Core Concepts and Underlying Logic from 'The Sea Is Salty'

I wonder why the sea is salty and other questions about the oceans. How big is the ocean? The ocean is truly enormous. It covers more than once as much of the earth as land does. In fact, it is made up of four oceans, the Pacific, the Atlantic, the Indian, and the Arctic. Although these all have different names, they flew into each other to make one huge world ocean. Don't go for a swim in the Antarctic ocean. It is the coast of the oceans, and for most of the year it is covered in ice. Which is the biggest ocean? The Pacific is by far the biggest ocean in the world. It is larger than the other three oceans put together, and it is also much deeper. If you look at the globe, you'll see that the Pacific reaches halfway around the world. What is the difference between a sea and an ocean? People often use the world sea and ocean to mean the same thing. That's fine, but to a scientist, seas are just a part of the ocean. The parts that are nearest to land. The Caribbean Sea is between Central America and the Caribbean Islands, for example. Why is the sea salty? Sea water tastes the salty because it has salt in it. The salt is the same as the stuffed people sprinkle on food. Most of it comes from rocks on the land. Spring washes the salt into rivers, which carry it to the sea. Most of the earth water is salty, only a tiny part is fresh water that we can drink. Some of the sea salt we use comes from hot places such as India. People build low walls to trap the sea water when the tide comes in. When the sun dries up the water, the salt is left behind. If the red sea really red, parts of the red sea look red in summer. In summer, millions of tiny red plants called algae grow in the water. Don't worry, you won't turn pink if you swim there. Some beaches around the black sea are covered with rich, dark mud. People slap it all over themselves. It's meant to be good for the skin. What did sailors fear the most? In Odendays, sailors had to put up with bad food, fearful stones,