North America - Natural characteristics

North America occupies the northern portion of the landmass generally referred to as the New World, the Western Hemisphere, the Americas, or simply America (which, in many countries is considered as a single continent with North America a subcontinent). North America is the third-largest continent by area, following Asia and Africa. North America's only land connection to South America is at the Isthmus of Darian/Isthmus of Panama. The continent is delimited on the southeast by most geographers at the Darién watershed along the Colombia-Panama border, placing almost all of Panama within North America. Alternatively, some geologists physiographically locate its southern limit at the Isthmus of Tehuantepec, Mexico, with Central America extending southeastward to South America from this point. The Caribbean islands, or West Indies, are considered part of North America. The continental coastline is long and irregular. The Gulf of Mexico is the largest body of water indenting the continent, followed by Hudson Bay. Others include the Gulf of Saint Lawrence and the Gulf of California.
Sonoran Desert in Arizona
Before the Central American isthmus formed, the region had been underwater. The islands of the West Indies delineate a submerged former land bridge, which had connected North and South America via what are now Florida and Venezuela.

There are numerous islands off the continent's coasts; principally, the Arctic Archipelago, the Bahamas, Turks & Caicos, the Greater and Lesser Antilles, the Aleutian Islands (some of which are in the Eastern Hemisphere proper), the Alexander Archipelago, the many thousand islands of the British Columbia Coast, and Newfoundland. Greenland, a self-governing Danish island, and the world's largest, is on the same tectonic plate (the North American Plate) and is part of North America geographically. In a geologic sense, Bermuda is not part of the Americas, but an oceanic island that was formed on the fissure of the Mid-Atlantic Ridge over 100 million years ago (mya). The nearest landmass to it is Cape Hatteras, North Carolina. However, Bermuda is often thought of as part of North America, especially given its historical, political and cultural ties to Virginia and other parts of the continent.
Moraine Lake in Banff National Park
The vast majority of North America is on the North American Plate. Parts of western Mexico, including Baja California, and of California, including the cities of San Diego, Los Angeles, and Santa Cruz, lie on the eastern edge of the Pacific Plate, with the two plates meeting along the San Andreas fault. The southernmost portion of the continent and much of the West Indies lie on the Caribbean Plate, whereas the Juan de Fuca and Cocos plates border the North American Plate on its western frontier.

The continent can be divided into four great regions (each of which contains many subregions): the Great Plains stretching from the Gulf of Mexico to the Canadian Arctic; the geologically young, mountainous west, including the Rocky Mountains, the Great Basin, California and Alaska; the raised but relatively flat plateau of the Canadian Shield in the northeast; and the varied eastern region, which includes the Appalachian Mountains, the coastal plain along the Atlantic seaboard, and the Florida peninsula. Mexico, with its long plateaus and cordilleras, falls largely in the western region, although the eastern coastal plain does extend south along the Gulf.
Nuuk, the capital city of Greenland
The western mountains are 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 Denali in Alaska.

The U.S. Geographical Survey (USGS) states that the geographic center of North America is "6 miles [10 km] west of Balta, Pierce County, North Dakota" at about 48°10′N 100°10′W, about 24 kilometres (15 mi) from Rugby, North Dakota. The USGS further states that "No marked or monumented point has been established by any government agency as the geographic center of either the 50 states, the conterminous United States, or the North American continent." Nonetheless, there is a 4.6-metre (15 ft) field stone obelisk in Rugby claiming to mark the center. The North American continental pole of inaccessibility is located 1,650 km (1,030 mi) from the nearest coastline, between Allen and Kyle, South Dakota at 43.36°N 101.97°W.

#### Geologic history

Principal hydrological divides of Canada, the United States and Mexico
Laurentia is an ancient craton which forms the geologic core of North America; it formed between 1.5 and 1.0 billion years ago during the Proterozoic eon. The Canadian Shield is the largest exposure of this craton. From the Late Paleozoic to Early Mesozoic eras, North America was joined with the other modern-day continents as part of the supercontinent Pangaea, with Eurasia to its east. One of the results of the formation of Pangaea was the Appalachian Mountains, which formed some 480 mya, making it among the oldest mountain ranges in the world. When Pangaea began to rift around 200 mya, North America became part of Laurasia, before it separated from Eurasia as its own continent during the mid-Cretaceous period. The Rockies and other western mountain ranges began forming around this time from a period of mountain building called the Laramide orogeny, between 80 and 55 mya. The formation of the Isthmus of Panama that connected the continent to South America arguably occurred approximately 12 to 15 mya, and the Great Lakes (as well as many other northern freshwater lakes and rivers) were carved by receding glaciers about 10,000 years ago.

North America is the source of much of what humanity knows about geologic time periods. The geographic area that would later become the United States has been the source of more varieties of dinosaurs than any other modern country. According to paleontologist Peter Dodson, this is primarily due to stratigraphy, climate and geography, human resources, and history. Much of the Mesozoic Era is represented by exposed outcrops in the many arid regions of the continent. The most significant Late Jurassic dinosaur-bearing fossil deposit in North America is the Morrison Formation of the western U.S.

