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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 ...
Earth is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System. Of the four rocky planets, it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it, taking a year (about 365.25 days) to complete one revolution.
Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science discipline concerned with the geology of celestial bodies such as planets and their moons, asteroids, comets, and meteorites. [1] [2] Although the geo- prefix typically indicates topics of or relating to Earth, planetary geology is named as such for ...
Planetary science. A geological map of the Sputnik Planitia basin on the dwarf planet Pluto. Analysis of planetary surfaces and surface features is a major component of planetary science. Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth ), celestial bodies (such as moons, asteroids, comets) and ...
The geology of solar terrestrial planets mainly deals with the geological aspects of the four terrestrial planets of the Solar System – Mercury, Venus, Earth, and Mars – and one terrestrial dwarf planet: Ceres. Earth is the only terrestrial planet known to have an active hydrosphere. Terrestrial planets are substantially different from the ...
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [ 32][ 33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some ...
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs . Eon.
outer core–inner core boundary. Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 20% of Earth’s radius or 70% of the Moon 's radius. [ 1][ 2] There are no samples of Earth's core accessible for direct measurement, as there are for ...