Imagine standing on the shore of an enormous ocean, looking across the water toward a coastline that seems to stretch endlessly in both directions. Behind you is a vast continent. But something about the landscape would be strange.
You might see plants and animals that seem familiar from places thousands of miles away. Fossils of the same creatures could be found on another continent that, in our world, is separated from you by an entire ocean. Mountains on the horizon might be connected—geologically, at least—to mountains on a continent that today lies far away.
You would be living on Pangaea, a gigantic supercontinent that existed hundreds of millions of years ago.
Pangaea was not the first time Earth's continents came together, and it will not be the last. Earth's surface is constantly moving, although so slowly that a person cannot ordinarily feel it. Continents drift across the planet like enormous pieces of a gigantic puzzle.
Today, North America, South America, Europe, Africa, Asia, Australia and Antarctica are separated by oceans. But approximately 335 million years ago, those pieces began coming together into one enormous landmass.
By about 250 million years ago, they had joined into what we call Pangaea.
And then, just as slowly as it had assembled, Pangaea began to come apart.
The story of Pangaea is really the story of a restless Earth.
What Was Pangaea?
The name Pangaea comes from ancient Greek.
Pan means "all," and Gaia means "Earth."
So Pangaea essentially means "all Earth."
The name is appropriate because Pangaea brought together most of the planet's major landmasses into a single enormous supercontinent.
It was not literally all of Earth's land. There were smaller fragments and islands that were not part of the main continent. But compared with today's arrangement of continents, Pangaea was astonishingly unified.
At its greatest extent, Pangaea stretched from regions near the North Pole toward the South Pole.
It was surrounded by a gigantic ocean known as Panthalassa.
There was also a large ocean or seaway called the Tethys Ocean along part of its eastern side.
If you could somehow travel back to the time of Pangaea, you would not recognize the world map.
Africa would be near the center of the supercontinent.
South America would fit against the western side of Africa.
North America would be joined to Europe and would occupy a position considerably different from where it is today.
India would not yet be where we know it now.
Australia and Antarctica would be joined to the southern portion of the supercontinent.
And much of the world that we now know as Asia would have a very different arrangement.
The Earth would look like an entirely different planet.
The Continents Were Not Always Moving Together
It is tempting to imagine that Earth began with Pangaea and then simply broke apart.
That isn't what happened.
Pangaea was one chapter in a much older story.
Earth is approximately 4.5 billion years old, and its continents have been assembling, breaking apart and reassembling for an immense length of time.
Long before Pangaea existed, there were other enormous continental arrangements.
Scientists have identified evidence for ancient supercontinents including:
Nuna, also called Columbia
Rodinia
Gondwana
and eventually Pangaea
There is still scientific debate about some details of these very ancient supercontinents because they existed hundreds of millions or even billions of years ago.
But the general principle is well established:
The continents move.
They are not fixed permanently in one place.
The Earth's Crust Is Not One Solid Shell
This is the key to understanding Pangaea.
Earth has several layers.
At the center is the inner core, surrounded by the outer core.
Above that is the mantle, an enormous layer of hot rock.
The outermost part of Earth consists of the crust together with the uppermost rigid portion of the mantle.
This rigid outer layer is called the lithosphere.
And the lithosphere is broken into enormous pieces called tectonic plates.
Some plates contain continents.
Others consist largely of oceanic crust.
Many contain both.
These plates fit together somewhat like pieces of an enormous, irregular jigsaw puzzle.
But unlike pieces of an ordinary puzzle, Earth's pieces are constantly moving.
Why Do the Plates Move?
This is where the story becomes particularly interesting.
Deep inside Earth, temperatures are extremely high.
The mantle is solid rock, but over immense periods of time it can deform and flow very slowly.
Heat from Earth's interior drives movements within the planet.
There are several forces involved in plate movement, including processes associated with mantle convection, the sinking of dense oceanic plates into the mantle, and the formation of new crust at mid-ocean ridges.