#### Canada

Geologic map of North America published by the U.S. Geographical Survey
Geologically, Canada is one of the oldest regions in the world, with more than half of the region consisting of Precambrian rocks that have been above sea level since the beginning of the Palaeozoic era. Canada's mineral resources are diverse and extensive. Across the Canadian Shield and in the north there are large iron, nickel, zinc, copper, gold, lead, molybdenum, and uranium reserves. Large diamond concentrations have been recently developed in the Arctic, making Canada one of the world's largest producers. Throughout the Shield, there are many mining towns extracting these minerals. The largest, and best known, is Sudbury, Ontario. Sudbury is an exception to the normal process of forming minerals in the Shield since there is significant evidence that the Sudbury Basin is an ancient meteorite impact crater. The nearby, but less known Temagami Magnetic Anomaly has striking similarities to the Sudbury Basin. Its magnetic anomalies are very similar to the Sudbury Basin, and so it could be a second metal-rich impact crater. The Shield is also covered by vast boreal forests that support an important logging industry.

#### United States

The lower 48 U.S. states can be divided into roughly five physiographic provinces:

1. The American cordillera
2. The Canadian Shield Northern portion of the upper midwestern U.S.
3. The stable platform
4. The coastal plain
5. The Appalachian orogenic belt

The geology of Alaska is typical of that of the cordillera, while the major islands of Hawaii consist of Neogene volcanics erupted over a hot spot.

North America bedrock and terrain

North American cratons and basement rocks

#### Central America

 Central America rests in the Caribbean Plate.

Central America is geologically active with volcanic eruptions and earthquakes occurring from time to time. In 1976 Guatemala was hit by a major earthquake, killing 23,000 people; Managua, the capital of Nicaragua, was devastated by earthquakes in 1931 and 1972, the last one killing about 5,000 people; three earthquakes devastated El Salvador, one in 1986 and two in 2001; one earthquake devastated northern and central Costa Rica in 2009, killing at least 34 people; in Honduras a powerful earthquake killed seven people in 2009.

Volcanic eruptions are common in the region. In 1968 the Arenal Volcano, in Costa Rica, erupted and killed 87 people. Fertile soils from weathered volcanic lavas have made it possible to sustain dense populations in agriculturally productive highland areas.

Central America has many mountain ranges; the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia, and the Cordillera de Talamanca. Between the mountain ranges lie fertile valleys that are suitable for the people; in fact, most of the population of Honduras, Costa Rica, and Guatemala live in valleys. Valleys are also suitable for the production of coffee, beans, and other crops.

### Climate

North America map of Köppen climate classification
North America is a very large continent that extends from north of the Arctic Circle to south of the Tropic of Cancer. Greenland, along with the Canadian Shield, is tundra with average temperatures ranging from 10 to 20 °C (50 to 68 °F), but central Greenland is composed of a very large ice sheet. This tundra radiates throughout Canada, but its border ends near the Rocky Mountains (but still contains Alaska) and at the end of the Canadian Shield, near the Great Lakes. Climate west of the Cascade Range is described as being temperate weather with average precipitation 20 inches (510 millimetres). Climate in coastal California is described to be Mediterranean, with average temperatures in cities like San Francisco ranging from 57 to 70 °F (14 to 21 °C) over the course of the year.

Stretching from the East Coast to eastern North Dakota, and stretching down to Kansas, is the humid continental climate featuring intense seasons, with a large amount of annual precipitation, with places like New York City averaging 50 in (1,300 mm). Starting at the southern border of the humid continental climate and stretching to the Gulf of Mexico (whilst encompassing the eastern half of Texas) is the humid subtropical climate. This area has the wettest cities in the contiguous U.S., with annual precipitation reaching 67 in (1,700 mm) in Mobile, Alabama. Stretching from the borders of the humid continental and subtropical climates, and going west to the Sierra Nevada, south to the southern tip of Durango, north to the border with tundra climate, the steppe/desert climates are the driest in the United States. Highland climates cut from north to south of the continent, where subtropical or temperate climates occur just below the tropics, as in central Mexico and Guatemala. Tropical climates appear in the island regions and in the subcontinent's bottleneck. Precipitation patterns vary across the region, and as such rainforest, monsoon, and savanna types can be found, with rains and high temperatures throughout the year. Found in countries and states bathed by the Caribbean Sea or to the south of the Gulf of Mexico and the Pacific Ocean.

### Ecology

See also: List of endangered plants in North America

Notable North American fauna include the bison, black bear, jaguar, cougar, prairie dog, turkey, pronghorn, raccoon, coyote and monarch butterfly.

Notable plants that were domesticated in North America include tobacco, maize, squash, tomato, sunflower, blueberry, avocado, cotton, chile pepper and vanilla.

References: Wikipedia