However, the continent is usually divided into North America and South America. Central America and the Caribbean are sometimes seen as another third continent in between. This division into three parts roughly corresponds with the positions of the continental plates.
This division of America into three sections can also make sense culturally and geopolitically. Today, however, we mostly use the division of America into the North American continent including Central America, the Caribbean and all of its islands, and the South American continent with its northern border between Panama and Colombia.
This boundary, based on political borders, is a pragmatic solution. Geographically, it would also make sense to draw a border line at the Isthmus of Panama, or along the Panama Canal. Even though Africa is almost always regarded as a separate continent, there are also arguments for considering Africa , together with Eurasia , as a continuous landmass and, therefore, one single continent.
The eastern part of Egypt with the Sinai Peninsula is hence usually considered to be part of Asia. Europe is viewed as an independent continent primarily due to cultural and geopolitical reasons.
Geologically and geographically, it would make more sense to speak of a Eurasian continent instead. The Eurasian Plate extends from the east of Iceland to the south of Japan. Accordingly, the continental border between Europe and Asia is probably the most controversial. The Ural Mountains and the Ural river in the north are commonly regarded as the border between the two continents.
The Bosphorus, which runs through Istanbul, is regarded as the southern border, making the city the only one that is located on two continents. The further course of the border between the Black Sea and western Kazakhstan is particularly disputed, though. This is also of interest for mountaineers.
Today, tectonic plates continue to slowly slide around the surface, just as they have been doing for hundreds of millions of years. Geologists believe the interaction of the plates, a process called plate tectonics , contributed to the creation of continents.
Studies of rocks found in ancient areas of North America have revealed that the oldest known pieces of the continents began to form nearly four billion years ago, soon after Earth itself formed. At that time, a primitive ocean covered Earth.
Only a small fraction of the crust was made up of continental material. Scientists theorize that this material built up along the boundaries of tectonic plates during a process called subduction. During subduction, plates collide, and the edge of one plate slides beneath the edge of another.
Once melted, the rock became lighter. Called magma , it rose through the overlying plate and burst out as lava. When the lava cooled, it hardened into igneous rock. Gradually, the igneous rock built up into small volcanic islands above the surface of the ocean. Over time, these islands grew bigger, partly as the result of more lava flows and partly from the buildup of material scraped off descending plates.
When plates carrying islands subducted, the islands themselves did not descend into the mantle. Their material fused with that of islands on the neighboring plate. This made even larger landmasses—the first continents. The building of volcanic islands and continental material through plate tectonics is a process that continues today. Continental crust is much lighter than oceanic crust.
In subduction zones, where tectonic plates interact with each other, oceanic crust always subducts beneath continental crust. Oceanic crust is constantly being recycled in the mantle.
For this reason, continental crust is much, much older than oceanic crust. Wandering Continents If you could visit Earth as it was millions of years ago, it would look very different. The continents have not always been where they are today. About million years ago, most continents were scattered chunks of land lying along or south of the Equator. By about million years ago, the forces that helped form Pangaea caused the supercontinent to begin to break apart. The pieces of Pangaea that began to move apart were the beginnings of the continents that we know today.
A giant landmass that would become Europe, Asia, and North America separated from another mass that would split up into other continents. In time, Antarctica and Australia, still joined together, broke away and drifted south. The small piece of land that would become the peninsula of India broke away and for millions of years moved north as a large island. It eventually collided with Asia.
Gradually, the different landmasses moved to their present locations. The positions of the continents are always changing. North America and Europe are moving away from each other at the rate of about 2. If you could visit the planet in the future, you might find that part of the United States's state of California had separated from North America and become an island. Africa might have split in two along the Great Rift Valley. It is even possible that another supercontinent may form someday.
Continental Features The surface of the continents has changed many times because of mountain building, weathering , erosion , and build-up of sediment. Continuous, slow movement of tectonic plates also changes surface features. The rocks that form the continents have been shaped and reshaped many times.
