Earth

The Blue Marble, taken from Apollo 17
Orbital characteristics (Epoch J2000)
Semi-major axis	149,597,887 km (1.000 000 11 AU)
Orbital circumference	0.940 Tm (6.283 AU)
Orbital eccentricity	0.016 710 22
Perihelion	147,098,074 km (0.983 289 9 AU)
Aphelion	152,097,701 km (1.016 710 3 AU)
Sidereal orbit period	365.256 96 d (1.000 019 1 a)
Synodic period	n/a
Average orbital speed	29.783 km/s
Max. orbital speed	30.287 km/s
Min. orbital speed	29.291 km/s
Orbital inclination to ecliptic	0.000 05° (7.25° to Sun's equator)
Longitude of the ascending node	348.739 36°
Argument of the perihelion	114.207 83°
Satellites	1 (the Moon) (see also 3753 Cruithne)
Physical characteristics
Equatorial diameter	12,756.28 km
Polar diameter	12,713.56 km
Mean diameter	12,742.02 km
Oblateness	0.003 35
Equatorial circumference	40,075 km
Polar circumference	40,008 km
Surface area	510,067,420 km²
- land	148,847,000 km² (29.2 %)
- water	361,220,420 km² (70.8 %)
Volume	1.0832×1012 km³
Mass	5.9736×1024 kg
Density	5,515 kg/m³
Equatorial surface gravity	9.780 m/s² (0.997 32 g)
Escape velocity	11.186 km/s
Sidereal rotation period	0.997 258 d (23.934 h)
Rotational velocity (at the equator)	465.11 m/s
Axial tilt	23.439 281°
Right ascension of North pole	0° (0 h 0 min 0 s)
Declination	90°
Albedo	0.367
Surface temperature - min - mean - max	185 K 287 K 331 K
Surface pressure	100 kPa
Atmospheric constituents
nitrogen	77 %
oxygen	21 %
argon	1 %
carbon dioxide	trace
water vapor	trace
edit (http://en.wikipedia.org/w/index.php?title=Template:Planet_Infobox/Earth&action=edit)

Earth, also known as the Earth or Terra, is the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. The planet formed around 4.57 billion (4.57×10⁹) years ago and shortly thereafter acquired its single natural satellite, the Moon. Its dominant sentient species is the human (Homo sapiens sapiens). Download high resolution version (2320x2407, 2389 KB) A version of The Blue Marble. ... The Blue Marble is a famous photograph of Earth taken on 7 December 1972 by the crew of the Apollo 17 spacecraft at a distance of about 45,000 km. ... Apollo 17 was the eleventh manned space mission in the NASA Apollo program, and was the sixth and last mission to date to land on the Moon. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... The J2000. ... In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... A kilometre (American spelling: kilometer) (symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... The astronomical unit (AU or au or a. ... The circumference is the distance around a closed curve. ... A terametre (American spelling: terameter) (symbol: Tm) is a unit of length equal to 1012 metres. ... (This page refers to eccitricity in astrodynamics. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ... A day is any of several different units of time. ... A Julian year is the length of an average year in the Julian calendar, 365. ... The orbital period is the time it takes a planet (or another object) to make one full orbit. ... The orbital speed of a body, generally a planet, a natural satellite, an artificial satellite, or a multiple star, is the speed at which it orbits around the barycenter of a system, usually around a more massive body. ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ... Inclination is one of the six orbital parameters describing the shape and orientation of a celestial orbit and is the angular distance of the orbital plane from the plane of the reference (usually planets equator or the ecliptic), stated in degrees. ... This article describes degree as a unit of angle. ... A Sun is the star at the centre of a solar system. ... The Longitude of the ascending node () is one of the orbital elements used to specify the orbit of an object in space. ... The argument of the perihelion is one of the orbital elements describing the orbit of a planet. ... The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... 3753 Cruithne is an asteroid in orbit around the Sun. ... In geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. ... For the geometric term, see diameter. ... For other uses of the word pole, see Pole (disambiguation). ... Note: Earth radius is sometimes used as a unit of distance, especially in astronomy and geology. ... Oblate also refers to a member of the Roman Catholic religious order of the Missionary Oblates of Mary Immaculate, or in some cases to a lay or religious person who has officially associated himself (or herself) with a monastic community such as the Benedictines for reasons of personal enrichment without... The circumference is the distance around a closed curve. ... This article explains the meaning of area as a physical quantity. ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... Volume (also called capacity) is a quantification of how much space an object occupies. ... A cubic kilometre (symbol km³) is an SI derived unit of volume. ... Mass is a property of physical objects that, roughly speaking, measures the amount of matter they contain. ... The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... Density (symbol: ρ - Greek: rho) is a measure of mass per unit of volume. ... Kilogram per cubic metre is the SI measure of density and is represented as kg/m³, where kg stands for kilogram and m³ stands for cubic metre. ... This article covers the physics of gravitation. ... Metres per second squared is the SI derived unit of acceleration (scalar) and (vector), defined by distance in metres divided by time in seconds and again divided by time in seconds. ... g (also gee, g-force or g-load) is a non-SI unit of acceleration defined as exactly 9. ... Escape Velocity means two things: the term escape velocity in physics the computer game Escape Velocity This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... A day is any of several different units of time. ... The hour was originally defined in Egypt as 1/24 of a day, based on their duo-decimal numbering system (which counted finger joints on each hand). ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... This article describes degree as a unit of angle. ... Right ascension (RA; symbol α: Greek letter alpha) is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. ... In astronomy declination (dec) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. ... This article discusses the physical or planetological property of albedo. ... Temperature is the physical property of a system which underlies the common notions of hot and cold; the material with the higher temperature is said to be hotter. ... The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... Atmospheric pressure is the pressure caused by the weight of air above any area in the Earths atmosphere. ... The pascal (symbol Pa) is the SI unit of pressure. ... General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ... General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18 (VIIIA), 3, p Density, Hardness 1. ... Carbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. ... A falling water droplet Water (from the Anglo-Saxon and Low German wæter) is a colourless, tasteless, and odourless substance that is essential to all known forms of life and is the most universal solvent. ... A Sun is the star at the centre of a solar system. ... Mosaic of the planets of the solar system, excluding Pluto, and including Earths Moon. ... A terrestrial planet or telluric planet is a planet which is primarily composed of silicate rocks. ... For the scientific journal named Science, see Science (journal). ... This article concerns the primary meanings of life in biology. ... The age of the Earth is estimated to be 4. ... The word billion, and its equivalents in other languages, refer to one of two different numbers. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... Sentience is the capacity for basic consciousness -- the ability to feel or perceive, not necessarily including the faculty of self-awareness. ... Binomial name Homo sapiens Linnaeus, 1758 Subspecies Homo sapiens idaltu (extinct) Homo sapiens sapiens Human beings define themselves in biological, social, and spiritual terms. ...

