Global Environment.com

North America

Third largest of the world 's continents, North America with its off-lying islands covers 9 million sq miles. From Newfoundland to Bering Strait it spans 116° longitude, almost one third of the northern hemisphere; in latitude it extends from the tropical Gulf of Mexico in the south to the high Arctic, with its northern point only 7° (500 miles) from the North Pole.

With a reputation of containing the biggest and best of everything, North America tends towards superlatives and extremes. Its highest peaks fall short of the highest in Asia and South America, but it includes the world's largest freshwater lake (Lake Superior) and greatest canyon (Grand Canyon, Arizona), its second largest bay (Hudson Bay), third longest river system (the Mississippi-Missouri) and fourth highest waterfall (Yosemite).

Topography and climate combine to provide an immense range of natural habitats across North America, from mangrove swamps and tropical forests in the south, through hot deserts, prairie, temperate and boreal forests, taiga and tundra polar deserts in the far north. North America can claim both the largest known living organisms (giant redwood cedars) and the oldest known (bristlecone pines), both found in the western USA.

Roughly one third of the continent, including the whole of the western flank, has been thrown into a spectacular complex of young mountains, valleys and plateaus - the Western Cordilleras. To the east lie much older mountains, longer-weathered and lower - the Appalachians in the south and the Laurentian Highlands in the north; these are separated from the western ranges by broad interior lowlands drained by the Mississippi-Missouri system.

The bleak northern plains, centered about Hudson Bay, rest on a shield or platform of ancient rocks that underlies most of central and eastern Canada. The Laurentian Shield, though warped and split by crustal movements, was massive enough to resist folding through the successive periods of mountain building that raised the Western Cordilleras. Planed by more than a million years of glaciation throughout the Ice Age, it is now free of permanent ice except on a few of the northern islands. Its surface remains littered with glacial debris that forms thin, waterlogged tundra or forest soils, and the once-glaciated region is fringed by a crescent of interlinked lakes and waterways, including the Great Bar Lake and the five Great Lakes.

Grand Canyon

Hudson Bay

Monument Valley