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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.
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.
The Encyclopedia of Earth (abbreviated EoE) is an electronic reference about the Earth, its natural environments, and their interaction with society.The Encyclopedia is described as a free, fully searchable collection of articles written by scholars, professionals, educators, and other approved [who?] experts, who collaborate and review each other's work.
Earth's crust and mantle, Mohorovičić discontinuity between bottom of crust and solid uppermost mantle. Earth's mantle extends to a depth of 2,890 km (1,800 mi), making it the planet's thickest layer. [20] [This is 45% of the 6,371 km (3,959 mi) radius, and 83.7% of the volume - 0.6% of the volume is the crust].
The Earth of the early Archean may have had a different tectonic style. It is widely believed that the early Earth was dominated by vertical tectonic processes, such as stagnant lid , [ 19 ] [ 20 ] heat-pipe , [ 21 ] or sagduction , [ 22 ] [ 23 ] [ 24 ] which eventually transitioned to plate tectonics during the planet's mid-stage evolution.
the Earth's mass, its gravitational field, and its angular inertia. These are all affected by the density and dimensions of the inner layers. [20] the natural oscillation frequencies and modes of the whole Earth oscillations, when large earthquakes make the planet "ring" like a bell. These oscillations also depend strongly on the inner layers ...
Land is often defined as the solid, dry surface of Earth. [1] The word land may also collectively refer the collective natural resources of Earth, [2] including its land cover, rivers, shallow lakes, its biosphere, the lowest layer of the atmosphere (troposphere), groundwater reserves, and the physical results of human activity on land, such as architecture and agriculture. [3]
Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically since the start of the 20th century. Initially, Earth was believed to be the center of the Universe , which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars . [ 1 ]