WEBVTT - Why Are the Oceans Salty?

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<v Speaker 1>Welcome to brain Stuff from how Stuff Works. Hi, brain Stuff,

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<v Speaker 1>Lauren Vogel bomb here. Anyone who's taken the dunk in

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<v Speaker 1>the ocean is familiar with the shock and mild sting

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<v Speaker 1>the water is so salty. To understand why the seas

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<v Speaker 1>are salty, look no further than the water cycle. Simply put,

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<v Speaker 1>the water cycle begins when fresh water falls from the

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<v Speaker 1>sky in the form of rain. It eventually ends up

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<v Speaker 1>in rivers, lakes, and oceans, where it soon evaporates to

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<v Speaker 1>form clouds and repeat the cycle. If you dig a

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<v Speaker 1>little deeper into each stage of the water cycle, you'll

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<v Speaker 1>see just how salt gets into the mix. That fresh

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<v Speaker 1>water that falls as rain isn't on pure. It mixes

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<v Speaker 1>with the carbon dioxide in the atmosphere on the way down,

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<v Speaker 1>giving it a slightly acidic quality. Once it reaches the

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<v Speaker 1>Earth's surface, it travels over land to reach area waterways.

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<v Speaker 1>As it passes over the land, the acidic nature of

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<v Speaker 1>the water breaks down rocks, capturing ions within these rocks

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<v Speaker 1>and carrying them along to the sea. Roughly. These ions

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<v Speaker 1>are so idium or chloride, which forms salt when they

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<v Speaker 1>banned together. Fresh Water that reaches the ocean evaporates to

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<v Speaker 1>form clouds. However, these sodium, chloride and other ions remain behind,

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<v Speaker 1>where they accumulate over time to give the sea its

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<v Speaker 1>characteristic saltiness. Hydrothermal vents on the ocean floor release additional

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<v Speaker 1>dissolved materials, including more sodium and chloride, further contributing to

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<v Speaker 1>the briny nature of the sea. What surprising is just

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<v Speaker 1>how much the salt from runoff and underwater vents has

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<v Speaker 1>built up since the oceans formed. Dissolved salts make up

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<v Speaker 1>three point five percent of the weight of all ocean water,

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<v Speaker 1>and if you could remove the salt from the sea,

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<v Speaker 1>it would form a layer five hundred feet that's a

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<v Speaker 1>hundred and fifty three meters thick over all of Earth's

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<v Speaker 1>land mass. That's about the height of a forty story building.

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<v Speaker 1>One question, though, if these seas get their salinity from runoff,

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<v Speaker 1>why do lakes remain relatively salt free. For most lakes,

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<v Speaker 1>water flows both in and out of the lake via

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<v Speaker 1>rivers and streams. Salt Ions that end up in the

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<v Speaker 1>water are carried out, keeping the lake fresh. These ions

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<v Speaker 1>eventually end up in oceans, which serve as a dumping

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<v Speaker 1>ground of sorts for runoff and the materials it contains.

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<v Speaker 1>Bodies of water with no outflow, such as the Dead

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<v Speaker 1>Sea or the Great Salt Lake in Utah, maintain a

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<v Speaker 1>level of salinity on par with or higher than that

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<v Speaker 1>of the ocean. Today's episode was written by Vambi Turner

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<v Speaker 1>and produced by Tristan McNeil. For more on this and

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<v Speaker 1>lots of other salty topics, visit our home planet, how

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<v Speaker 1>Stuff works dot com.