Americas

The Americas consist of the continents of North America and South America, both located in Earth's Western Hemisphere. North America is the third-largest continent in the world, while South America is the fourth-largest. The southern point of North America and the northern point of South America are connected by a narrow strip of land called the Isthmus of Panama. This isthmus makes up the region of Central America.

Like all the other continents in the world, North America and South America were once part of a massive supercontinent that scientists call Pangaea. This singular landmass resulted from the drifting of Earth's tectonic plates, or the large geologic shelves of land under the planet's surface. Over hundreds of millions of years, these plates began shifting outward until Earth's seven continents reached their twenty-first-century positions.

North America and South America contain highly diverse geographic regions. Within these regions are many biomes, or communities of plants and animals, which vary by their locations in the continents' multiple climate zones. Biomes located on both continents include forests, plains, mountains, and deserts.

Background

The Americas formed from the ancient supercontinent known as Pangaea, which appeared about three hundred million years ago. This was a large landmass created by the convergence of the seven continents that exist on Earth in the twenty-first century.

Pangaea was only one of the many supercontinents that have formed on Earth over the planet's 4.5-billion-year history. Continents are likely able to move across the planet because of plate tectonics. This scientific theory suggests that the continents rest on subsurface plates of land that slide across Earth's mantle, the layer of rock below the crust.

Around two hundred million years ago, Pangaea started breaking into the smaller land portions that would become the continents. The landmass that contained South America, Africa, and Australia first separated from the mass that contained North America, Europe, and Asia. More than one hundred million years ago, South America split from Africa and began moving to its position of the twenty-first century, between the Atlantic and Pacific Oceans. Around sixty million years ago, North America broke off from Europe and Asia and started taking its position to the north of South America.

Overview

North America and South America each boast radically diverse geographies. Each continent is so large that it encompasses vastly disparate climate regions. Consequently, North America and South America are home to great biodiversity, or the range of different forms of plant and animal life.

North America is the third-largest continent on Earth, after Asia and Africa. It covers millions of square miles in Earth's Northern and Western Hemispheres. The most northwestern point of North America is the small Aleutian Islands off the coast of Alaska. The continent then extends east across Canada to the large island of Greenland. In the center of North America is the United States, while beneath that is Mexico. Extending from southern Mexico is an isthmus, or narrow strip of land, called the Isthmus of Panama. This region, known as Central America, is the southernmost point of North America. It connects southern North America to northern South America. Central America, however, is a cultural region distinct from North and South America.

North America contains several broad geographic regions. These include the mountainous West, the Great Plains in the center, the forested and mountainous East, the Arctic north, and the tropical island region of the Caribbean Sea. Western North America contains numerous mountain ranges, including the Rocky Mountains, the Sierra Madre, and the Cascades. This region is also known for its arid deserts, located in the southwestern United States and northern Mexico. These deserts include the Mojave and the Sonoran.

The Great Plains in the middle of North America are an expanse of mostly flat grasslands. They stretch from southern Canada to the southern United States. Many farmers grow crops, particularly grain, in the Great Plains. Eastern North America contains mountains, forests, wetlands, and sandy beaches. From the Appalachian Mountains near the continent's eastern coast to the wetland Everglades of Florida, the geography of eastern North America varies greatly.

The frigid Arctic region lies in northern Canada. This area comprises more than 40 percent of the Canadian landmass and consists mostly of snowy, icy islands. Finally, North America's Caribbean region, in its extreme southeast, contains thousands of tropical islands that feature rainforests, mountains, and volcanoes. Most of these areas of North America are dotted with rivers, canyons, and lakes.

South America is the world's fourth-largest continent. Its northern tip lies in the Gulf of Darién in the Caribbean Sea, and its southernmost point is the archipelago, or collection of islands, at Tierra del Fuego.

Like North America, South America is home to a wide range of geographic regions. The continent's coastal plains are arid deserts. This is because they are caught between the cold air of the oceans and the warmer air of mountains and highlands. This mixture of air produces low clouds that prevent precipitation from forming. The result is dry deserts, such as Chile's Atacama Desert, the driest region on Earth.

South America, however, also contains lush rainforests that flourish in the continent's mostly tropical climate. The Amazon rain forest in northern South America, for instance, owes its existence to the perpetually warm and humid environment of the Amazon River basin. Millions of animal species—including different types of insects, primates, and reptiles—inhabit the Amazon rainforest.

South America's third-broadest geographic region consists of mountains and highlands. The Andes Mountains near the continent's western coast extend the entire length of South America and make up the longest mountain range in the world; the range's highest peak is nearly 23,000 feet tall. The Brazilian Highlands make up South America's other high point. Located south of the Amazon River in Brazil, they feature plateaus that rise to more than 3,000 feet. Other geographic features of South America include grasslands, waterfalls, and swamps.

Bibliography

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