Its symbol consists of a circled cross, representing a meridian and the equator; a variant puts the cross atop the circle (Unicode: ⊕ or ♁). Meridian is: Meridian (astronomy): an imaginary circle perpendicular to the horizon. ... In geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. ... In computing, Unicode is the international standard whose goal is to provide the means to encode the text of every document people want to store in computers. ...

Physical characteristics

Shape

The Earth is approximately a slightly oblate spheroid, with an average diameter of approximately 12,742 km. The maximum deviations from this are the highest point on Earth (the summit of Mount Everest, which is only 8,850 m) and the lowest (the bottom of the Mariana Trench, at 10,911 m below sea level). Thus the Earth is an oblate spheroid within a tolerance of one part in about 584, or 0.17 %. The mass of the Earth is approximately 6,000 yottagrams (6 x 10²⁴ kg). Oblate also refers to a member of the Roman Catholic religious order of the Missionary Oblates of Mary Immaculate, or in some cases to a lay or religious person who has officially associated himself (or herself) with a monastic community such as the Benedictines for reasons of personal enrichment without... A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. ... This article is about the Alpine mountain. ... Mariana Trench on Pacific Ocean map The Mariana Trench (or Marianas Trench) is the deepest known submarine trench, and the deepest location in the Earths crust itself. ... Tolerance in engineering is an allowance made for imperfections in a manufactured object. ...

Structure

The interior of Earth, like that of the other terrestrial planets, is chemically divided into an outer siliceous solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core. The liquid outer core gives rise to a weak magnetic field due to the convection of its electrically conductive material. A terrestrial planet or telluric planet is a planet which is primarily composed of silicate rocks. ... General Name, Symbol, Number silicon, Si, 14 Series metalloid Group, Period, Block 14 (IVA), 3, p Density, Hardness 2330 kg/m3, 6. ... Earth cutaway from core to exosphere. ... The mantle is the layer in the structure of the Earth that lies directly under the Earths crust. ... A magnetosphere is the region around an astronomical object, in which phenomena are dominated by its magnetic field. ...

New material constantly finds its way to the surface through volcanoes and cracks in the ocean floors (see seafloor spreading). Much of Earth's crust is less than 100 million (1×10⁸) years old; the very oldest parts of the crust are as much as 4.4 billion (4.4×10⁹) years old [1] (http://spaceflightnow.com/news/n0101/14earthwater/). Seafloor spreading is a part of the theory of plate tectonics. ...

Taken as a whole, the Earth's composition by mass [2] (http://earthref.org/cgi-bin/er.cgi?s=erda.cgi?n=547) is:

oxygen:	28	.2	%
iron:	34	.1	%
silicon:	17	.2	%
magnesium:	15	.9	%
nickel:	1	.6	%
calcium:	1	.6	%
aluminium:	1	.5	%
sulfur:	0	.70	%
sodium:	0	.25	%
titanium:	0	.071	%
potassium:	0	.019	%
other elements:	0	.53	%

General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metal Group, Period, Block 8 (VIIIB), 4, d Density, Hardness 7874 kg/m3, 4. ... General Name, Symbol, Number silicon, Si, 14 Series metalloid Group, Period, Block 14 (IVA), 3, p Density, Hardness 2330 kg/m3, 6. ... General Name, Symbol, Number magnesium, Mg, 12 Series alkaline earth metals Group, Period, Block 2 (IIA), 3, s Density, Hardness 1738 kg/m³, 2. ... This article is about the element nickel. ... General Name, Symbol, Number calcium, Ca, 20 Series alkaline earth metal Group, Period, Block 2 (IIA), 4, s Density, Hardness 1550 kg/m3, 1. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16 (VIA), 3, p Density, Hardness 1960 kg/m3, 2 Appearance Lemon yellow at STP Atomic properties Atomic weight 32. ... General Name, Symbol, Number sodium, Na, 11 Series alkali metal Group, Period, Block 1 (IA), 3 , s Density, Hardness 968 kg/m3, 0. ... General Name, Symbol, Number Titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Density, Hardness 4507 kg/m3, 6 Appearance Silvery metallic Atomic properties Atomic weight 47. ... General Name, Symbol, Number potassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4, s Density, Hardness 856 kg/m3, 0. ...

