Earth - Wikipedia. Earth Orbital characteristics. Epoch. J2. 00. 0. During one orbit around the Sun, Earth rotates about its axis 3. Earth's axis of rotation is tilted 2. Earth's surface is covered with water. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics. Within the first billion years of Earth's history, life appeared in the oceans and began to affect the atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Since then, the combination of Earth's distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive. Life arose on Earth by 3. Over 9. 9% of all species of life. 16-11-2016 1/2 Our Earth Our Earth by Jessica Koehler Click here for Free Registration of Our Earth Book Rated from 95 votes Book ID: 524BEADB59A77FCB94FF666C72CFEBE1 Date of publishing: November 9th, 2016 Number of pages: 128 pages Thank you. Give your child, and all children around the world, a chance to get to discover our earth as we know it today. Give your child a planet or see all WWF gifts previous next WWF Jobs Contact WWF History WWF in Brief Governance WWF Offices What We.Humanity has developed diverse societies and cultures; politically, the world is divided into about 2. Name and etymology. The modern English word Earth developed from a wide variety of Middle English forms. In its earliest appearances, eor. By early Modern English, many nouns were capitalized, and the earth became (and often remained) the Earth, particularly when referenced along with other heavenly bodies. More recently, the name is sometimes simply given as Earth, by analogy with the names of the other planets. Another convention capitalizes . It almost always appears in lowercase in colloquial expressions such as . The formation and evolution of the Solar System bodies occurred along with those of the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets grow out of that disk along with the Sun. A nebula contains gas, ice grains, and dust (including primordial nuclides). According to nebular theory, planetesimals formed by accretion, with the primordial Earth taking 1. Between approximately 4.
The origin of the world's oceans was condensation augmented by water and ice delivered by asteroids, protoplanets, and comets. On time scales lasting hundreds of millions of years, the supercontinents have assembled and broken apart. Roughly 7. 01. 62. The continents later recombined to form Pannotia, 6. High- latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every 4. The last continental glaciation ended 1. A half billion years later, the last common ancestor of all life arose. The resultant molecular oxygen (O2) accumulated in the atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer (O3) in the upper atmosphere. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized Earth's surface. This hypothesis has been termed . Over the past 7. 01. The development of agriculture, and then civilization, led to humans having an influence on Earth and the nature and quantity of other life forms that continues today. Over the next 7. 01. From that point, the Earth is expected to be habitable for another 7. Models predict that the Sun will expand to roughly 1 AU (1. As a red giant, the Sun will lose roughly 3. Earth will move to an orbit 1. AU from the Sun when the star reaches its maximum radius. Most, if not all, remaining life will be destroyed by the Sun's increased luminosity (peaking at about 5,0. Shown are distances between surface relief and the geocentre. The South American Andes summits are visible as elevated areas. Data from the Earth. Due to rotation, the Earth is flattened along the geographic axis and bulging around the equator. Local topography deviates from this idealized spheroid, although on a global scale these deviations are small compared to Earth's radius: The maximum deviation of only 0. Mariana Trench (1. Mount Everest (8,8. It is composed mostly of iron (3. Due to mass segregation, the core region is estimated to be primarily composed of iron (8. The principal oxides are silica, alumina, iron oxides, lime, magnesia, potash and soda. The silica functions principally as an acid, forming silicates, and all the most common minerals of igneous rocks are of this nature. The outer layer is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovi. The thickness of the crust varies from about 7. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, and it is of the lithosphere that the tectonic plates are composed. Beneath the lithosphere is the asthenosphere, a relatively low- viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 4. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core. This extra heat production, twice present- day at approximately 7. These plumes can produce hotspots and flood basalts. The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans because the crust there is much thinner than that of the continents. These plates are rigid segments that move in relation to one another at one of three types of plate boundaries: convergent boundaries, at which two plates come together, divergent boundaries, at which two plates are pulled apart, and transform boundaries, in which two plates slide past one another laterally. Earthquakes, volcanic activity, mountain- building, and oceanic trench formation can occur along these plate boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid- ocean ridges. The combination of these processes recycles the oceanic crust back into the mantle. Due to this recycling, most of the ocean floor is less than 7. The oldest oceanic crust is located in the Western Pacific, and has an estimated age of 7. Other notable plates include the Arabian Plate, the Caribbean Plate, the Nazca Plate off the west coast of South America and the Scotia Plate in the southern Atlantic Ocean. The Australian Plate fused with the Indian Plate between 5. The fastest- moving plates are the oceanic plates, with the Cocos Plate advancing at a rate of 7. At the other extreme, the slowest- moving plate is the Eurasian Plate, progressing at a typical rate of 2. The remaining 2. 9. Tectonics and erosion, volcanic eruptions, flooding, weathering, glaciation, the growth of coral reefs, and meteorite impacts are among the processes that constantly reshaping and have reshaped the Earth's surface over geological time. Less common is basalt, a denser volcanic rock that is the primary constituent of the ocean floors. Nearly 7. 5% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the crust. The most abundant silicate minerals on Earth's surface include quartz, feldspars, amphibole, mica, pyroxene and olivine. The mean height of land above sea level is 8. The total arable land is 1. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,0. The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean with a depth of 1. The oceans cover an area of 7. Most fresh water, about 6. The height of the troposphere varies with latitude, ranging between 8 km at the poles to 1. Oxygenic photosynthesis evolved 7. The ozone layer blocks ultravioletsolar radiation, permitting life on land. Water vapor, carbon dioxide, methane and ozone are the primary greenhouse gases in the atmosphere. Without this heat- retention effect, the average surface temperature would be . Three- quarters of the atmosphere's mass is contained within the first 1. This lowest layer is called the troposphere. Energy from the Sun heats this layer, and the surface below, causing expansion of the air. This lower- density air then rises, and is replaced by cooler, higher- density air. The result is atmospheric circulation that drives the weather and climate through redistribution of thermal energy. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and falls to the surface as precipitation. This water cycle is a vital mechanism for supporting life on land, and is a primary factor in the erosion of surface features over geological periods. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter. Atmospheric circulation, topographic features and temperature differences determine the average precipitation that falls in each region. At higher latitudes the sunlight reaches the surface at lower angles and it must pass through thicker columns of the atmosphere. As a result, the mean annual air temperature at sea level decreases by about 0. Ranging from the equator to the polar regions, these are the tropical (or equatorial), subtropical, temperate and polar climates. For example, the Scandinavian peninsula has more moderate climate than similarly northern latitudes of northern Canada. The wind enables this moderating effect. The windward side of a land mass experiences more moderation than the leeward side. In the Northern Hemisphere, the prevailing wind is west- to- east, and western coasts tend to be milder than eastern coasts. This is seen in Eastern North America and Western Europe, where rough continental climates appear on the east coast on parallels with mild climates on the other side of the ocean. The Earth is closest to the sun (at perihelion) in January, which is summer in the Southern Hemisphere. It is furthest away (at aphelion) in July, which is summer in the Northern Hemisphere, and only 9. Sun falls on a given square area of land than at perihelion. Despite this, there are larger land masses in the Northern Hemisphere, which are easier to heat than the seas.
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