A continent is one of Earth’s biggest pieces of land. Most schools in the United States teach that there are seven continents. Their names are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Together they hold almost all the land on our planet, with wide oceans in between.
Why continents can be tricky
You might think everyone counts the continents the same way. They do not. Schools in the United States teach seven. Some countries teach five or six instead. They do this by joining a few continents together, like putting North America and South America into one big land called the Americas.
Here is another surprise. Antarctica is a desert, even though it is covered in ice. A desert is any place that gets very little rain or snow. Almost no snow falls in the middle of Antarctica, so it counts as a desert. It is even bigger than the hot, sandy Sahara in Africa.
One more tricky thing is the name Australia. The word Australia can mean a country and a whole continent at the same time. It is the only continent that is also one single country with the same name.
Key facts about the seven continents
There are seven continents in the model US schools teach. They are Asia, Africa, North America, South America, Antarctica, Europe, and Australia.
Asia is the largest continent. It covers about one third of all the land on Earth, and more than half of all people live there.
Australia is the smallest continent. It is so small that people sometimes call it the island continent.
Africa has the most countries. It is split into 54 different countries, more than any other continent.
Antarctica is the coldest continent. It sits at the bottom of the world, around the South Pole, and is covered in thick ice.
North America is where the United States is found. Canada and Mexico are on this continent too.
South America has the Amazon Rainforest. This is the largest rainforest in the world.
People live on six of the seven continents. Only Antarctica has no towns or cities, just scientists who visit.
Penguins live near Antarctica, and polar bears do not. Polar bears live at the other end of the world, near the North Pole.
Long ago, all the land was joined together. It formed one giant supercontinent called Pangaea before slowly breaking apart.
Common myths about the continents
Myth: Australia is the biggest continent. Australia is the smallest continent, not the biggest. The biggest one is Asia. Asia is so large that it could hold many copies of Australia inside it.
Myth: The Sahara is the largest desert on Earth. Antarctica is the largest desert, not the Sahara. The Sahara is the largest hot desert, but cold Antarctica is bigger overall. A desert is about how little rain or snow falls, not about heat.
Myth: Polar bears and penguins live together. They live at opposite ends of the world and never meet in the wild. Penguins live near the South Pole, around Antarctica. Polar bears live near the North Pole.
Myth: There are always exactly seven continents everywhere. Different countries count the continents in different ways. Some teach five or six by joining a few continents together. Seven is what most US schools teach.
Myth: The continents have always been exactly where they are now. The continents move, very slowly, a tiny bit each year. They were once joined as one big supercontinent called Pangaea, and then they drifted apart over millions of years.
Frequently asked questions about the continents
How many continents are there?
Most schools in the United States teach that there are seven continents: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Some other countries teach five or six instead, by grouping a few of them together. So the answer can change a little depending on where you live.
What is the largest continent?
Asia is the largest continent. It covers about one third of all the land on Earth. It is also home to more people than any other continent, with both China and India having over a billion people each.
What is the smallest continent?
Australia is the smallest continent. It is so much smaller than the others that people sometimes call it the island continent. One country, also named Australia, covers almost the whole thing.
Which continent has the most countries?
Africa has the most countries. It is divided into 54 of them, more than any other continent. Some of these countries are Nigeria, Egypt, Kenya, and South Africa.
Is Antarctica a continent?
Yes. Antarctica is the continent at the very bottom of the world, around the South Pole. It is the coldest continent and is covered in thick ice. It is also the only continent with no towns, only scientists who stay for a few months to study the ice and the animals.
Each of this topic’s quiz questions cites a source for the fact it tests. You can play at any level: Rookie, Curious, Sharp, or Expert.
A continent is one of Earth’s largest areas of land, set apart from the others mostly by oceans. The model taught in most US schools counts seven of them: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. They range from gigantic Asia, which holds about a third of all land, to tiny Australia, the smallest of the seven.
Why the count is not the same everywhere
The number of continents sounds like it should be a simple fact, but it changes from place to place. The reason is that the word continent has no single strict rule behind it. People decide what counts as a continent using a mix of size, the oceans around it, and long historical habit.
Most US schools teach seven continents. In much of Latin America and parts of southern Europe, students learn six instead, because they treat North America and South America as a single continent called the Americas. In Russia and Japan, students often learn a different six-continent model that joins Europe and Asia into one continent called Eurasia. Each model is reasonable in its own way.
