Geography of North America - Physiography

Physiography

North America may be divided into at least five major physiographic regions:

Canadian Shield

This is a geologically stable area of rock dating between 2.5 and 4 Gya that occupies most of the northeastern quadrant, including Greenland.

Appalachian Mountains

The Appalachians are an old and eroded system that formed about 300 Ma and extends from the Gaspé Peninsula to Alabama.

Atlantic Coastal Plain

The plain is a belt of lowlands widening to the south that extends from south New England to Mexico.

Interior Lowlands

The lowlands extend down the middle of the continent from the Mackenzie Valley to the Atlantic Coastal Plain, and include the Great Plains on the west and the agriculturally productive Interior Plains on the east.

North American Cordillera

The cordillera is a complex belt of mountains and associated plateaus and basins some of which were formed as recently as 100–65 Ma, during the Cretaceous. The cordillera extend from Alaska into Mexico and includes two orogenic belts — the Pacific Margin on the west and the Rocky Mountains on the east — separated by a system of intermontane plateaus and basins.

The Coastal Plain and the main belts of the North American Cordillera continue in the south in Mexico (where the Mexican Plateau, bordered by the Sierra Madre Oriental and the Sierra Madre Occidental, is considered a continuation of the intermontane system) to connect the Transverse Volcanic Range, a zone of high and active volcanic peaks south of Mexico City.

The vast majority of North America is located on the North American Plate, centered on the Laurentia craton. Parts of California and western Mexico form the partial edge of the Pacific Plate; the two plates meet along the San Andreas Fault. The southern portion of the Caribbean and parts of Central America compose the much smaller Caribbean Plate.

The western mountains have split in the middle, into the main range of the Rockies and the Coast Ranges in California, Oregon, Washington, and British Columbia with the Great Basin (a lower area containing smaller ranges and low-lying deserts) in between. The highest peak is Mount McKinley/Denali in Alaska. The geographic center of North America is approximately "6 miles west of Balta, Pierce County, North Dakota" at 48⁰ 10′north, 100⁰ 10′west, and a 15 foot (4.5 m) field stone obelisk in Rugby, North Dakota (~15 miles or 25 km away) claims to mark the center.

Three countries (Canada, the United States, and Mexico) make up most of North America's land mass; they share the continent with 34 other island countries in the Caribbean south of Mexico.