How many continents are there?


A continent is a landmass with specific characteristics. Each continent is unique, but they are all characterized by two features: ancient, geologically stable regions and younger geologically active areas. The great mountain ranges of the continents are found in these younger regions. Most have extensive plains or plateaus. All of the continents, except Antarctica, are "wedge-shaped," wider at the north than at the south.

By convention there are seven continents: Asia, Africa, North America, South America, Europe, Australia, and Antarctica. Some geographers list only six continents, combining Europe and Asia into Eurasia. In parts of the world, students learn that there are just five continents: Eurasia, Australia, Africa, Antarctica, and the Americas.

To some geographers, however, "continent" is not just a physical term; it also carries cultural connotations. For example, Europe and Asia are physically part of the same landmass, but the two areas are culturally diverse. (That is, the various cultural groups in Asia have more in common with one another than with those of Europe.)

Islands located near a continent are generally considered, in a geographical sense, part of that continent. Greenland, for example, is politically part of Europe but belongs geographically to North America, as do the islands of the Caribbean and the western North Atlantic Ocean. There are some islands and island groups, however, that are not considered part of any continent, geographically speaking. New Zealand, Hawaii, and French Polynesia are among them.

Oceania is the collective name for the lands of the Pacific Ocean, including Melanesia, Micronesia, and Polynesia. Oceania is a convenient way to name these areas, which, with the exception of Australia, are not part of any continent. But Oceania itself is not a continent.


How many oceans are there?


There is really only one world ocean; for convenience, most geographers divide it into four: Atlantic, Pacific, Arctic, and Indian.


What is the world's longest river?


The Nile is now considered the longest river in the world. At one time, the Para River was considered to be part of the Amazon's mouth, so when added to the length of the Amazon, its distance exceeded that of the Nile. Most geographers now agree that the opposite is true, that the true mouth is on the north side of the Island of Marajo, where it flows straight through the Canal de Norte and out into the Atlantic.

Nile River: 4,238 miles (6,825 kilometers)
Amazon River: 4,000 miles (6,437 kilometers)


What is the world's tallest mountain?


Mount Everest holds that distinction, with an elevation of 29,035 feet (8,850 meters).


How many countries are there in the world?


At last count, there were 193 independent countries. National Geographic's online Travel and Cultures database includes maps, country profiles, photographs, fast facts, music, and other information. The Maps site has interactive and printable maps.


What is the world's largest desert?


Most experts agree that a desert is an area of land that receives 10 inches (25.4 centimeters) or less of precipitation per year. The world's deserts can be categorized into five kinds, according to the causes of their dryness: subtropical, coastal, rain shadow, interior, and polar.

The subtropical Sahara is the largest hot desert at 3.5 million square miles (9 million square kilometers), but Antarctica, a polar desert covering 5 million square miles (13 million square kilometers), is the largest desert overall.


Where can I learn more about global warming?


You can read about global warming—plus watch videos, get new stories, see photo galleries, and more—in our Environment site.

For practical advice on how to lead a more environmentally sensitive lifestyle, visit our Green Guide site.

National Geographic has also published various pertinent features on global warming. You can search for "global warming" in our online index.

Your public library is a good place to look for the National Geographic magazine articles listed in the index. If you are not able to locate them there, you can order any in-print publications by emailing NGS.Single@customersvc.com.

The following government websites on global warming may also interest you:

Environmental Protection Agency
National Oceanic and Atmospheric Administration