The movements are incredibly slow by human standards.
A tectonic plate may move only a few centimeters in a year.
That doesn't sound like much.
Your fingernails can grow at roughly the same order of magnitude.
But imagine something moving several centimeters every year for millions of years.
Eventually, it travels thousands of miles.
That is how continents can change their positions so dramatically.
The Pieces That Became Pangaea
Pangaea formed when several major continental blocks collided.
One of the most important components was Gondwana.
Gondwana was itself an enormous southern supercontinent containing what would eventually become:
South America
Africa
Antarctica
Australia
India
Madagascar
and several other continental fragments.
Another major collection of land included what would become North America and parts of Europe.
Over millions of years, these continental masses moved toward one another.
Their collisions were not gentle.
When continents collide, the rocks at their edges can be compressed, folded, fractured and pushed upward.
This can create enormous mountain ranges.
In fact, some mountains that exist today are remnants of the enormous mountain-building events associated with the assembly of Pangaea.
The Appalachian Mountains Have a Remarkable Secret
If you live in or near the eastern United States, you may have seen the Appalachian Mountains.
They are ancient.
Very ancient.
And their history reaches back to the time when continents were crashing together to form Pangaea.
The Appalachians once formed part of a much larger mountain system.
When North America collided with other continental masses, enormous forces compressed Earth's crust and pushed rocks upward.
The mountains were once considerably higher and more dramatic than they are today.
Millions upon millions of years of erosion have worn them down.
Rain, rivers, ice, wind and chemical weathering have gradually removed rock from their peaks.
Yet the roots of those ancient mountains remain.
And here is the astonishing part:
Mountain belts of similar age and geological history occur across the Atlantic.
Parts of the mountains of Scotland and Scandinavia are related to the same ancient continental collisions.
In other words, rocks on opposite sides of today's Atlantic Ocean can tell a story about a time when those lands were joined.
The ocean came later.
Africa Was Near the Heart of Pangaea
Africa occupied an important central position in Pangaea.
South America was attached to its western side.
North America was farther to the northwest.
Europe and Asia were positioned differently from their modern locations.
This central position is important because Africa contains rocks and geological structures that help scientists reconstruct Pangaea.
When geologists examine rocks on different continents, they can sometimes discover that rocks separated by thousands of miles are remarkably similar.
A particular rock formation may seem to end at the coastline of one continent.
Across the ocean, another formation may begin.
Put the continents back together, however, and the formations may line up.
It is like finding two pieces of a broken plate.
The Famous Puzzle of South America and Africa
One of the most recognizable clues to continental movement is the shape of South America and Africa.
Look at a map.
The eastern coast of South America and the western coast of Africa have shapes that appear to fit together.
This was noticed long before scientists fully understood plate tectonics.
In the early twentieth century, German scientist Alfred Wegener became one of the most famous advocates of the idea that continents had moved.
In 1915, he published his major work on what he called continental drift.
Wegener proposed that the continents had once been joined together and later separated.
He even reconstructed an ancient supercontinent.
His ideas were revolutionary.
But there was a problem.
Wegener could show considerable evidence that the continents had moved.
He could not adequately explain what force moved them.
That weakness caused many scientists to reject or criticize continental drift for decades.
Eventually, however, new discoveries transformed the situation.
Fossils Provided Extraordinary Evidence
One of the strongest clues came from fossils.
Scientists discovered the same kinds of fossils on continents now separated by enormous oceans.
One particularly famous example is Mesosaurus.
Mesosaurus was a small aquatic reptile that lived roughly 280 million years ago.
Its fossils have been found in both South America and southern Africa.
That creates a puzzle.
Mesosaurus was not a creature that could simply swim across the modern Atlantic Ocean.
The Atlantic did not exist in its present form when Mesosaurus lived.
The simplest explanation is that the lands containing those fossils were once connected.