Antarctica adds another twist. It is the coldest continent and is buried under thick ice, yet it is also the largest desert on Earth. A desert is defined by how little rain or snow it gets, not by heat. Almost no snow falls in the Antarctic interior, so the whole frozen continent counts as a desert, larger than the hot Sahara in Africa.
Key facts about the continents
Asia is the largest continent. It covers about one third of Earth’s land and holds more people than all the other continents combined.
Australia is the smallest continent. It is also the only continent that is a single country with the same name.
Europe is the second-smallest continent. It is small in area but packed with more than 40 countries.
Africa has the most countries. It is divided into 54 of them, more than any other continent.
Africa is the second-largest continent. Only Asia is bigger.
Antarctica is the coldest, windiest, and driest continent. It is also the largest desert on Earth.
North America is the third-largest continent. It includes Canada, the United States, Mexico, and the countries of Central America and the Caribbean.
The equator crosses three continents. It passes through South America, Africa, and the islands of Asia.
Mount Everest is the highest peak on any continent. It rises about 29,032 feet (8,849 m) in Asia.
The Andes are the longest mountain range on land. They run about 5,500 miles (8,900 km) down western South America.
The Seven Summits
Each continent has one mountain that stands taller than all the rest on that continent. Mountaineers call this group the Seven Summits. Climbing all seven is one of the great challenges in the sport.
The tallest of them is Mount Everest in Asia. The others are Aconcagua in South America, Denali in North America, Mount Kilimanjaro in Africa, Mount Elbrus in Europe, and Mount Vinson in Antarctica. The seventh one is debated. Some climbers pick Mount Kosciuszko on the Australian mainland, while others pick Puncak Jaya, a higher peak on the island of New Guinea in the wider region of Oceania.
Common myths about the continents
Myth: The Sahara is the largest desert in the world. Antarctica is the largest desert overall. The Sahara is the largest hot desert, but Antarctica covers a far greater area and gets even less precipitation in its interior. Deserts are ranked by dryness, not by temperature.
Myth: A wide ocean separates Europe from Asia. Europe and Asia sit on one connected stretch of land, with no ocean between them. To split them into two continents, mapmakers use a line that runs along the Ural Mountains in Russia.
Myth: Asia has the most countries. Africa has the most, with 54 countries. Asia has fewer than 50. The idea that the largest continent must also have the most countries is a common mix-up.
Myth: Australia is just a country, not a continent. Australia is both. It is the smallest of the seven continents and also a single country with the same name. The wider name Oceania is sometimes used to include Australia plus the many Pacific islands nearby.
Myth: The continents have always sat in the same places. They move very slowly, around an inch or so a year. About 300 million years ago they were joined into one supercontinent named Pangaea, which later broke apart into the continents we know today.
Frequently asked questions about the continents
How many continents are there?
It depends on where you learn geography. Most US schools teach seven continents. Some countries teach six by combining the Americas, and others teach six by combining Europe and Asia into Eurasia. A few models go as low as five. The seven-continent model is the most common in English-speaking countries.
What is the largest continent, and what is the smallest?
Asia is the largest continent, covering about a third of Earth’s land. Australia is the smallest. Asia is so much larger that it could fit many copies of Australia inside it. In between, from largest to smallest, come Africa, North America, South America, Antarctica, and Europe.
Which continent has the most countries?
Africa has the most, with 54 countries. That is more than Asia, Europe, or any other continent. Some of the largest African countries by area are Algeria, the Democratic Republic of the Congo, and Sudan.
Why is Antarctica called a desert?
Because a desert is any place that receives very little precipitation, and Antarctica’s interior gets almost none. The thick ice you picture built up slowly over hundreds of thousands of years, not from heavy modern snowfall. By area, Antarctica is the largest desert on Earth.
Were the continents ever joined together?
Yes. About 300 million years ago, Earth’s land formed a single supercontinent called Pangaea. Over millions of years, it slowly split apart, and the pieces drifted into the positions we see now. The continents are still moving today, just too slowly to notice without careful measurements.
Source notes
The size rankings, country counts, and continent models in this article come from the sources listed above, including WorldAtlas and Britannica. The largest-desert fact is documented by Live Science, and the story of Pangaea comes from the U.S. Geological Survey.
Each of this topic’s quiz questions cites a source for the fact it tests. You can play at any level: Rookie, Curious, Sharp, or Expert.
A continent is one of Earth’s principal large landmasses, conventionally distinguished by size and by separation from other landmasses, usually across water. The model taught in most US schools recognizes seven: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Ranked by area, they run from Asia, which holds about a third of Earth’s land, down to Australia, the smallest. The continents sit on slabs of relatively light continental crust that ride atop slowly moving tectonic plates.
