A very small portion of the total land area is made up of islands that are not considered physical parts of continents. The ocean covers almost three-fourths of Earth. The area of the ocean is more than double the area of all the continents combined. All continents border at least one ocean. Asia, the largest continent, has the longest series of coastlines. Coastlines, however, do not indicate the actual boundaries of the continents. Continents are defined by their continental shelves.
A continental shelf is a gently sloping area that extends outward from the beach far into the ocean. A continental shelf is part of the ocean, but also part of the continent. To geographers, continents are also culturally distinct. The continents of Europe and Asia, for example, are actually part of a single, enormous piece of land called Eurasia.
But linguistically and ethnically, the areas of Asia and Europe are distinct. Because of this, most geographers divide Eurasia into Europe and Asia. An imaginary line, running from the northern Ural Mountains in Russia south to the Caspian and Black Seas, separates Europe, to the west, from Asia, to the east.
Building the Continents The Earth formed 4. The continuous smashing of space debris and the pull of gravity made the inside of Earth heat up. Eventually, the earth came to have three main layers: the core , the mantle , and the crust. The crust and the top portion of the mantle form a rigid shell around the earth that is broken up into huge sections called tectonic plates.
The heat from inside the earth causes the plates to slide around on the molten mantle. 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. Africa is centrally located in the earth with the equator in the middle of it. What makes Africa unique is the fact that it has its landmass stretching all the way from the northern temperate to the southern temperate zones.
The climate in Africa is widely tropical in nature, but the southern and northern parts have temperate climatic conditions. Africa is considered to be the cradle of mankind as the oldest fossils of Homo sapiens found till presently are from the eastern locations of the African continent. The greatest concern of Africa as a continent is the presence of a large number of diverse. Various archipelagos such as Madagascar are also part of the African continent.
It is the most populated continent on earth with an estimated human population of 4. As such, the Asian population has a significant role to play in the economy of the world. It is historically recorded that the earliest human populations of the earth were from the Asian continent. The Asian continent has densely populated settlements with some regions barely populated. The Asian continental boundaries are not well defined as there is no clear geographical demarcation between Asia and Europe.
These two continents form a big landmass which is commonly termed as Eurasia. The Asian continent is popularly known for its vast variety in terms of ethnic groups, history, economics, environments, culture, and government systems. Europe is the second smallest of all the seven continents. It is composed of the western peninsula of the massive Eurasian land surface area.
Europe is separate from Asia by the watershed divides of the Caucasus and the Ural Mountains, the Caspian Sea, the black sea, Ural River and the waterways linking the Aegean Sea and the black sea. Europe is surrounded by the Mediterranean Sea in the southern side, the Atlantic Ocean in the west, the Arctic Ocean in the northern side. Europe is primarily linked with the advent of western culture, civilization and the industrial revolution.
Australia is termed as a single country continent. It is the sixth-largest country by total land surface area and remains the smallest among the seven continents. It is also known as the island continent owing to its isolated location and small size. Measure ad performance. Select basic ads. Create a personalised ads profile. Select personalised ads. Apply market research to generate audience insights.
Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Matt Rosenberg. Geography Expert. Updated April 11, View Article Sources. Cite this Article Format. Rosenberg, Matt. The 7 Continents Ranked by Size and Population. Discover Oceania's 14 Countries by Area. An Overview of the Last Global Glaciation. Geography, Politics, and Economy of Brazil.
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