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The origin of water on Earth is the subject of a body of research in the fields of planetary science, astronomy, and astrobiology. Earth is unique among the rocky planets in the Solar System in having oceans of liquid water on its surface. [2] Liquid water, which is necessary for all known forms of life, continues to exist on the surface of ...
Earth's approximate water volume (the total water supply of the world) is 1.386 billion cubic kilometres (333 million cubic miles). [23] Liquid water is found in bodies of water, such as an ocean, sea, lake, river, stream, canal, pond, or puddle. The majority of water on Earth is seawater.
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 ...
The total volume of water on Earth is estimated at 1.386 billion km 3 (333 million cubic miles), with 97.5% being salt water and 2.5% being freshwater. Of the freshwater, only 0.3% is in liquid form on the surface. [2][3][4] Because the oceans that cover roughly 70.8% of the area of Earth reflect blue light, Earth appears blue from space, and ...
The water cycle (or hydrologic cycle or hydrological cycle), is a biogeochemical cycle that involves the continuous movement of water on, above and below the surface of the Earth. The mass of water on Earth remains fairly constant over time. However, the partitioning of the water into the major reservoirs of ice, fresh water, salt water and ...
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
Most of Earth's surface is ocean water: 70.8% or 361 million km 2 (139 million sq mi). [96] This vast pool of salty water is often called the world ocean, [97] [98] and makes Earth with its dynamic hydrosphere a water world [99] [100] or ocean world. [101] [102] Indeed, in Earth's early history the ocean may have covered Earth completely. [103]
Hydrosphere. The hydrosphere (from Ancient Greek ὕδωρ (húdōr) 'water' and σφαῖρα (sphaîra) 'sphere') [1][2] is the combined mass of water found on, under, and above the surface of a planet, minor planet, or natural satellite. Although Earth 's hydrosphere has been around for about 4 billion years, [3][4] it continues to change in ...