A sea is a body of water made up of salt water. A large part of the earth is covered with seawater, more than two-thirds. There are individual parts, but they are all connected. This is called the “Sea of the World”. It is usually divided into five oceans.
In addition, parts of an ocean also have special names, such as contiguous seas and bays. The Mediterranean Sea is an example of this or the Caribbean. The Red Sea between Egypt and Arabia is more of a side sea that is almost completely landlocked.
The surface of the earth is mainly covered with the seas: It is about 71 percent, i.e. almost three-quarters. The deepest point is in the Mariana Trench in the Pacific Ocean. It’s about eleven thousand meters deep there.
What exactly is a sea, and what is it called like that?
If a body of water is completely surrounded by land, then it is not a sea but a lake. Some lakes are still called seas. This can have two different reasons.
The Caspian Sea is actually a salt lake. This also applies to the Dead Sea. They got their name because of their size: to the people, they seemed as big as a sea.
In Germany, there is another, very specific reason. In German, we usually say Meer for part of the ocean and See for standing inland water. In Low German, however, it is the other way around. This has partly found its way into the standard German language.
That’s why we also say “the sea” for a sea: the North Sea, the Baltic Sea, the South Sea, and so on. There are also some lakes in northern Germany that have the word “sea” in their names. The best known is probably the Steinhuder Meer in Lower Saxony, the largest lake in the north.
What oceans are there?
The world sea is usually divided into five oceans. The largest is the Pacific Ocean between America and Asia. It is also simply called the Pacific. The second largest is the Atlantic Ocean or Atlantic Ocean between Europe and Africa to the east and America to the west. The third largest is the Indian Ocean between Africa, India, and Australia.
The fourth largest is the Southern Ocean. This is the area around the mainland of Antarctica. The smallest of the five is the Arctic Ocean. It lies beneath the arctic ice and reaches Canada and Russia.
Some people speak of the seven seas. In addition to the five oceans, they add two seas that are close to them or that they often travel by ship. Common examples are the Mediterranean Sea and the Caribbean.
In ancient times, people also reckoned with seven seas. These were six parts of the Mediterranean like the Adriatic Sea plus the Black Sea. Each epoch had its own way of counting. This was strongly related to which seas were known at all.
Why are the seas so important?
Many people live by the sea: they catch fish there, receive tourists or they sail the seas to transport goods. The seabed contains raw materials such as crude oil, which is extracted.
Last but not least, the sea is important for the climate of our planet Earth. The oceans store heat, distribute it via currents, and also absorb greenhouse gases such as carbon dioxide. So without them, we would have more global warming.
However, a lot of carbon dioxide is also bad for the oceans. In seawater, it becomes carbonic acid. This makes the oceans acidic, which is bad for many water bodies.
Environmentalists are also concerned that more and more garbage is ending up in the sea. Plastic in particular degrades very slowly. However, it decomposes into very small pieces, the microplastics. This allows it to end up in the bodies of animals and cause damage there.
How does the salt get into the sea?
Nowhere on earth is there as much water as in the oceans: 97 percent. However, the sea water is not drinkable. On some coasts, there are plants for the desalination of seawater, which turns it into drinking water.
Salts are found in rocks all over the world. In connection with the sea, one usually speaks of table salt or common salt, which we use in the kitchen. Table salt dissolves very well in water. Even small amounts get into the sea through the rivers.
There is also salt on the seabed. That too is slowly sinking into the water. Volcanoes on the ocean floor can also emit salt. Earthquakes on the seabed also cause salt to enter the water.
The water cycle causes a lot of water to enter the ocean. However, it can only leave the sea again through evaporation. The salt doesn’t go with it. Salt, once in the sea, stays there. The more water evaporates, the more saline the sea becomes. Therefore, the salinity is not exactly the same in every sea.
A liter of seawater usually contains around 35 grams of salt. That’s about a heaped tablespoon and a half. We usually fill about 150 liters of water in a bathtub. So you would have to add about five kilograms of salt to get seawater.