There are other examples.
Fossils of the plant Glossopteris have been found across several southern continents, including South America, Africa, India, Antarctica and Australia.
When the continents are placed in their ancient positions, the fossil distribution suddenly makes much more sense.
The fossils form a pattern.
They are telling us:
These lands were once together.
Even Ancient Glaciers Left Clues
Fossils aren't the only evidence.
Scientists also examine ancient scratches, grooves and deposits left by glaciers.
Glaciers move across landscapes, leaving distinctive marks behind.
When scientists examined ancient glacial deposits on continents that are now widely separated, something extraordinary emerged.
The evidence suggested that glaciers had once covered areas that are now in tropical or subtropical climates.
At first this seems impossible.
But move the continents back to their positions within Gondwana and Pangaea, and the puzzle becomes much easier to solve.
The glacial markings line up.
The continents had once been arranged differently.
Coal in Places That Shouldn't Have Been Tropical
There are other clues.
Coal forms under particular environmental conditions.
Much of it develops from enormous accumulations of vegetation in wet, swampy environments.
Yet coal deposits are found in parts of the world that today have cold climates.
Antarctica, for example, contains evidence of ancient forests.
That sounds almost impossible when you think about modern Antarctica.
Today, Antarctica is covered by an enormous ice sheet.
But Antarctica was not always frozen.
When it occupied a different position and Earth's climate was different, forests grew there.
Trees lived.
Plants flourished.
And eventually some of that vegetation became buried and transformed into coal.
The rocks remember the climate of a world that no longer exists.
The Climate of Pangaea
Pangaea had an unusual climate because it was so enormous.
A continent this large creates enormous interior regions far from the moderating influence of the ocean.
Coastal areas generally experience more moderate temperatures because water heats and cools more slowly than land.
But the center of Pangaea was thousands of miles from the nearest ocean.
Those interior regions could experience extreme conditions.
Scientists believe much of the interior was arid or semi-arid.
There would have been enormous deserts.
There were also forests, wetlands, coastal environments and other ecosystems.
Pangaea was not one giant desert.
It was a continent containing many different environments.
There Were No Humans
This is an important point.
There were no human beings on Pangaea.
Not even close.
Our species, Homo sapiens, appeared only around 300,000 years ago.
Pangaea existed hundreds of millions of years earlier.
Even our distant human ancestors did not exist.
The world of Pangaea belonged to creatures very different from those alive today.
There were reptiles.
Amphibians.
Insects.
Ancient plants.
Early relatives of mammals.
And eventually dinosaurs.
Pangaea and the Age of Dinosaurs
Pangaea existed during the early part of the Mesozoic Era, the great age of reptiles.
The Mesozoic is divided into three periods:
Triassic
Jurassic
Cretaceous
Pangaea existed throughout much of the Triassic and began breaking apart during the Jurassic.
This means that some of the earliest dinosaurs lived on Pangaea.
Imagine an early dinosaur walking across a landscape that would eventually become part of North America.
It might travel across land that millions of years later would be separated by an ocean from Africa or Europe.
The world was very different.
Did Animals Walk From One Continent to Another?
Yes.
And this is one of the most fascinating consequences of Pangaea.
When continents are connected, animals can spread across them without having to cross oceans.
A species living in one region can gradually expand its range.
Plants can spread.
Animals can migrate.
Predators can follow prey.
Entire ecosystems can expand across enormous areas.
But once the continents separate, populations become isolated.
This isolation can lead to evolutionary divergence.
Over millions of years, populations that were once related can become increasingly different.
This helps explain why different continents eventually developed such distinctive wildlife.
The Great Separation Begins
Pangaea did not suddenly explode apart.
There was no single day when the supercontinent broke.
Instead, it happened slowly over tens of millions of years.
Deep within Earth, tectonic forces began pulling parts of Pangaea apart.
Cracks and fractures developed.
Magma rose from below.