Interior

Interior heat

The interior of Earth reaches temperatures of 5270 kelvins. The planet's internal heat was originally generated during its accretion (see gravitational binding energy), and since then additional heat has continued to be generated by the decay of radioactive elements such as uranium, thorium, and potassium. The heat flow from the interior to the surface is only 1/20,000 as great as the energy received from the Sun. The kelvin (symbol: K) is the SI unit of temperature, and is one of the seven SI base units. ... The gravitational binding energy of an object is the amount of energy required to accelerate every component of that object to the escape velocity of every other component. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ... General Name, Symbol, Number Uranium, U, 92 Chemical series Actinides Period, Block 7, f Density, Hardness 19050 kg/m3, 6 Appearance silvery-white metal Atomic properties Atomic weight 238. ... General Name, Symbol, Number thorium, Th, 90 Chemical series Transition metals Period, Block 7 , f Density, Hardness 11724 kg/m3, 3. ... General Name, Symbol, Number potassium, K, 19 Series alkali metals Group, Period, Block 1(IA), 4, s Density, Hardness 856 kg/m3, 0. ...

Structure

Earth's composition (by depth below surface):

• 0 to 60 km - Lithosphere (locally varies 5-200 km)
  • 0 to 35 km - Crust (locally varies 5-70 km)
• 35 to 2890 km - Mantle
  • 100 to 700 km - Asthenosphere
• 2890 to 5100 km - Outer Core
• 5100 to 6378 km - Inner Core

The lithosphere (from the Greek for rocky sphere) is the solid outermost shell of a rocky planet. ... The asthenosphere (from the Greek asthenia, weakness) is the region of the Earth between 100-200 km below the surface, but may extend as deep as 400 km. ...

The core

The average density of Earth is 5515 kg/m³, making it the densest planet in the Solar system. Since the average density of surface material is only around 3000 kg/m³, we must conclude that denser materials exist within the core of the Earth. In its earliest stages, about 4.5 billion (4.5×10⁹) years ago, melting would have caused denser substances to sink towards the center in a process called planetary differentiation, while less dense materials would have migrated to the crust. As a result, the core is largely composed of iron (80%), along with nickel and silicon; while other dense elements, such as lead and uranium, are either too rare to be significant or tend to bind to lighter elements and thus remain in the crust (see: felsic materials). The international prototype, made of platinum-iridium, which is kept at the BIPM under conditions specified by the 1st CGPM in 1889. ... metre or meter, see meter (disambiguation) The metre is the basic unit of length in the International System of Units. ... In cosmogony, planetary differentiation is a process by which the denser portions of a planet will sink to the center; while less dense materials rise to the surface. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica, oxygen, aluminium, sodium, and potassium. ...

The core is divided into two parts, a solid inner core with a radius of ~1250 km and a liquid outer core extending beyond it to a radius of ~3500 km. The inner core is generally believed to be solid and composed primarily of iron and some nickel. Some have argued that the inner core may be in the form of a single iron crystal. The outer core surrounds the inner core and is believed to be composed of liquid iron mixed with liquid nickel and trace amounts of lighter elements. It is generally believed that convection in the outer core, combined with stirring caused by the Earth's rotation (see: Coriolis forces), gives rise to the Earth's magnetic field through a process known as the dynamo theory. The solid inner core is too hot to hold a permanent magnetic field (see: Curie temperature) but probably acts to stabilise the magnetic field generated by the liquid outer core. The word radius (Latin for wheel spoke; plural radii, pronounced ray-dee-eye) has several meanings in English: In classical geometry, a radius of a circle or sphere is any line segment with one endpoint on the circle (i. ... Quartz crystal A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... In physics, the Coriolis effect is an inertial force first described by Gaspard-Gustave Coriolis, a French scientist, in 1835. ... Earths magnetic field (the surface magnetic field) is approximately a magnetic dipole, with one pole near the geographic north pole and the other near the geographic south pole. ... Dynamo theory proposes a mechanism by which a celestial body such as the earth generates a magnetic field. ... In physics, the Curie point, or Curie temperature, is the temperature above which a ferromagnet loses its ferromagnetic ability to possess a net (spontaneous) magnetization in the absence of an external magnetic field. ...

Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet, by ~2° per year (Comins DEU-p.82). A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ...

Earth cutaway from core to exosphere. Partially to scale.

Earth and atmosphere cutaway illustration. ... Earth and atmosphere cutaway illustration. ...

