, The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. According to nebular theory, planetesimals formed by accretion, with the primordial Earth being estimated as likely taking anywhere from 70–100 million years to form.  Atmospheric circulation also plays an important role: San Francisco and Washington DC are both coastal cities at about the same latitude. The first continental crust, which was more felsic in composition, formed by the partial melting of this mafic crust. In addition to an annual component to this motion, there is a 14-month cycle called the Chandler wobble. Due to mass segregation, the core region is estimated to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulphur (4.5%), and less than 1% trace elements.  Sea ice in the Arctic covers an area about as big as the United States, although it is quickly retreating as a consequence of climate change.  This is driving changes such as the melting of glaciers and ice sheets, a global rise in average sea levels, and significant shifts in weather. , The continental crust consists of lower density material such as the igneous rocks granite and andesite. Due to this recycling, most of the ocean floor is less than 100 Ma old.  About 97.5% of the water is saline; the remaining 2.5% is fresh water. focis. According to radiometric dating estimation and other evidence, Earth formed over 4.5 billion years ago. , Earth's atmosphere has no definite boundary, slowly becoming thinner and fading into outer space. The continents later recombined to form Pannotia at 600–540 Ma, then finally Pangaea, which also began to break apart at 180 Ma. 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.  Between approximately 4.1 and 3.8 Ga, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon and, by inference, to that of Earth. terrestris adjective. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and falls to the surface as precipitation. , Further factors that affect a location's climates are its proximity to oceans, the oceanic and atmospheric circulation, and topology. ", Monthly Notices of the Royal Astronomical Society, "Hope dims that Earth will survive Sun's death", "Converting GPS Height into NAVD88 Elevation with the GEOID96 Geoid Height Model", "Exploring the Ocean Basins with Satellite Altimeter Data", "Did Edmund Hillary Climb the Wrong Mountain", "The five deeps: The location and depth of the deepest place in each of the world's oceans", "Is a Pool Ball Smoother than the Earth?  There is a scientific consensus that humans are causing global warming by releasing greenhouse gases into the atmosphere. 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 0.17% is at the Mariana Trench (10,925 metres or 35,843 feet below local sea level), whereas Mount Everest (8,848 metres or 29,029 feet above local sea level) represents a deviation of 0.14%. The two models and the data that support them can be reconciled by large-scale recycling of the continental crust, particularly during the early stages of Earth's history. Earth that's "firma". There are at least five quasi-satellites, including 469219 Kamoʻoalewa.  Apart from the proposed current Holocene extinction event, the most recent was 66 Ma, when an asteroid impact triggered the extinction of the non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, mammals, lizards and birds. , The pedosphere is the outermost layer of Earth's continental surface and is composed of soil and subject to soil formation processes. Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Observable universe → UniverseEach arrow (→) may be read as "within" or "part of". One of the Latin equivalents of the English word 'earth' is Terra.  The standard astronomical symbol of Earth consists of a cross circumscribed by a circle, , representing the four corners of the world. Almost 8 billion humans live on Earth and depend on its biosphere and natural resources for their survival.