Volcanic activity occurred.
Eventually, new oceanic crust formed between pieces of the former supercontinent.
An ocean began opening.
That ocean was the beginning of the Atlantic Ocean.
The Birth of the Atlantic
One of the most important events in the breakup of Pangaea was the separation of North America from Africa and Europe and the separation of South America from Africa.
As the continents moved apart, molten material rose from Earth's interior.
It cooled and became new oceanic crust.
More material emerged.
The seafloor spread.
The gap became wider.
And wider.
And wider.
Over millions of years, a narrow crack became an ocean.
That is how an ocean can be born.
The Atlantic Ocean is therefore not simply a huge body of water.
Its existence is evidence of continental separation.
The Ocean Floor Is Actually Moving
This was one of the discoveries that helped finally convince scientists that continental drift was real.
During the twentieth century, scientists studied the ocean floor.
They discovered enormous underwater mountain systems called mid-ocean ridges.
The best-known is the Mid-Atlantic Ridge.
It runs for thousands of miles beneath the Atlantic Ocean.
At these ridges, new oceanic crust forms.
The seafloor gradually moves away from the ridge.
This process is called seafloor spreading.
It provided something Wegener's original theory lacked:
A mechanism for moving the continents.
Continental drift became part of the larger and much more powerful theory of plate tectonics.
Magnetic Stripes on the Ocean Floor
Another extraordinary discovery involved Earth's magnetic field.
Earth's magnetic field has reversed many times throughout geological history.
At different times in the past, magnetic north and south have effectively switched places.
When molten rock cools and becomes solid, magnetic minerals within it can preserve information about Earth's magnetic field at that moment.
Scientists discovered symmetrical magnetic patterns on either side of mid-ocean ridges.
The stripes matched.
This was powerful evidence that new seafloor was forming at the ridge and moving outward in both directions.
The ocean floor was effectively recording Earth's history like a magnetic tape.
Pangaea Was Not Finished Breaking Apart When the Atlantic Appeared
The breakup continued.
North America separated from Europe.
South America separated from Africa.
India began moving northward.
Australia and Antarctica eventually separated.
Africa began moving in relation to Europe and other regions.
The pieces continued their journeys.
And they are still moving today.
India Had an Incredible Journey
India's history is especially remarkable.
Today, India is attached to Asia.
But it was once part of Gondwana.
After breaking away, the Indian plate traveled northward.
It moved extraordinarily far and relatively quickly by geological standards.
Eventually, India collided with Asia.
The collision continues to have consequences today.
It helped create the Himalayas, the greatest mountain range on Earth.
The Himalayas are therefore part of the continuing story of continental movement.
They are not simply old mountains sitting quietly in one place.
They are the result of an ongoing collision between enormous pieces of Earth's crust.
The Himalayas Are Still Rising
The Indian and Eurasian plates continue to interact.
The Himalayas are still being affected by these tectonic forces.
At the same time, erosion is wearing the mountains down.
So there is a kind of geological contest happening:
Earth's tectonic forces push upward while erosion works downward.
Mountains are therefore not permanent structures.
Given enough time, they can rise, erode, disappear and eventually be replaced by entirely new mountain ranges elsewhere.
Australia Is Still Moving
Australia is another continent that continues its journey.
It is moving generally northward.
Over geological time, Australia will continue changing its position.
Eventually, it may collide with parts of Southeast Asia.
The map of Earth in the distant future will look very different from today's map.
Africa Is Moving Too
Africa is also changing its position.
In eastern Africa, tectonic forces are gradually pulling parts of the continent apart.
The East African Rift is one of the most dramatic examples of continental rifting occurring today.
Over a very long period of time, the region could develop into a new ocean basin.
It is a glimpse of how the Atlantic Ocean itself may have begun.
The Earth is, in a sense, showing us its own past.
Is Pangaea Completely Gone?
Yes—and no.
The supercontinent itself no longer exists.