Mantle

Earth's mantle extends to a depth of 2890 km. The pressure, at the bottom of the mantle, is ~140 GPa (1.4 Matm). It is largely composed of substances rich in iron and magnesium. The melting point of a substance depends on the pressure it is under. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of this region is thought solid while the upper mantle is plastic (semi-molten). The viscosity of the upper mantle ranges between 10²¹ and 10²⁴ Pa·s, depending on depth [3] (http://www2.uni-jena.de/chemie/geowiss/geodyn/poster2.html). Thus, the upper mantle can only flow very slowly. Earth cutaway from core to exosphere. ... Pressure (symbol: p or P) is the measure of the force that acts on a unit area. ... The pascal (symbol Pa) is the SI unit of pressure. ... Atmospheric pressure is the pressure caused by the weight of air above any area in the Earths atmosphere. ... The term plastics covers a range of synthetic or semi-synthetic polymerization products. ... The pascal second (symbol Pa·s) is the SI unit of dynamic viscosity. ...

Why is the inner core thought solid, the outer core thought liquid, and the mantle solid/plastic? The melting points of iron rich substances are higher than pure iron. The core is composed almost entirely of pure iron, while iron rich substances are more common outside the core. So, surface iron-substances are solid, upper mantle iron-substances are semi-molten (as it is hot and they are under relatively little pressure), lower mantle iron-substances are solid (as they are under tremendous pressure), outer core pure iron is liquid as it has a very low melting point (despite enormous pressure), and the inner core is solid due to the overwhelming pressure found at the center of the planet.

Crust

The crust ranges from 5 to 70 km in depth. The thin parts are oceanic crust composed of dense (mafic) iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks. The crust-mantle boundary occurs as two physically different events. Firstly, there is a discontinuity in the seismic velocity which is known as the Mohorovičić discontinuity or Moho. The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain no feldspars (below). The second event is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites which has been observed from deep parts of the oceanic crust that have been obducted into the continental crust and preseved as ophiolite sequences. Oceanic crust is the part of Earths lithosphere which underlies the ocean basins. ... In geology, mafic minerals are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... Sedimentary, volcanic, plutonic, metamorphic rock types of North America. ... The Continental Crust is the layer of granitic and sedimentary rock which forms the continents and the areas of shallow seabed close to their shores, known as continental shelves. ... Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements, such as silica, oxygen, aluminium, sodium, and potassium. ... General Name, Symbol, Number sodium, Na, 11 Series alkali metal Group, Period, Block 1 (IA), 3 , s Density, Hardness 968 kg/m3, 0. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ... A seismic wave is a wave that travels through the Earth, often as the result of an earthquake or explosion. ... The Mohorovicic discontinuity, usually referred to as the Moho, is the boundary between the Earths crust and the mantle. ... Feldspar (from the German Feld, field, and Spat, a rock that does not contain ore) is the name of an important group of rock-forming minerals which make up perhaps as much as 60% of the Earths crust. ... -1... Ultramafic rocks are igneous rocks with very low silica content (less than 45%) and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). ... Peridotite Peridotite is a dense, coarse grained ultrabasic rock, consisting mainly of the minerals olivine and pyroxene. ... Obduction is the overthrusting of continental crust by oceanic crust or mantle rocks. ... Ophiolites are sections of the oceanic crust and the subjacent upper mantle that have been uplifted or emplaced to be exposed within continental crustal rocks. ...

Biosphere

Earth is the only place where life is known to exist. The planet's lifeforms are sometimes said to form a "biosphere". This biosphere is generally believed to have begun evolving about 3.5 billion (3.5×10⁹) years ago. The biosphere is divided into a number of biomes, inhabited by broadly similar flora and fauna. On land, biomes are separated primarily by latitude. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the Equator. The biosphere is that part of a planet earths outer shell—including air, land, and water—within which life occurs, and which biotic processes in turn alter or transform. ... Charles Darwin, the father of evolutionary theory Although generally, evolution is taken to mean any process of change over time, in the context of life science, evolution is a change in the traits of living organisms over generations, including the emergence of new species. ... In ecology, a biome is a major regional group of distinctive plant and animal communities well adapted to the regions physical environment. ... Flora is a collective term for plant life. ... Fauna is a collective term for animal life. ... Latitude, denoted φ, gives the location of a place on Earth north or south of the Equator. ... Arctic Circle - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Zoomable PDF of the map this is based on The Antarctic Circle is one of the five major circles of latitude that mark maps of the Earth. ... Divisions Green algae land plants (embryophytes) non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses vascular plants (tracheophytes) seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongue ferns seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria Acoelomorpha Orthonectida Rhombozoa ?Myxozoa Superphylum Deuterostomia    Chordata (vertebrates, etc. ... In geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. ...

Atmosphere

Earth has a relatively thick atmosphere composed of 78% nitrogen, 21% oxygen, and 1% argon, plus traces of other gases including carbon dioxide and water vapor. The atmosphere acts as a buffer between Earth and the Sun. The Earth's atmospheric composition is unstable and is maintained by the biosphere. Namely, the large amount of free diatomic oxygen is maintained through solar energy by the Earth's plants, and without the plants supplying it, the oxygen in the atmosphere will over geological timescales combine with material from the surface of the Earth. Free oxygen in the atmosphere is a signature of life. Earths atmosphere is the layer of gases surrounding the planet Earth and retained by the Earths gravity. ... General Name, Symbol, Number Nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15 (VA), 2 , p Density 1. ... General Name, Symbol, Number Oxygen, O, 8 Chemical series nonmetals Group, Period, Block 16 (VIA), 2, p Density, Hardness 1. ... General Name, Symbol, Number argon, Ar, 18 Chemical series noble gases Group, Period, Block 18 (VIIIA), 3, p Density, Hardness 1. ... Carbon dioxide is an atmospheric gas composed of one carbon and two oxygen atoms. ... This article describes water from a scientific and technical perspective. ... Divisions Green algae land plants (embryophytes) non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses vascular plants (tracheophytes) seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongue ferns seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering...

