Alien McDonald, age 13, of Reno, Nev., for his question:
IS NORTH AMERICA THE LARGEST CONTINENT?
North America is the world's third largest continent. Largest of the seven continents is Asia followed in second place by Africa.
Asia covers almost 17 million square miles, Africa almost 12 million square miles while North America is almost 10 million. In fourth place is South America with almost 7 million square miles. Placing five, six and seven: Antarctic with about 5 million square miles, Europe with about 4 million square miles and Australia with about 3 million.
Technically, Europe is not a continent, but a peninsula of Asia. It is part of what may be called the Eurasian continent, with a total area of about 21 million square miles. This detail would give the world only six continents, but would still put North America in third place.
Major countries of North America include Canada (the second largest country in area in the world), the United States (fourth largest) and Mexico (13th largest). The continent also includes Greenland, the world's largest island, as well as the small French overseas department of Saint Pierre and Miquelon and the British dependency of Bermuda (both made up of small islands in the Atlantic Ocean).
North America is sometimes defined to include some two dozen countries in Central America and the West Indies.
North America, with about 400 million inhabitants, is only the fourth most populous continent in the world. The U.S. ranks fourth and Mexico 11th in population among the world's countries.
Canada and the U.S. have highly developed modern economies and Mexico, although less developed, contains some of the world's greatest deposits of petroleum and natural gas.
North America is roughly wedge shaped with its broadest expanse in the north.
According to a widely accepted scientific theory, almost all of North America is situated on the North American plate, an enormous platform considered one of about a dozen major units constituting the structural mosaic of the earth's crust.
It is thought that North America was once joined to present day Europe and Africa and that it began to break away about 170 million years ago, in the Jurassic period, with the process of continental drift accelerating about 96 million years ago, in the Cretaceous period.
As North America drifted west at a rate of about half an inch per year, the plate underlying the Pacific Ocean is believed to have thrust under the North American plate, thereby causing widespread folding, evident today in a series of high mountains along the east coast, resulting in the creation of mountains and offshore islands.
The Continental Divide, which mainly runs along the crest of the Rocky Mountains, splits North America into two great drainage basins. To the east of the Divide, water flows toward the Arctic Ocean, Hudson Bay, the Atlantic Ocean and the Gulf of Mexico. To the west rivers flow toward the Pacific Ocean.