But its pieces are still here.
North America is still here.
South America is still here.
Africa is still here.
Europe is still here.
Asia is still here.
Australia and Antarctica are still here.
They are simply in different positions.
And pieces of the ancient continents can sometimes be recognized by their rocks.
The continents are not entirely new objects that formed after Pangaea.
Much of the continental crust is incredibly old.
Some rocks are billions of years old.
The land beneath our feet can contain pieces of Earth's deep past.
How Do Scientists Know Where the Continents Used to Be?
Scientists use many different kinds of evidence.
They study:
Fossils
Identical or related fossils found on continents now separated by oceans can reveal former connections.
Rock formations
Rock layers and mineral deposits can sometimes be matched across continents.
Mountain ranges
Ancient mountain belts can continue from one modern continent into another.
Glacial markings
Ancient ice movements can reveal where continents were located.
Ancient climates
Coal, desert deposits, coral reefs and other geological evidence can indicate the climate of a region millions of years ago.
Magnetic information
Magnetism preserved in rocks can reveal their position relative to Earth's magnetic field when the rocks formed.
Seafloor spreading
The age of oceanic crust shows that new crust is continuously created and moved away from mid-ocean ridges.
Modern satellite measurements
Today, scientists can actually measure plate movement directly using extremely precise instruments.
We don't merely believe the continents move because of old fossils.
We can measure them moving.
How Fast Is North America Moving?
Tectonic plates generally move only a few centimeters per year.
That is incredibly slow.
You would not notice North America moving during your lifetime.
But geological time changes the meaning of "slow."
Suppose a continent moved only 2 centimeters every year.
In 1,000 years, that would be about 20 meters.
In one million years, it would be about 20 kilometers.
In 100 million years, it could amount to roughly 2,000 kilometers.
The movement is tiny from year to year.
It becomes enormous over geological time.
What Would Pangaea Have Looked Like?
This is where scientists must reconstruct the past.
Nobody saw Pangaea.
There are no photographs.
There are no maps drawn by people living there.
Scientists reconstruct its shape from geological evidence.
The reconstruction is remarkably compelling.
But we should remember that the exact positions of every piece are not known with perfect precision.
Scientists continue to refine their models.
The farther back in time we go, the more uncertain some details become.
That is normal in science.
A scientific reconstruction does not have to be perfect to be extraordinarily well supported.
Was Pangaea the Only Supercontinent?
No.
And this is one of the most exciting parts of the story.
Earth seems to have gone through repeated cycles of continental assembly and breakup.
A supercontinent forms.
It eventually breaks apart.
The pieces move.
They collide with other pieces.
Another supercontinent forms.
Then that supercontinent breaks apart.
This process can take hundreds of millions of years.
Scientists sometimes refer to this as the supercontinent cycle.
Pangaea was simply the most recent great supercontinent in Earth's history.
Will Another Pangaea Form?
Probably.
But not anytime soon.
Scientists have proposed several possible arrangements for Earth's continents in the distant future.
Different models have produced names such as Pangaea Ultima, Amasia, and Novopangaea.
These are not predictions with a guaranteed outcome.
They are possible scenarios based on how scientists think today's tectonic plates may continue moving.
Depending on how the oceans open and close and how the continents move, Earth could eventually develop another supercontinent.
But we're talking about hundreds of millions of years.
Human civilization will not be around to watch it happen unless something unimaginably different happens to our species.
What Would Happen to the Oceans?
When continents move, oceans can open and close.
This is difficult to imagine because we tend to think of oceans as permanent.
They aren't.
The Atlantic Ocean is relatively young in geological terms.
The Pacific is shrinking in some areas because oceanic crust is being consumed at subduction zones.
The Mediterranean is a remnant of a much larger ancient ocean system.
Entire oceans have existed and disappeared throughout Earth's history.
An ocean can be born.
An ocean can grow.
An ocean can shrink.
