Water - On Earth

On Earth

Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology.

The collective mass of water found on, under, and over the surface of a planet is called the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1,338,000,000 km3 (321,000,000 mi3).

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 sea water. Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers.

Water is important in many geological processes. Groundwater is present in most rocks, and the pressure of this groundwater affects patterns of faulting. Water in the mantle is responsible for the melt that produces volcanoes at subduction zones. On the surface of the Earth, water is important in both chemical and physical weathering processes. Water and, to a lesser but still significant extent, ice, are also responsible for a large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks, which make up the geologic record of Earth history.

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Famous quotes containing the word earth:

    Have We not made the earth as a cradle and the mountains as pegs? And We created you in pairs, and We appointed your sleep for a rest; and We appointed night for a garment, and We appointed day for a livelihood. And We have built above you seven strong ones, and We appointed a blazing lamp and have sent down out of the rain-clouds water cascading that We may bring forth thereby grain and plants, and gardens luxuriant.
    —Qur’An. “The Tiding,” 78:6-16, trans. by Arthur J. Arberry (1955)

    I am not aware that any man has ever built on the spot which I occupy. Deliver me from a city built on the site of a more ancient city, whose materials are ruins, whose gardens cemeteries. The soil is blanched and accursed there, and before that becomes necessary the earth itself will be destroyed.
    Henry David Thoreau (1817–1862)