Cartography is about more than just navigation. For hundreds of years, maps have served as important repositories of knowledge. Thinking of them as merely a representation of how to get from point A to point B obscures much of their value. A good map can contain large amounts of geographical, historical, scientific, political, and other types of data. It is simply a matter of understanding how to mine that information from what some people see as a simple navigational tool or pretty piece of artwork.
Take for example an Oceans and Seas Map. Really studying such a map can reveal a wealth of information about oceans, seas, and the lands they surround. Remember that the earth is over seventy percent water and most of that water is contained in five major oceans, with the remainder making up lesser oceans and seas as well as fresh water rivers and lakes. All in all, water covers 361.132 million square kilometers of the planet.
A map makes it easy to rank the five oceans by size. The Pacific Ocean is clearly the biggest, covering over 155 million square kilometers. It is followed by the Atlantic (76 million sq km), the Indian Ocean (68 million sq km) and the Southern Ocean (20 million sq km). These four oceans are the largest bodies of any kind in the world. The largest country, Russia, ranks below them, but comes in just before the final major ocean, the Arctic (14 million sq km).
Viewing a map, one can trace the 356,00 kilometers of coastline in the world. This includes the 94 countries that are purely islands. Many of these are actually island chains and many mainland countries incorporate islands as part of their territory. There are 178 islands that are larger than 2500 square kilometers (970 square miles). Greenland tops the list at over 2.1 million square kilometers (822,706 square miles). There are literally hundreds of islands smaller than 2500 kilometers and many islands are too small to be named or counted.
An ocean map may also reveal the depth of water, display ocean currents, major ports, and even show the points where major rivers bring fresh water to the sea. The lowest point on the planet is underwater. It is the Challenger Deep, which descends 10,924 meters below the surface. It is part of the Mariana Trench in the Pacific Ocean. Contrast this with the 8,848 meter elevation of Mount Everest, the highest point in the world and it is easy to see that there is so much more to the oceans of the world than can be imagined by looking at the surface.