Why the seven continents resist a simple count
The continents look like a settled list, but the number is not fixed worldwide, and the reason is built into the definition. There is no single scientific rule for what makes a landmass a continent. Geographers weigh area, separation by water, and centuries of cultural convention, and those factors do not always point to the same answer.
The seven-continent model is standard across most English-speaking countries, along with China, India, and much of Western Europe. Elsewhere, the count shifts. In Latin America and parts of southern Europe, North and South America are taught as one continent, the Americas, giving six. In Russia, Eastern Europe, and Japan, a different six-continent model joins Europe and Asia into Eurasia. A five-continent model used by the Olympic movement merges the Americas and drops uninhabited Antarctica, leaving Africa, the Americas, Asia, Europe, and Oceania, the five rings of the Olympic flag.
Europe is the clearest case of convention over geology. Europe and Asia form one unbroken landmass with no ocean and no plate boundary between them. The line that separates them is a human invention. Since the 18th century, geographers have run that boundary along the crest of the Ural Mountains in Russia, down the Ural River, and across to the Caspian and Black seas. Many geologists simply call the whole landmass Eurasia and treat Europe as a large western peninsula of Asia.
Antarctica supplies a different surprise. It is the coldest, windiest, and driest continent, buried under an ice sheet that holds most of the planet’s fresh water, yet it is classified as a desert. A desert is defined by precipitation, not temperature, and the Antarctic interior receives less than 2 inches (about 50 mm) of water-equivalent precipitation a year. By area, that makes Antarctica the largest desert on Earth, ahead of the Sahara, which is only the largest hot desert.
The seven continents by the numbers
Asia is the largest continent at about 17.2 million square miles (44.6 million km2), roughly a third of Earth’s land, and the most populous, with more than half the world’s people. It contains the highest point on land, Mount Everest, at about 29,032 feet (8,849 m).
Africa is the second-largest at about 11.7 million square miles (30.4 million km2), close to a fifth of Earth’s land. It has 54 countries, more than any other continent, and is the only continent crossed by both the equator and the prime meridian.
North America is the third-largest at about 9.5 million square miles (24.7 million km2). It comprises 23 countries, from Canada and the United States to Mexico, Central America, and the Caribbean.
South America is the fourth-largest, home to the Amazon River, the largest river by discharge, and the Andes, the longest mountain range on land at about 5,500 miles (8,900 km).
Antarctica is the fifth-largest, larger than both Europe and Australia. It is the coldest continent, the largest desert, and the only continent with no permanent population.
Europe is the second-smallest at about 3.9 million square miles (10.2 million km2), yet it holds more than 40 countries and is densely populated.
Australia is the smallest continent at about 3 million square miles (7.7 million km2). It is the only continent that is also a single country of the same name, and it rides the fastest-moving continental plate.
The Seven Summits
Every continent has a highest point, and together those seven peaks form a mountaineering goal known as the Seven Summits. The set begins with Mount Everest in Asia, the tallest mountain above sea level on Earth. The others are Aconcagua in South America at about 22,838 feet (6,961 m), Denali in North America, Mount Kilimanjaro in Africa, Mount Elbrus in Europe, and Mount Vinson in Antarctica.
The seventh summit is the subject of a long-running debate. The Bass list names Mount Kosciuszko, the highest point on the Australian mainland at about 7,310 feet (2,228 m). The Messner list instead names Puncak Jaya, also called Carstensz Pyramid, on the island of New Guinea, which at about 16,024 feet (4,884 m) is the highest peak in the wider region of Oceania. Climbers who use the continental definition of Australia pick Kosciuszko; those who use Oceania pick Puncak Jaya.
How the continents move
The continents are not fixed. They sit on tectonic plates, large rigid sections of Earth’s outer shell that drift over the hotter, slowly flowing rock beneath. Most plates move on the order of an inch or two (a few centimeters) a year, about the rate at which fingernails grow. Australia’s plate is the fastest of the continental plates, drifting north roughly 2.8 inches (7 cm) a year, fast enough that the country’s official GPS coordinates have been updated to match.
This motion has rearranged the continents many times. About 300 million years ago, the land was assembled into a single supercontinent called Pangaea. Beginning around 200 million years ago, Pangaea broke apart, first into a northern landmass, Laurasia, and a southern one, Gondwana, then into the continents we recognize today. The Atlantic Ocean opened in the gap, and it is still widening.