Great mountain ranges have risen and then have been worn away. Ocean waters have flooded huge areas and then gradually dried up. Massive ice sheets have come and gone, sculpting the landscape in the process. Today, all continents have great mountain ranges, vast plains, extensive plateaus, and complex river systems. Although each is unique , all the continents share two basic features: old, geologically stable regions, and younger, somewhat more active regions.
In the younger regions, the process of mountain building has happened recently and often continues to happen. The power for mountain building, or orogeny , comes from plate tectonics. One way mountains form is through the collision of two tectonic plates. The impact creates wrinkles in the crust, just as a rug wrinkles when you push against one end of it.
The plate carrying India slowly and forcefully shoved the landmass of India into Asia, which was riding on another plate. The collision continues today, causing the Himalayas to grow taller every year. Recently formed mountains, called coastal ranges, rise near the western coasts of North America and South America. Older, more stable mountain ranges are found in the interior of continents. The Appalachians of North America and the Urals, on the border between Europe and Asia, are older mountain ranges that are not geologically active.
Even older than these ancient, eroded mountain ranges are flatter, more stable areas of the continents called cratons. Every continent has a craton. Microcontinents, like New Zealand, lack cratons. Cratons have two forms: shields and platforms.
Shields are bare rocks that may be the roots or cores of ancient mountain ranges that have completely eroded away. Platforms are cratons with sediment and sedimentary rock lying on top. The Canadian Shield makes up about a quarter of North America. For hundreds of thousands of years, sheets of ice up to 3.
The moving ice wore away material on top of ancient rock layers, exposing some of the oldest formations on Earth. When you stand on the oldest part of the Canadian Shield, you stand directly on rocks that formed more than 3.
North America North America, the third-largest continent, extends from the tiny Aleutian Islands in the northwest to the Isthmus of Panama in the south. The continent includes the enormous island of Greenland in the northeast. In the far north, the continent stretches halfway around the world, from Greenland to the Aleutians.
In between the mountain systems lie wide plains that contain deep, rich soil. Much of the soil was formed from material deposited during the most recent glacial period. This Ice Age reached its peak about 18, years ago. As glaciers retreated, streams of melted ice dropped sediment on the land, building layers of fertile soil in the plains region.
North America contains a variety of natural wonders. Landforms and all types of vegetation can be found within its boundaries. Yellowstone National Park, in the U. Despite its name, Greenland is mostly covered with ice. Its ice is a remnant of the great ice sheets that once blanketed much of the North American continent. Greenland is the only place besides Antarctica that still has an ice sheet. From the freezing Arctic to the tropical jungles of Central America , North America enjoys more climate variation than any other continent.
Parts of the Canadian province of British Columbia and the U. South America is the fourth-largest continent and extends from the sunny beaches of the Caribbean Sea to the frigid waters near the Antarctic Circle. These islands even host some Antarctic birds, such as penguins, albatrosses, and terns. Early Spanish explorers visiting the islands for the first time saw small fires dotting the land. These fires, made by indigenous people, seemed to float on the water, which is probably how the islands got their name—Tierra del Fuego means "Land of Fire.
Many active volcanoes dot the range. These volcanic areas are fueled by heat generated as a large oceanic plate, called the Nazca Plate, grinds beneath the plate carrying South America.
The central-southern area of South America has pampas , or plains. These rich areas are ideal for agriculture. The growing of wheat is a major industry in the pampas. Grazing animals, such as cattle and sheep, are also raised in the pampas region.
In volume, the Amazon is the largest river in the world. More water flows from it than from the next six largest rivers combined. Water flows more than meters 3, feet —almost a mile. The falls are so high that most of the water evaporates into mist or is blown away by wind before it reaches the ground.
Thus, according to these two views, there should only be 6 continents. There are even geographical views that prefer the presence of both a Eurasian as well as one American continent. These geographers therefore contend that there should only be 5 continents. And if you thought that would be the lowest number, think again. There are others still who are more comfortable with a 4-continent view.
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