The layers, troposphere, stratosphere, mesosphere, thermosphere, and the exosphere, vary around the globe and in response to seasonal changes. The troposphere is the lowermost portion of Earths atmosphere and the one in which most weather phenomena occur. ... The Stratosphere is also a major hotel and casino resort in Las Vegas. ... The mesosphere (from the Greek words mesos = middle and sfaira = ball) is the layer of the Earths atmosphere that is directly above the stratosphere and directly below the thermosphere. ... The thermosphere is the layer of the Earths atmosphere directly above the mesosphere and directly below the exosphere. ... The exosphere (from the Greek words exo = out(side) and sphaira = ball) is the uppermost layer of the atmosphere. ...

The total mass of the atmosphere is about 5.1 × 10¹⁸ kg, ca. 0.9 ppm of the Earth's total mass. Parts per million (ppm) is a measure of concentration that is used where low levels of concentration are significant. ...

Hydrosphere

A Plate Carrée Projection of a composite satellite image of Earth

Earth is the only planet in our solar system whose surface has liquid water. Water covers 71% of Earth's surface (97% of it being sea water and 3% fresh water [4] (http://earthobservatory.nasa.gov/Library/Water/)) and divides it into five oceans and seven continents. Earth's solar orbit, vulcanism, gravity, greenhouse effect, magnetic field and oxygen-rich atmosphere seem to combine to make Earth a water planet. Download high resolution version (1024x512, 129 KB)Subject: Satellite composite image of the World, in Plate Carrée Projection Source: [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Download high resolution version (1024x512, 129 KB)Subject: Satellite composite image of the World, in Plate Carrée Projection Source: [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Equidistant cylindrical projection of the Globe Equidistant cylindrical projection of a composite satellite image (NASA) The Plate Carrée or Equidistant Cylindrical Projection or Geographic Projection, is a very simple map projection that has been in use since the earliest days of spherical cartography. ... Mosaic of the planets of the solar system, excluding Pluto, and including Earths Moon. ... This article describes water from a scientific and technical perspective. ... Dymaxion map by Buckminster Fuller shows land mass with minimal distortion as only one continuous continent A continent (Latin continere, to hold together) is a large continuous mass of land on the planet Earth. ... In physics, an orbit is the path that an object makes, around another object, whilst under the influence of a source of centripetal force, such as gravity. ... This article is about volcanoes in geology. ... This article covers the physics of gravitation. ... The greenhouse effect first discovered by Jean Baptiste Joseph Fourier in 1824 is the process by which an atmosphere warms a planet. ... In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving charges. ...

Earth is actually beyond the outer edge of the orbits which would be warm enough to form liquid water. Without some form of a greenhouse effect, Earth's water would freeze. Paleontological evidence indicates that at one point after blue-green bacteria (Cyanobacteria) had colonized the oceans, the greenhouse effect failed, and Earth's oceans may have completely frozen over for 10 to 100 million years in what is called a snowball Earth event. The greenhouse effect first discovered by Jean Baptiste Joseph Fourier in 1824 is the process by which an atmosphere warms a planet. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... Cyanobacteria (Greek: cyanos = blue) are a phylum of aquatic bacteria that obtain their energy through photosynthesis. ... The Snowball Earth, also known as the Varangian glaciation, is an hypothesis that has been around for several decades but which has recently been reformulated by Paul F. Hoffman, Sturgis Hooper Professor of Geology at Harvard University. ...

On other planets, such as Venus, gaseous water is destroyed (cracked) by solar ultraviolet radiation, and the hydrogen is ionized and blown away by the solar wind. This effect is slow, but inexorable. This is one hypothesis explaining why Venus has no water. Without hydrogen, the oxygen interacts with the surface and is bound up in solid minerals. (*min temperature refers to cloud tops only) Atmospheric characteristics Atmospheric pressure 9. ... Ultraviolet (UV) radiation is electromagnetic radiation of a wavelength shorter than that of the visible region, but longer than that of soft X-rays. ... General Name, Symbol, Number Hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1 (IA), 1 , s Density, Hardness 0. ... ion (disambiguation) An ion is an atom or group of atoms with a net electric charge. ... A solar wind is a stream of particles (mostly high-energy protons ~ 500 keV) which are ejected from the upper atmosphere of a star (in the case of a star other than the Earths Sun, it may be called a stellar wind instead). ... Minerals are natural compounds formed through geological processes. ...