An ocean can eventually disappear.
The Mediterranean Has an Ancient Story
The Mediterranean Sea is partly a remnant of the ancient Tethys Ocean.
The Tethys was enormously larger than today's Mediterranean.
As Africa moved northward and interacted with Europe and Asia, the oceanic regions between them were progressively altered and closed.
The Mediterranean is therefore a kind of geological survivor.
It is a small remaining piece of a much larger ancient ocean.
Pangaea Changed Life on Earth
Continental arrangement can influence evolution.
When continents are joined, animals and plants can spread over huge areas.
When continents separate, populations become isolated.
Climate also changes as continents move.
A continent approaching a pole experiences different conditions from one located near the equator.
Mountains alter rainfall.
New oceans alter temperatures.
Changing coastlines create and destroy habitats.
Sea levels rise and fall.
All of these things affect living organisms.
So plate tectonics is not merely about rocks.
It is connected to the history of life itself.
Imagine the World 250 Million Years Ago
Imagine walking outside on Pangaea.
There are no cities.
No roads.
No airplanes.
No farms.
No electricity.
No human voices.
There are no familiar birds singing overhead.
The animal life is strange.
The plants are strange.
The atmosphere is different.
The continents beneath your feet are in unfamiliar positions.
And if you could somehow stand there and watch for a very long time, you would see almost nothing happening to the land.
The continent would appear motionless.
Yet underneath your feet, the planet would be slowly rearranging itself.
Mountains would eventually rise.
Seas would open.
Rivers would change course.
Climate zones would shift.
Species would appear and disappear.
And, eventually, the land itself would move thousands of miles.
The Most Amazing Thing About Pangaea
Perhaps the most astonishing part of Pangaea is not that it existed.
It is that we are still living with its consequences.
The shape of today's continents is the result of that ancient world and the enormous movements that followed it.
The Appalachian Mountains contain evidence of ancient continental collisions.
The Atlantic Ocean exists because Pangaea broke apart.
The Himalayas exist because India collided with Asia.
Ancient fossils found on separate continents reveal former connections.
Antarctica once had forests.
India traveled across an ancient ocean.
Australia continues moving northward.
Africa is gradually being pulled apart in the east.
And beneath the surface of the planet, the same enormous forces that shaped Pangaea are still working.
Earth has not stopped.
We Live on a Moving Planet
It is easy to think of Earth as solid and permanent.
We stand on the ground.
The ground seems still.
Mountains seem permanent.
Continents appear immovable.
But geological time reveals a very different world.
The continents are passengers riding on enormous tectonic plates.
The plates move.
The oceans move and change.
Mountains rise and erode.
Volcanoes build new land.
Earthquakes release accumulated stresses.
Continents collide.
Continents separate.
And the planet continually reshapes itself.
The movement is too slow for us to notice in ordinary life.
But over millions of years, it is powerful enough to rearrange the face of the entire planet.
Pangaea's Great Lesson
Pangaea reminds us that the Earth we know is only one moment in an extraordinarily long story.
North America has not always been where North America is now.
Africa has not always been where Africa is now.
India was once separated from Asia by an ocean.
Antarctica was once green.
The Atlantic Ocean did not always exist.
And the continents we recognize today may eventually become parts of another entirely different world map.
If you could take a map of Earth from 250 million years ago and compare it with today's map, you might think you were looking at two different planets.
But they are the same Earth.
The rocks beneath our feet connect the two worlds.
And somewhere in those rocks are the clues that allow scientists to reconstruct a vanished supercontinent—a place where most of the world's land was joined together.
Pangaea is gone.
But it is not forgotten.
Its mountains remain.
Its fossils remain.
Its rocks remain.
Its oceans have left descendants.
And the continents that once formed it are still traveling.
Slowly.
Silently.
Continuously.
Earth is still in motion.
And someday, hundreds of millions of years from now, the pieces may come together again.
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