WEBVTT - BrainStuff Classics: Why Are the Oceans Salty?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,

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<v Speaker 1>I'm Lauren vogel Bomb, and today's episode is another classic

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<v Speaker 1>from our archive. Today's question is fairly direct. Why are

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<v Speaker 1>Earth's oceans and select other bodies of water salty whereas

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<v Speaker 1>rivers and most lakes are fresh? Hi brain Stuff, Lauren

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<v Speaker 1>vogel Bomb. Here. Anyone who's taken a dunk in the

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

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

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

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

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<v Speaker 1>in the form of rain. It eventually ends up in rivers, lakes,

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<v Speaker 1>and oceans, where it soon evaporates to form clouds and

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<v Speaker 1>repeat the cycle. If you dig a little deeper into

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<v Speaker 1>each stage of the water cycle, you'll see just how

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<v Speaker 1>salt gets into the mix. That fresh water that falls

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<v Speaker 1>as rain isn't pure. It mixes with the carbon dioxide

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<v Speaker 1>in the atmosphere on the way down, giving it a

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<v Speaker 1>slightly acidic quality. Once it reaches the Earth's surface, it

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<v Speaker 1>travels over land to reach area waterways. As it passes

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<v Speaker 1>over the land, the acidic nature of the water breaks

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<v Speaker 1>down rocks, capturing ions within these rocks and carrying them

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<v Speaker 1>along to the sea. Roughly of these ions are sodium

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<v Speaker 1>or chloride, which forms salt when they band together. Fresh

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<v Speaker 1>water that reaches the ocean evaporates to form clouds. However,

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<v Speaker 1>these sodium, chloride and other ions remain behind, where they

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<v Speaker 1>accumulate over time to give the sea its characteristic saltiness.

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<v Speaker 1>Hydrothermal vents on the ocean floor release additional dissolved materials,

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<v Speaker 1>including more sodium and chloride, further contributing to the briny

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<v Speaker 1>nature of the sea. What's surprising is just how much

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<v Speaker 1>the salt from runoff and underwater vents has built up

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

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

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

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

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

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<v Speaker 1>That's about the height of a forty story building. One question, though,

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<v Speaker 1>if these seas get their salinity from runoff, why do

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<v Speaker 1>lakes remain relatively salt free for most lakes. Water flows

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<v Speaker 1>both in and out of the lake via rivers and streams.

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<v Speaker 1>Salt Ions that end up in the water are carried out,

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<v Speaker 1>keeping the lake fresh. These ions eventually end up in oceans,

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<v Speaker 1>which serve as a dumping ground of sorts for runoff

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<v Speaker 1>and the materials it contains. Bodies of water with no outflow,

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<v Speaker 1>such as the Dead Sea or the Great Salt Lake

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<v Speaker 1>in Utah, maintain a level of salinity on par with

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<v Speaker 1>or higher than that of the ocean. Today's episode was

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<v Speaker 1>originally produced by Tristan McNeil and is based on the

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<v Speaker 1>article why is seawater salty? On how stuff works dot

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<v Speaker 1>Com written by Bambi Turner. Brain Stuff is production of

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<v Speaker 1>by Heart Radio in partnership with how stuffworks dot Com

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<v Speaker 1>and is produced by Tylor Clang. Four more podcasts. My

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<v Speaker 1>heart Radio isn't the iHeart Radio app, Apple Podcasts or

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<v Speaker 1>wherever you listen into your favorite shows