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  2. Earth - Wikipedia

    en.wikipedia.org/wiki/Earth

    Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. 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 Mohorovičić discontinuity. [130]

  3. Geological history of Earth - Wikipedia

    en.wikipedia.org/wiki/Geological_history_of_Earth

    The geological history of the Earth follows the major geological events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left ...

  4. Land snail - Wikipedia

    en.wikipedia.org/wiki/Land_snail

    Land snail. Helix pomatia, a species of air-breathing land snail used for escargot, is a little bit larger than the common garden snail. A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. Land snail is the common name for terrestrial gastropod mollusks that have shells ...

  5. Atmosphere of Earth - Wikipedia

    en.wikipedia.org/wiki/Atmosphere_of_Earth

    Total atmospheric mass is 5.1480×10 18 kg (1.135×10 19 lb), [42] about 2.5% less than would be inferred from the average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure ...

  6. Natural selection - Wikipedia

    en.wikipedia.org/wiki/Natural_selection

    Natural selection acts on an organism's phenotype, or physical characteristics. Phenotype is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives. When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele .

  7. Gaia hypothesis - Wikipedia

    en.wikipedia.org/wiki/Gaia_hypothesis

    The Gaia hypothesis posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. The hypothesis contends that this system as a whole, called Gaia, seeks a physical and chemical environment optimal for contemporary life. [13]

  8. History of Earth - Wikipedia

    en.wikipedia.org/wiki/History_of_Earth

    The first eon in Earth's history, the Hadean, begins with the Earth's formation and is followed by the Archean eon at 3.8 Ga. [2]: 145 The oldest rocks found on Earth date to about 4.0 Ga, and the oldest detrital zircon crystals in rocks to about 4.4 Ga, [34] [35] [36] soon after the formation of the Earth's crust and the Earth itself.

  9. Moon - Wikipedia

    en.wikipedia.org/wiki/Moon

    The usual English proper name for Earth's natural satellite is simply Moon, with a capital M. [19] [20] The noun moon is derived from Old English mōna, which (like all its Germanic cognates) stems from Proto-Germanic *mēnōn, [21] which in turn comes from Proto-Indo-European *mēnsis 'month' [22] (from earlier *mēnōt, genitive *mēneses) which may be related to the verb 'measure' (of time).