The continents stand above the ocean basins because of what they are made of. Continental crust is largely granite, rich in silica and relatively light, while the ocean floor is made of denser basalt. Because continental crust is both thicker and less dense, it floats higher on the mantle, which is why the continents rise above sea level rather than sinking beneath the sea.
Common myths about the continents
Myth: There are always exactly seven continents. The count depends on the model. Seven is standard in the US, but six-continent and five-continent models are taught widely elsewhere. The word continent has no strict scientific definition.
Myth: The Sahara is the largest desert on Earth. Antarctica is the largest desert. The Sahara is the largest hot desert, at about 3.6 million square miles (9.4 million km2), but Antarctica, a cold desert, is far larger by area.
Myth: Asia has the most countries because it is the biggest. Africa has the most countries, 54, despite being the second-largest continent. Size and country count are not linked.
Myth: An ocean divides Europe from Asia. The two share one continuous landmass. The conventional boundary follows the Ural Mountains and is a matter of agreement, not geography.
Myth: The continents have always been where they are. They drift slowly on tectonic plates and were joined as Pangaea about 300 million years ago. The Atlantic Ocean is still widening today.
Frequently asked questions about the continents
How many continents are there?
Seven, in the model taught across most English-speaking countries: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Other widely used models count six (combining the Americas, or combining Europe and Asia) or five (the Olympic model, which also omits Antarctica). The variation exists because continent is a convention, not a strict scientific category.
What is the largest continent, and what is the most populous?
Asia is both. It covers about 17.2 million square miles (44.6 million km2), roughly a third of Earth’s land, and is home to more than half the world’s people, including the populations of China and India. The second-largest continent is Africa, and the second most populous is also Africa.
Which continent has the most countries?
Africa, with 54 countries. That is more than Asia’s count of fewer than 50 and far more than North America’s 23. The figure of 54 is the number recognized by the United Nations and by Britannica.
Why is Antarctica considered a desert?
Because deserts are defined by low precipitation rather than by heat. The Antarctic interior receives less than 2 inches (about 50 mm) of water-equivalent precipitation a year, which puts it well inside the desert range. By area, Antarctica is the largest desert on Earth, even though it holds most of the world’s ice.
Were the continents ever a single landmass?
Yes. About 300 million years ago they were joined as the supercontinent Pangaea. Starting roughly 200 million years ago, Pangaea split into Laurasia in the north and Gondwana in the south, then into the continents of today. Plate motion that drove that breakup continues, widening the Atlantic by about an inch a year.
Source notes
Area figures, population rankings, and the country count of 54 for Africa come from Britannica and its companion entries on Asia and the general definition of a continent. The range of continent models is summarized by BBC Science Focus, and the largest-desert ranking by Live Science. The Europe-Asia boundary is described by Britannica’s Ural Mountains entry, the breakup of Pangaea by the U.S. Geological Survey, and the makeup of continental crust by Britannica’s continental crust article.
Each of this topic’s quiz questions cites a primary source for the specific fact tested. You can play at any level: Rookie, Curious, Sharp, or Expert.
A continent is a large, continuous expanse of land that stands above the ocean basins, but the term carries two different meanings that do not always agree. In the geographical sense, a continent is one of a small number of named landmasses fixed by convention, most commonly the seven of the US-taught model: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. In the geological sense, a continent is a region underlain by thick, low-density continental crust, whether or not that crust currently sits above sea level. The two definitions usually coincide. Where they diverge, as at the Europe-Asia boundary or beneath the seas around New Zealand, the idea of a continent turns out to be far less precise than the tidy list suggests.
Two definitions, one word
The geographical continents are a cultural inheritance. The division of the world into named landmasses began with the ancient Greeks, who separated Europe, Asia, and Libya (Africa), and the list grew as exploration filled in the map. There is no quantitative rule that picks out exactly seven. Greenland, an island, is smaller than Australia, the smallest continent, so size alone does not decide the matter. Separation by water fails as well, since Europe and Asia share unbroken land. What survives is convention: a continent is a landmass that tradition treats as one.
The geological definition rests on the crust. Earth’s outer shell comes in two kinds. Oceanic crust is thin, dense, basaltic rock, typically about 4 miles (7 km) thick, continuously created at mid-ocean ridges and recycled into the mantle at subduction zones within a couple of hundred million years. Continental crust is thicker, around 20 to 25 miles (30 to 40 km) on average and far thicker under mountain belts, and it is dominated by lighter, silica-rich rocks of broadly granitic composition. The density contrast, roughly 2.7 grams per cubic centimeter for continental crust against about 3.0 for oceanic crust, is the central fact. Because continental crust is both thicker and less dense, it floats higher on the mantle, an equilibrium known as isostasy, and resists being dragged down into subduction. That buoyancy is why continents persist for billions of years while ocean floor is constantly renewed.