In the Earth's atmosphere, a tenuous layer of ozone within the stratosphere absorbs most of this energetic ultraviolet radiation high in the atmosphere, reducing the cracking effect. The ozone, too, can only be produced in an atmosphere with a large amount of free diatomic oxygen, and so also is dependent on the biosphere (plants). The magnetosphere also shields the ionosphere from direct scouring by the solar wind. Ozone (O3) is an allotrope of oxygen, the molecule consisting of three oxygen atoms instead of the more stable diatomic O2. ... Divisions Green algae land plants (embryophytes) non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses vascular plants (tracheophytes) seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongue ferns seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering... A magnetosphere is the region around an astronomical object, in which phenomena are dominated by its magnetic field. ... The ionosphere is the part of the atmosphere that is ionized by solar radiation. ...

Finally, vulcanism continuously emits water vapor from the interior. Earth's plate tectonics recycle carbon and water as limestone rocks are subducted into the mantle and volcanically released as gaseous carbon dioxide and steam. It is estimated that the minerals in the mantle may contain as much as 10 times the water as in all of the current oceans, though most of this trapped water will never be released. This article is about volcanoes in geology. ... Vapor (US English) or vapour (British English) is the gaseous state of matter. ... The tectonic plates of the world were mapped in the second half of the 20th century. ... General Name, Symbol, Number Carbon, C, 6 Chemical series Nonmetals Group, Period, Block 14 (IVA), 2, p Density, Hardness 2267 kg/m3 0. ... Media:Example. ... Categories: Geology stubs | Plate tectonics ...

The total mass of the hydrosphere is about 1.4 × 10²¹ kg, ca. 0.023 % of the Earth's total mass.

Earth in the Solar System

It takes Earth 23 hours, 56 minutes and 4.09 seconds (1 sidereal day) to rotate around the axis connecting the north pole and the south pole. Thus from Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e. a Sun or Moon diameter every two minutes. On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... A North Pole is the northernmost point on any planet. ... Location of the South Pole in the Antarctic continent. ... A meteor is the visible path of a meteoroid that enters the Earths (or another bodys) atmosphere, commonly called a shooting star or falling star. ...

Earth orbits the Sun every 365.2564 mean solar days (1 sidereal year). Thus from Earth this gives an apparent movement of the Sun with respect to the stars at a rate of ca. 1 °/day, i.e. a Sun or Moon diameter every 12 hours eastward. The sidereal year is the time for the Sun to return to the same position in respect to the stars of the celestial sphere. ...

The orbital speed of the Earth averages about 30 km/s, which is enough to cover one Earth diameter (~12,700 km) in 7 minutes, and one distance to the Moon (384,000 km) in 4 hours.

Earth has one natural satellite, the Moon, which orbits around Earth every 27 1/3 days. Thus from Earth this gives an apparent movement of the Moon with respect to the Sun and the stars at a rate of roughly 12 °/day, i.e. a Moon diameter every hour eastward. The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... In Egyptian mythology, Month is an alternate spelling for Menthu. ...

Viewed from Earth's north pole, the motion of Earth, its moon and their axial rotations are all counterclockwise. A clockwise motion is one that proceeds like the clocks hands: from the top to the right, then down and then to the left, and back to the top. ...

The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.5 degrees against the Earth-Sun plane (which causes the seasons), and the Earth-Moon plane is tilted about 5 degrees against the Earth-Sun plane (otherwise there would be an eclipse every month). Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... This article is about divisions of a year. ...

The Hill sphere (sphere of influence) of the Earth is about 1.5 Gm (930 thousand miles) in radius, within which one natural satellite (the Moon) comfortably orbits. A Hill sphere approximates the gravitational sphere of influence of one astronomical body in the face of perturbations from another heavier body around which it orbits. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ...

In an inertial reference frame, the Earth's axis undergoes a slow precessional motion with a period of some 25,800 years, as well as a nutation with a main period of 18.6 years. These motions are caused by the differential attraction of Sun and Moon on the equatorial bulge due to the Earth's oblateness. In a reference frame attached to the solid body of the Earth, its rotation is also slightly irregular due to polar motion. The polar motion is quasi-periodic, containing an annual component and a component with a 14 month period called the Chandler wobble. Also the rotational velocity varies, a phenomenon known as length of day variation. Precession (also called gyroscopic precession) is the phenomenon by which the axis of a spinning object (e. ... Rotation (green), Precession (blue) and Nutation (red) of the Earth Nutation is a slight irregular motion (etymologically a nodding) in the axis of rotation of a planet, due to the fact that the tidal forces which cause precession of the equinoxes vary over time so that the speed of precession... The Earths rotation axis tends, like the axis of a gyroscope, to maintain its orientation in inertial space. ... The Chandler wobble is a small variation in Earths axis of rotation, discovered by American astronomer Seth Carlo Chandler in 1891. ... A day is any of several different units of time. ...

The Moon

Luna, or simply 'the Moon', is a relatively large terrestrial planet-like satellite, about one quarter of Earth's diameter. The natural satellites orbiting other planets are called "moons", after Earth's Moon. In geometry, the semi-major axis (also semimajor axis) a applies to ellipses and hyperbolas. ... Crust composition Oxygen 43% Silicon 21% Aluminium 10% Calcium 9% Iron 9% Magnesium 5% Titanium 2% Nickel 0. ... The common noun moon (not capitalized) is used to mean any natural satellite of the other planets. ...

The gravitational attraction between the Earth and Moon cause the tides on Earth. The same effect on the Moon has led to its tidal locking: its rotation period is the same as the time it takes to orbit the Earth. As a result it always presents the same face to the planet. This article is about tides in the ocean. ... A separate article treats the phenomenon of tidal resonance in oceanography. ...

