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The abundance of water on Earth's surface is a unique feature that distinguishes the "[[Blue Planet]]" from others in the solar system. The Earth's hydrosphere consists chiefly of the [[oceans]], but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 m. The deepest underwater location is Challenger Deep of the [[Mariana Trench]] in the [[Pacific Ocean]] with a depth of −10,911 m (35,798 ft or 6.78 mi). [http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html] "Deep Ocean Studies", Ocean Studies, RAIN National Public Internet and Community Technology Center, Takuyo measurement; see [[Mariana Trench]] for details. The average depth of the oceans is 3,794 m (12,447 ft), more than five times the average height of the continents.

The abundance of water on Earth's surface is a unique feature that distinguishes the "[[Blue Planet]]" from others in the solar system. The Earth's hydrosphere consists chiefly of the [[oceans]], but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 m. The deepest underwater location is Challenger Deep of the [[Mariana Trench]] in the [[Pacific Ocean]] with a depth of −10,911 m (35,798 ft or 6.78 mi). [http://www.rain.org/ocean/ocean-studies-challenger-deep-mariana-trench.html] "Deep Ocean Studies", Ocean Studies, RAIN National Public Internet and Community Technology Center, Takuyo measurement; see [[Mariana Trench]] for details. The average depth of the oceans is 3,794 m (12,447 ft), more than five times the average height of the continents.

The mass of the oceans is approximately 1.35 e|18 ;metric tons, or about 1/4400 of the total mass of the Earth, and occupies a volume of 1.386 e|9 km³. If all of the land on Earth were spread evenly, water would rise to an altitude of more than 2.7 km (approximately 1.7 mi). The total volume of the Earth's oceans is: 1.4{{e|9}} km³. The total surface area of the Earth is 5.1{{e|8}} km². So, to [[Orders of approximation|first approximation]], the average depth would be the ratio of the two, or 2.7km. About 97.5% of the water is saline, while the remaining 2.5% is fresh water. The majority of the fresh water, about 68.7%, is currently in the form of ice.Igor A. Shiklomanov, [http://espejo.unesco.org.uy] World Water Resources and their use Beginning of the 21st century" Prepared in the Framework of IHP UNESCO, State Hydrological Institute, St. Petersburg.

The mass of the oceans is approximately 1.35 e|18 ;metric tons, or about 1/4400 of the total mass of the Earth, and occupies a volume of 1.386 e|9 km³. If all of the land on Earth were spread evenly, water would rise to an altitude of more than 2.7 km (approximately 1.7 mi). The total volume of the Earth's oceans is: 1.4 km³. The total surface area of the Earth is 5.1 km². So, to [[Orders of approximation|first approximation]], the average depth would be the ratio of the two, or 2.7km. About 97.5% of the water is saline, while the remaining 2.5% is fresh water. The majority of the fresh water, about 68.7%, is currently in the form of ice.Igor A. Shiklomanov, [http://espejo.unesco.org.uy] World Water Resources and their use Beginning of the 21st century" Prepared in the Framework of IHP UNESCO, State Hydrological Institute, St. Petersburg.

About 3.5% of the total mass of the oceans consists of [[salt]]. Most of this salt was released from volcanic activity or extracted from cool, igneous rocks.[http://www.astrobio.net/news/article223.html],Salt of the Early Earth,NASA Astrobiology Magazine. The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. [http://seis.natsci.csulb.edu/rmorris/oxy/oxy4.html] NASA Astrobiology Magazine, Sea water has an important influence on the world's

About 3.5% of the total mass of the oceans consists of [[salt]]. Most of this salt was released from volcanic activity or extracted from cool, igneous rocks.[http://www.astrobio.net/news/article223.html],Salt of the Early Earth,NASA Astrobiology Magazine. The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. [http://seis.natsci.csulb.edu/rmorris/oxy/oxy4.html] NASA Astrobiology Magazine, Sea water has an important influence on the world's