effects of short-wave ultraviolet radiation from the sun. Absorbs light with wavelengths from 240 to 270nm, and strongly absorbs in the range 200-320nm, while the oxygen is mainly absorbs up to 170nm. The main reason for the appearance of ozone in the Earth - lightning. In the promo? Tainty O3 receive the action of the air electric discharge. ? Use for disinfection of water and air.

  ? ONOSFERA, upper atmosphere, ranging from 50 - 85 km to 600km, characterized by a high content of atmospheric ions and free electrons. Atoms and molecules in this layer is heavily ionized by the action of solar radiation, particularly ultraviolet radiation. Moving charged particles in the magnetic field lines to the polar regions on? Irotah from 60 to 75 ° leads to the appearance of the aurora. The upper boundary of the ionosphere - beyond? The average of the Earth's magnetosphere. The reason for increase? Eniya air ionization in the ionosphere - the decomposition of molecules of gases under the action of ultraviolet and X-ray solar radiation and cosmic rays. ? Onosfera has pain? Th influence on the propagation of radio waves. Ionosphere consists of the mesosphere and thermosphere.

Polyarny? YANG? E-rapidly changing multi-colored patterns of light, observed from time to time in the night or the night sky, usually in the high? Irotnyh areas of the Earth (both the north and south). Green and red colors correspond to emission lines of oxygen and nitrogen molecules that are excited by energetic particles coming from the Sun. Auroras occur at altitudes of 100 km.
During the auroras in the ionosphere occur numerous processes such as disturbance of the geomagnetic field, ionospheric electric currents and X-rays. In the invisible parts of the spectrum emitted much pain? E energy than in the visible range. The appearance of the aurora is associated with the solar cycle, the rotation of the Sun, seasonal changes and magnetic activity.
Auroras take several basic forms. Quiet arcs or bands? Irina several tens of miles from east to west distance of 1000 km. Bands may be phased out, taking a spiral or S-shaped. You can see the rays, which go along the magnetic field. Auroral spots - a certain glow of the sky without the formation of any form. ? Zredka occur on? Irnye auroras in the form of draperies.

The mesosphere is located approximately 80-85 km, above which there are (usually at a height of approximately 85 km) noctilucent clouds. Here, temperature decreases with height? Aetsya, reaching -90 ° C at the upper limit (the mesopause).