As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases: the dark part of the face is separated from the light part by the solar terminator. In astronomy, a phase of the Moon is any of the aspects or appearances presented by the Moon as seen from Earth, determined by the portion of the Moon that is visibly illuminated by the Sun. ... A composite image showing the terminator crossing Europe and Africa The terminator is the line between the illuminated, day side and dark, night side of a planetary body (also known as the grey line). It is defined as the locus of points on a moon or planet where the line...

The Moon may enable life by moderating the weather. Paleontological evidence and computer simulations show that Earth's axial tilt is stabilised by tidal interactions with the Moon. Without this stabilization against the torques applied by the Sun and planets to the Earth's equatorial bulge, some theorists believe that the rotational axis might be chaotically unstable, as it appears to be with Mars. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result as this would make seaonal differences extreme. One pole would be pointed directly toward the Sun during summer and directly away during winter. Planetary scientists who have studied the effect claim that this might kill all large animal and higher plant life. This remains a controversial subject, however, and further studies of Mars —which shares Earth's rotation period and axial tilt, but not its large moon or liquid core— may provide additional information. Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ... This article is about the physical concept. ... Mars is the fourth planet from the Sun in the solar system, named after the Roman god of war (the counterpart of the Greek Ares), on account of its blood red color as viewed in the night sky. ... The plane of the Ecliptic is well seen in this picture from the 1994 lunar prospecting Clementine spacecraft. ... Composite satellite image showing the progress of a hurricane weather system approaching the east coast of America Weather comprises all the various phenomena that occur in the atmosphere of a planet. ... Planetary science, also known as planetology or planetary astronomy, is the science of planets and the solar system, and incorporates an interdisciplinary approach drawing from diverse sciences. ... On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ... Axial tilt is an astronomical term regarding the inclination angle of a planets rotational axis in relation to its orbital plane. ...

The Moon is just far enough away to have, when seen from Earth, very nearly the same apparent angular size as the Sun (the Sun is 400 times larger, but the Moon is 400 times closer). This allows total eclipses as well as annular eclipses to occur on Earth. Here is a diagram showing the relative sizes of the Earth and the Moon and the distance between the two (click to enlarge): Total solar eclipse in Zambia, 2001 An eclipse (Greek verb: ecleipo = cease to exist) is an astronomical event that occurs when one celestial object moves into the shadow of another. ...

Earth and Moon to scale (click to enlarge)

The Moon's origin is unknown, but one popular hypothesis states that it was formed from the collision of a Mars-sized protoplanet with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements. See Giant impact theory. Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... Download high resolution version (1024x92, 2 KB)Subject: Illustration of the Earth and the Moon at maximum distance from each other as seen from the Sun. ... In cosmogony, a protoplanet is a quasi-planetoid which is slightly larger than a planetesimal and orbits within a solar nebulas protoplanetary discs. ... Big Splash illustration The Big Splash The giant impact theory (or Big Splash or Big Whack; cf. ...

Earth also has at least one known co-orbital asteroid, 3753 Cruithne. An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... 3753 Cruithne is an asteroid in orbit around the Sun. ...

Geography

Physical map of the Earth ( Medium) ( Large 2 MB)

Map references: Subject: Physical map of the World, April, 2004 Projection: Robinson projection, Standard parallels, 38°N, 38°S Source: CIA World Factbook [1] There is a higher resolution version at Image:World-map-2004-cia-factbook-large-2m. ... Subject: Physical map of the World, April, 2004 Projection: Robinson projection, Standard parallels, 38°N, 38°S Source: CIA World Factbook [1] There is a higher resolution version at Image:World-map-2004-cia-factbook-large-2m. ... Subject: Physical map of the World, April, 2004 Projection: Robinson projection, Standard parallels, 38°N, 38°S Source: CIA World Factbook [1] There is a higher resolution version at Image:World-map-2004-cia-factbook-large-2m. ... Download high resolution version (4000x2949, 1546 KB)Physical World Map 2004-04-01 CIA World Factbook; Robinson Projection; standard parallels 38°N and 38°S File links The following pages link to this file: Wikipedia:WikiProject Maps/World World map Categories: CIA World Factbook images ...

Time Zones, Coordinates. Time zones are areas of the Earth that have adopted the same standard time, usually referred to as the local time. ... See Cartesian coordinate system or Coordinates (elementary mathematics) for a more elementary introduction to this topic. ...

Biggest geographic subdivision

Continents, Oceans Dymaxion map by Buckminster Fuller shows land mass with minimal distortion as only one continuous continent A continent (Latin continere, to hold together) is a large continuous mass of land on the planet Earth. ... Ocean (Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ...

Area:

• total: 510.073 million km²
• land: 148.94 million km²
• water: 361.132 million km²
• note: 70.8 % of the world's surface is covered by water, 29.2 % is exposed land

Land boundaries: the land boundaries in the world total 251,480 km (not counting shared boundaries twice) (Redirected from 1 E14 m2) To help compare sizes of different areas, here is a list of areas between 100 million km² and 1,000 million (American billion) km². See also areas of other orders of magnitude. ... Square kilometre (US spelling: Square kilometer), symbol km², is an SI unit of surface area. ... Land is sometimes used synonymously with country. ... A falling water droplet Water (from the Anglo-Saxon and Low German wæter) is a colourless, tasteless, and odourless substance that is essential to all known forms of life and is the most universal solvent. ...

