Ask Jimmy and the Bug

Jimmy and the Bug
there is a picture of Jimmy with his arms in the air with salty fries.

Hey Bug! Taylor C., Grade 4, wants to know: “Why is the ocean salty?”

Seawater contains lots of dissolved chemicals, including the one you shake over your fries. Sodium chloride—better known as table salt—is the most common of all the chemicals found in the ocean. There are about 35 pounds of it in every 1,000 pounds of seawater. That's enough to cover the entire planet with a layer of salt 500 feet high—as tall as a 50-story skyscraper.

there is a drawing of Bug
There is a picture of Bug a TV with a view of mountains and an ocean.

Where does all the salt in the ocean come from? Nature “weathers” rocks and grinds down mountains, releasing locked-in mineral salts. Rain and melting snow carry these chemicals into rivers and out into the sea. Also, hot water (hydrothermal) vents on ridges in the ocean floor pump chemical-rich water into the sea. Even underwater volcanoes add salt to the ocean.

Freshwater in streams, rivers, and lakes contains salt, too—about one pound in a thousand pounds of water. It doesn't taste salty because the concentration, or amount, of dissolved salt is too low for the taste buds on your tongue to detect. In most lakes, water flows in one end and out the other, keeping the salt concentration low. But salt can build up in lakes if they have no outlets. The Great Salt Lake in Utah is 10 times saltier than the ocean. When water flows into the Great Salt Lake, it can't flow out. Some water escapes by evaporation, but the salt it contained is left behind.

there is a drawing of Bug
there is a picture of Jimmy holding a giant salt shaker.

A little salt goes a long way!

Activity

  1. What affects the concentration of salt in a body of freshwater? Why? Explain your answer in a sentence or two.
    [anno: The concentration of salt in a body of freshwater is affected by what kind of outlets that body of water has. If the body of freshwater does not have an outlet, the salt concentration increases as water evaporates.]
  2. Seawater and freshwater are a kind of mixture called a solution. In a solution, two or or more substances are so evenly mixed that the separate parts cannot be seen. As you learned in Lesson 1, a mixture is made up of two or more substances that have been physically combined. Imagine that you looked at a small part of an ocean or a small part of a lake. What kinds of things would you see in the small part of the ocean or lake? What kinds of animals, soil, and plants would would you see? Name at least five things you could see in this mixture.
    [anno: Answers will vary but could include that, in a small part of an ocean, the student might see seawater, coral, fish, sand, and seaweed. In a small part of a lake, the student might see freshwater, grasses, mud, fish, and rocks.]
  3. Now imagine that you looked at another small part of a different ocean or a lake. How do you think the mixture of things would be different? What would make the mixture different in a different place? Explain your answer in a sentence or two.
    [anno: Answers will vary but could include that the mixture of things would be different because there would be different conditions, such as depth and sunlight. Different things might grow and live in a different ocean or lake.]