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  2. Internal structure of Earth - Wikipedia

    en.wikipedia.org/wiki/Internal_structure_of_Earth

    The internal structure of Earth are the layers of the Earth, excluding its atmosphere and hydrosphere. The structure consists of an outer silicate solid crust, a highly viscous asthenosphere, and solid mantle, a liquid outer core whose flow generates the Earth's magnetic field, and a solid inner core. Scientific understanding of the internal ...

  3. Earth's outer core - Wikipedia

    en.wikipedia.org/wiki/Earth's_outer_core

    Earth's outer core is a fluid layer about 2,260 km (1,400 mi) thick, composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [1][2][3] The outer core begins approximately 2,889 km (1,795 mi) beneath Earth's surface at the core-mantle boundary and ends 5,150 km (3,200 mi) beneath Earth's surface at the ...

  4. Solar System - Wikipedia

    en.wikipedia.org/wiki/Solar_System

    720,000 km/h (450,000 mi/h) [10] Orbital period. ~230 million years [10] The Solar System[d] is the gravitationally bound system of the Sun and the objects that orbit it. [11] It formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.

  5. Ionosphere - Wikipedia

    en.wikipedia.org/wiki/Ionosphere

    Ionosphere. The ionosphere (/ aɪˈɒnəˌsfɪər /) [1][2] is the ionized part of the upper atmosphere of Earth, from about 48 km (30 mi) to 965 km (600 mi) above sea level, [3] a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation.

  6. Human embryonic development - Wikipedia

    en.wikipedia.org/wiki/Human_embryonic_development

    Human embryonic development or human embryogenesis is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of development. In biological terms, the development of the human body entails growth from a one-celled ...

  7. Atmosphere - Wikipedia

    en.wikipedia.org/wiki/Atmosphere

    The troposphere is the lowest layer of the atmosphere. This extends from the planetary surface to the bottom of the stratosphere. The troposphere contains 75–80% of the mass of the atmosphere, [9] and is the atmospheric layer wherein the weather occurs; the height of the troposphere varies between 17 km at the equator and 7.0 km at the poles.

  8. Onion model - Wikipedia

    en.wikipedia.org/wiki/Onion_model

    An onion model used in social penetration theory. The onion model is a graph-based diagram and conceptual model for describing relationships among levels of a hierarchy, evoking a metaphor of the layered "shells" exposed when an onion (or other concentric assembly of spheroidal objects) is bisected by a plane that intersects the center or the innermost shell.

  9. Outline of Earth sciences - Wikipedia

    en.wikipedia.org/wiki/Outline_of_Earth_sciences

    Pedosphere – The outermost layer of the Earth that is composed of soil and subject to soil formation processes. Outer layers. By composition. Crust (geology) – The outermost solid shell of a rocky planet, dwarf planet, or natural satellite. Moho Discontinuity – The line between the crust and the Earth's mantle.