Cratons and the age of the continents
At the core of every continent lies a craton, a block of crust that has remained tectonically stable since Precambrian time. Where a craton’s ancient basement is exposed at the surface, often as broad, low-relief terrain, it is called a shield, such as the Canadian Shield or the Baltic Shield. Cratonic crust is the oldest material on the continents. Radiometric dating places the oldest preserved rocks, including the Acasta Gneiss of northern Canada, at close to 4 billion years, and detrital zircon grains from the Jack Hills of Western Australia push the record of continental crust back to roughly 4.4 billion years, within a few hundred million years of Earth’s formation.
Cratons survive because their deep mantle roots, the cool, thick, chemically depleted keels beneath them, are less dense and more rigid than ordinary mantle and so resist destruction. This is why the interiors of continents are quiet, while the action of plate tectonics, mountain building, volcanism, and earthquakes concentrates along the younger margins. A continent, geologically, is less a single object than a long-lived collage of cratons welded together by younger mobile belts.
How many continents? The 4-to-7 models
Because the geographical definition is conventional, reasonable traditions disagree on the count, and the defensible range runs from four to seven.
Seven continents. The standard model in most English-speaking countries, China, India, Pakistan, and much of Western Europe. It treats Europe and Asia as separate and the two Americas as separate.
Six continents (combined Americas). Common in Latin America, France, Italy, Spain, Portugal, Greece, and Romania. North and South America are taught as a single continent, the Americas.
Six continents (combined Eurasia). Common in Russia, Eastern Europe, and Japan. Europe and Asia are merged into Eurasia, reflecting their shared landmass, while the Americas stay separate.
Five continents. The model behind the Olympic rings: Africa, the Americas, Asia, Europe, and Oceania. It merges the Americas and omits Antarctica as uninhabited. A different five-continent scheme merges both pairs to give Afro-Eurasia, the Americas, Antarctica, and Australia, plus Oceania in some versions.
Four continents. The most consolidated model in serious use: Afro-Eurasia, the Americas, Antarctica, and Australia. It recognizes that Africa, Europe, and Asia form one continuous landmass connected at the Isthmus of Suez.
None of these is wrong. Each draws the lines using a defensible mix of geology, water barriers, and history.
The Europe-Asia boundary
No boundary exposes the convention more plainly than the line between Europe and Asia. The two share a single slab of continental crust, the Eurasian landmass, and sit together on the Eurasian plate, so there is no geological seam to mark a border. The division is entirely a product of human geography. The Greek geographers placed the boundary at various rivers; the modern convention dates to the 18th century, when the Russian geographer Vasily Tatishchev proposed the crest of the Ural Mountains. The conventional line now follows the Urals south to the Ural River, to the Caspian Sea, along the Caucasus or the Kuma-Manych Depression, and through the Turkish Straits to the Mediterranean. Many earth scientists sidestep the issue by treating Europe as a large western peninsula of Asia and using Eurasia for the whole.
Plate tectonics and the reshaping of continents
The modern arrangement of continents is a snapshot of a process that never stops. The lithosphere, the rigid outer layer that includes the crust and the uppermost mantle, is broken into a mosaic of plates that move over the weaker, partially molten asthenosphere below. Plate motions average a couple of centimeters a year, but they vary: the Indo-Australian plate carries Australia north at about 2.8 inches (7 cm) a year, among the fastest, while some plates creep along at well under an inch.
These motions assemble and disperse supercontinents on a cycle of roughly 300 to 500 million years, the supercontinent cycle. The most recent supercontinent, Pangaea, coalesced by about 300 million years ago and held nearly all of Earth’s land in a single mass surrounded by the global Panthalassa Ocean. Beginning around 200 million years ago, in the Early Jurassic, Pangaea rifted apart. The first split produced two supercontinents separated by the Tethys seaway: Laurasia in the north, the future North America, Europe, and most of Asia, and Gondwana in the south, the future South America, Africa, Antarctica, Australia, and the Indian subcontinent. Continued rifting opened the Atlantic, which is still widening today, and carried India northward into Asia, raising the Himalayas in the collision. The continents we map are temporary; their positions, shapes, and connections are all in slow motion.