Coastline: 356,000 km

Maritime claims: see United Nations Convention on the Law of the Sea The term United Nations Convention on Law of the Sea (UNCLOS, also called simply the Law of the Sea or LOS) refers to several United Nations events and one international treaty. ...

• contiguous zone: 24 nautical miles (44.4 km) claimed by most, but can vary
• continental shelf: 200 m depth claimed by most or to depth of exploitation; others claim 200 nautical miles (370.4 km) or to the edge of the continental margin
• exclusive fishing zone: 200 nautical miles (370.4 km) claimed by most, but can vary
• exclusive economic zone: 200 nautical miles (370.4 km) claimed by most, but can vary
• territorial sea: 12 nautical miles (22.2 km) claimed by most, but can vary
• Note: boundary situations with neighboring states prevent many countries from extending their fishing or economic zones to a full 200 nautical miles (370.4 km)
• 43 nations and other areas are completely landlocked (see list there at landlocked countries)

A nautical mile is a unit of distance, or, as physical scientists like to call it, length. ... The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the one we live in by relatively shallow seas and gulfs. ... A landlocked country is one that has no coastline. ...

Climate

Two large areas of polar climates separated by two rather narrow temperate zones from a wide equatorial band of tropical to subtropical climates. Precipitation patterns vary widely, ranging from several metres of water per year to less than a millimetre. In geography, temperate latitudes of the globe lie between the tropics and the polar circles. ... In geography, the equator is an imaginary line drawn around a planet, halfway between the poles, where the surface of the roughly spherical planet is parallel to the axis of rotation. ... The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere. ... Subtropical (or semitropical) areas are those adjacent to the tropics, usually roughly defined as the ranges 23. ...

Terrain

Elevation extremes: (measured relative to sea level) For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ...

• Lowest point on land: Dead Sea −417 m
• Lowest point overall: Mariana Trench in the Pacific Ocean −10,924 m [5] (http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html)
• Highest point: Mount Everest 8,850 m (1999 est.)

The Jordan River flowing into the Dead Sea The Dead Sea (Arabic البحر الميت,Hebrew ים המלח) is the lowest point on the Earths surface. ... To help compare different orders of magnitude this page lists lengths between 100 m and 1 km. ... Mariana Trench on Pacific Ocean map The Mariana Trench (or Marianas Trench) is the deepest known submarine trench, and the deepest location in the Earths crust itself. ... To help compare different orders of magnitude this page lists lengths between 10 and 100 km (104 to 105 m). ... This article is about the Alpine mountain. ... To help compare different orders of magnitude this page lists lengths between 1 km and 10 km (103 and 104 m). ... 1999 is a common year starting on Friday of the Common Era, and was designated the International Year of Older Persons by the United Nations. ...

Natural resources

• Earth's crust contains large deposits of fossil fuels: (coal, oil, natural gas, methane clathrate). These deposits are used by humans both for energy production and as feedstock for chemical production.
• Mineral ore bodies have been formed in Earth's crust by the action of erosion and plate tectonics. These ore bodies form concentrated sources for many metals and other useful elements.
• Earth's biosphere produces many useful biological products, including (but far from limited to) food, wood, pharmaceuticals, oxygen, and the recycling of many organic wastes. The land-based ecosystem depends upon topsoil and fresh water, and the oceanic ecosystem depends upon dissolved nutrients washed down from the land.

Some of these resources, such as mineral fuels, are difficult to replenish on a short time scale, called non-renewable resources. The exploitation of non-renewable resources by human civilization has become a subject of significant controversy in modern environmentalism movements. Fossil fuels are hydrocarbon-containing natural resources such as coal, petroleum and natural gas. ... Coal is a fossil fuel extracted from the ground either by underground mining, open-pit mining or strip mining. ... Oil is a generic term for organic liquids that are not miscible with water. ... Natural gas - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... Burning ice. Methane released by heating burns, water drips. ... An ore is a mineral deposit containing a metal or other valuable resource in economically viable concentrations. ... Severe soil erosion in a wheat field near Washington State University, USA. Erosion is the displacement of solids (soil, mud, rock, and so forth) by the agents of wind, water, ice, movement in response to gravity, or living organisms (in the case of bioerosion). ... The tectonic plates of the world were mapped in the second half of the 20th century. ... In chemistry, a metal (Greek: Metallon) is an element that readily forms ions (cations) and has metallic bonds, and it is sometimes said that it is similar to a cation in a cloud of electrons. ... A chemical element, often called simply element, is a substance that cannot be divided or changed into different substances by ordinary chemical methods. ... The biosphere is that part of a planet earths outer shell—including air, land, and water—within which life occurs, and which biotic processes in turn alter or transform. ... This article describes the wood that comprises trees and boards. ... Pharmacology (in Greek: pharmacon is drug, and logos is science) is the study of how chemical substances interfere with living systems. ... In ecology, an ecosystem is a community of organisms (plant, animal and other living organisms - also referred as biocenose) together with their environment (or biotope), functioning as a unit. ... Topsoil is the uppermost layer of soil, usually the top six to eight inches. ... <