Why Is The Ocean Salty? - Britannica

Ask the Chatbot Games & Quizzes History & Society Science & Tech Biographies Animals & Nature Geography & Travel Arts & Culture ProCon Money Videos Why Is the Ocean Salty? Introduction References & Edit History Related Topics Images Contents Science Earth Science, Geologic Time & Fossils Earth Sciences

Why Is the Ocean Salty? Why is seawater salty? Ask the Chatbot a Question More Actions Print Cite verifiedCite While every effort has been made to follow citation style rules, there may be some discrepancies. Please refer to the appropriate style manual or other sources if you have any questions. Select Citation Style MLA APA Chicago Manual of Style Copy Citation Share Share Share to social media Facebook X URL https://www.britannica.com/story/why-is-the-ocean-salty Feedback Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback

Our editors will review what you’ve submitted and determine whether to revise the article.

External Websites Ask the Chatbot a Question Written and fact-checked by Britannica Editors Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... Britannica Editors Table of Contents Table of Contents Ask the Chatbot

“Water, water everywhere,/ Nor any drop to drink.” This famous line, spoken by the lost sailor in Samuel Taylor Coleridge’s poem The Rime of the Ancient Mariner, sums up one of the basic difficulties of life at sea: humans need water to survive, but seawater is too salty to drink. In fact, most of Earth is covered with undrinkable water; oceans cover 70 percent of Earth’s surface and account for about 97 percent of all water. The average salt content of ocean water is 35 parts per thousand, which—while it may not sound like much—works out to 120 million tons of salt per cubic mile of seawater. And there are about 332,519,000 cubic miles (1,386,000,000 cubic km) of water in the ocean. Where did all that salt come from?

It comes from the land, mostly. As rain forms and falls through the air, it accumulates carbon dioxide from the atmosphere, causing it to become slightly acidic. It then flows over the land, eroding rocks and picking up small amounts of salt and other dissolved minerals. At this point, the water is still basically fresh; there is some salt in it but usually not enough to make it undrinkable. Eventually, though, most rainwater finds its way to the ocean. Once it gets there, some of the dissolved minerals—such as calcium—are removed from the water by biological processes, but salt tends to remain. Additional salt is contributed by underwater hydrothermal and volcanic activity.

Related Topics: seawater ocean salinity (Show more) See all related content

The idea that salt was gradually deposited in the sea by rivers was first suggested by the British astronomer Edmond Halley in 1715. Halley took his observation a step farther and proposed that salinity of seawater could serve as a kind of clock that could be used to determine the age of the ocean (and thus, he assumed, Earth). He reasoned that dividing the total volume of ocean water by the rate at which salt was deposited in the ocean would show how long it had taken for the ocean to reach its current level of salinity. Measurement techniques weren’t precise enough to perform the calculation in Halley’s time, but the Irish physicist John Joly tried it in 1899, coming up with an estimate of 90 million years. (More-advanced techniques later revealed this to be a major underestimate; the actual age is more like four billion.) Unfortunately, Halley’s scheme had been flawed from the start; among other problems, he had failed to account for the fact that some sea salt becomes sequestered in the form of mineral deposits on the seafloor.

The Editors of Encyclopaedia Britannica