Zealandia and the limits of the list
If a continent is defined by continental crust rather than by land above water, the seven-continent list is incomplete. In 2017, a team of geologists led by Nick Mortimer argued that Zealandia, the broad expanse of continental crust beneath New Zealand, New Caledonia, and the surrounding seafloor, meets every geological test for a continent: it is built of continental crust, it is clearly elevated above the surrounding oceanic crust, it has a well-defined area, and that area is large, close to 2 million square miles (about 5 million km2). Its disqualifying feature, in the everyday sense, is that roughly 94 percent of it lies beneath the South Pacific, leaving only New Zealand and a few islands exposed. Zealandia is a fragment of Gondwana that thinned and subsided as it rifted from Australia and Antarctica. Whether it is counted as Earth’s eighth continent depends on which definition is applied, the geological or the geographical, and that is precisely the point: the two definitions can disagree, and the familiar number seven belongs to only one of them.
Common misconceptions at expert level
Misconception: A continent is any sufficiently large landmass surrounded by water. Greenland and Madagascar are large and water-bound but are not continents, while Europe is a continent despite sharing land with Asia. The category is conventional, anchored partly in geology (continental crust) and partly in history, not in a size-plus-water rule.
Misconception: Continental crust and oceanic crust differ only in thickness. They differ in composition and density as well. Continental crust is granitic and lighter, near 2.7 grams per cubic centimeter; oceanic crust is basaltic and denser, near 3.0. The density contrast, through isostasy, is what holds continents above sea level and keeps them from subducting.
Misconception: Pangaea was the only supercontinent. Pangaea is the most recent, but the supercontinent cycle has assembled and broken several earlier ones, including Rodinia and Columbia (Nuna). Pangaea is simply the one whose breakup produced the present continents and whose fragments are still drifting.
Misconception: The Europe-Asia boundary reflects a geological divide. It does not. Europe and Asia share the Eurasian plate and one continuous mass of continental crust. The Ural boundary is an 18th-century convention with no tectonic basis.
Misconception: A continent must be entirely above sea level. Geologically, continental crust can be submerged and still be continental, as Zealandia demonstrates. Continental shelves, the flooded edges of every continent, make the same point on a smaller scale.
Frequently asked questions
What is the difference between the geological and geographical definitions of a continent?
The geographical definition lists a fixed set of named landmasses chosen by convention, typically seven. The geological definition identifies regions of thick, low-density continental crust, regardless of whether they sit above water. They usually match, but the geological definition would, for example, treat Europe and Asia as one continental crustal block and could count submerged Zealandia as a continent, while the geographical definition would not.
Why does the number of continents range from four to seven?
Because no quantitative rule fixes it. Different traditions weigh land connections, water barriers, and history differently. Merging the two Americas yields six; merging Europe and Asia yields a different six; doing both, and sometimes dropping Antarctica, yields five; merging Africa, Europe, and Asia into Afro-Eurasia yields four. The seven-continent model is one convention among several.
Why do continents stand above the ocean floor?
Because of isostasy acting on a density contrast. Continental crust is thicker and less dense than oceanic crust, so it floats higher on the mantle, much as a thick, light block floats higher in water than a thin, heavy one. The same buoyancy keeps continental crust from being subducted, which is why continents endure for billions of years.
How old is the oldest continental crust?
The oldest intact rocks, such as the Acasta Gneiss in Canada, are close to 4 billion years old. Individual zircon mineral grains from Western Australia have been dated to about 4.4 billion years, showing that some continental crust existed within a few hundred million years of Earth’s formation. This ancient material is preserved in the cratons at the cores of the continents.
Is Zealandia really a continent?
Geologically, it has a strong case. It is a large, well-defined area of elevated continental crust, distinct from the oceanic crust around it. In the everyday geographical sense it is usually left off the list because about 94 percent of it is underwater. Whether you count it as the eighth continent depends on which definition you choose.
Source notes
The definition of a continent and the absence of a single strict rule are treated in Britannica’s continent entry, with the composition and density of continental crust and the principle of isostasy from the companion articles. The age and stability of cratons are documented in the craton reference. The range of continent models is summarized by BBC Science Focus, the Europe-Asia boundary by Britannica’s Ural Mountains entry, the breakup of Pangaea into Laurasia and Gondwana by New World Encyclopedia, and the case for Zealandia as a submerged continent by the Christian Science Monitor.
Each of this topic’s quiz questions cites a primary source for the specific fact tested. You can play at any level: Rookie, Curious, Sharp, or Expert.
