One of the most frequently searched questions on Google is “Why is the ocean salty?” Well, a better question might be, “why is any water in nature salty?” It is a pertinent question, as about 97% of Earth’s water is salty, which leaves us with not so much water to actually drink. This water also covers about 70% of the surface of Earth. In light of this importance, this essay will explore the reasons behind the salt content of ocean water and seawater.
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Let us go over the main question first: why is the ocean salty? To break it down simply, oceans become salty due to rocks on land. This seems like a strange answer but as the National Ocean Service explains, it is quite logical: “The rain that falls on the land contains some dissolved carbon dioxide from the surrounding air. This causes the rainwater to be slightly acidic due to carbonic acid (which forms from carbon dioxide and water). As the rain erodes the rock, acids in the rainwater break down the rock” (US Department of Commerce, and National Oceanic and Atmospheric Administration). To further explain, this process creates electrically charged atomic particles called ions. These ions go into streams and rivers and end up eventually in the ocean. A majority of these ions are messed with by organisms and are removed. However, some of the ions are left in the water and begin to build up into concentrations. The most common ions in ocean water and seawater are Chloride and Sodium, both of which are salty in taste.
When this slightly acidic rain beats down on mineralized rocks and travels ultimately to the ocean, salty substances tend to remain. This process is called weathering. According to the University of Texas at Dallas, “Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean. Because of the huge volume of the oceans, hundreds of millions of years of river input were required for the salt content to build to its present level” (Pujana, Ignacio). However, the saltiness of water is not only provided by water from rivers and streams.
Another reason ocean water becomes salty is due to hydrothermal vents. As the University of Texas at Dallas states, “About twenty years ago, features on the crest of oceanic ridges were discovered that modified our view on how the sea became salty. These features, known as hydrothermal vents, represent places on the ocean floor where sea water that has seeped into the rocks of the oceanic crust, has become hotter, and has dissolved some of the minerals from the crust, now flows back into the ocean. With the hot water comes a large complement of dissolved minerals” (Pujana, Ignacio). It is estimated that these hydrothermal vents have been in this process for millions of years, and are a partial result of the salinity of ocean water.
Lastly, the saltiness of water is also affected by submarine volcanoes. With the eruption of underwater volcanoes, the water reacts to the hot rock and a dissolving process happens where minerals are left in the water. However, it is difficult to measure how much of the salt in the ocean comes from this activity (Pujana, Ignacio).
Lakes have an additional element to them that makes their salt content more pronounced. These bodies of water could be said to be large depressions in a river channel, and some of them have only a small outlet, or no outlet at all. As the University of Texas at Dallas explains, “The Great Salt Lake, Dead Sea, and other salt lakes have no outlets. All the water that flows into these lakes escapes only by evaporation. When water evaporates, the dissolved salts are left behind” (Pujana, Ignacio). Though the ocean is in a static state in term of salinity, lakes like these will continue to increase in their salt content.
To summarize, the salt in oceans is caused by the collection of minerals from rain beating down on mineralized rocks and transposing these contents into streams and rivers that eventually meet the ocean, plus submarine volcanic activity and hydrothermal vents. Lakes have similar salt content due to these reasons, but also act as depressions where salt can easily collect due to a small outlet or no outlet at all. Lastly, evaporation sometimes aides in the process of keeping salt content stable or increasing it.
US Department of Commerce, and National Oceanic and Atmospheric Administration. “Why Is the Ocean Salty?” NOAA’s National Ocean Service, 14 Nov. 2008, oceanservice.noaa.gov/facts/whysalty.html.
Britannica, The Editors of Encyclopaedia. “Why Is the Ocean Salty?” Encyclopædia Britannica, Encyclopædia Britannica, Inc., www.britannica.com/story/why-is-the-ocean-salty.
Pujana, Ignacio. “Why is the sea salty?” www.utdallas.edu/~pujana/oceans/why.html.
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