What If? Lab
What if the continents joined together again?
The land we live on moves very, very slowly. Long ago all the continents were joined into one giant land called Pangaea. What if they joined again? Let's imagine it with Olly!
Earth's outer shell is broken into plates that move a few centimeters a year. Long ago the continents were joined in one supercontinent called Pangaea, which USGS says began to break up about 225 to 200 million years ago. Imagine the continents joining together again, and follow what might change for land, climate and animals.
Plate tectonics carries continents a few centimeters a year, and over hundreds of millions of years they have gathered into supercontinents and split apart again: Rodinia, then Pangaea by about 300 million years ago. This thought experiment reassembles the continents and reasons, with help from one climate-model study, about what might follow.
The big question
The ground under our feet feels still. But it is moving, very, very slowly.
Long ago all the land was joined together. What if it joined again?
Earth's surface is broken into giant slabs of rock called plates, and they move. The continents ride along on them, so the map of the world slowly changes.
What if all the continents joined into one giant supercontinent again? In this thought experiment you can follow three paths: what a supercontinent is, what the weather might be like deep inside one, and whether animals might be able to walk anywhere.
USGS defines the theory of plate tectonics: Earth's outermost layer is fragmented into a dozen or more large and small plates moving relative to one another as they ride on hotter, more mobile material beneath.
This thought experiment reassembles the continents into one landmass and asks what might change for climate, coastlines and the spread of life. It draws on the geological record of Pangaea and on a 2023 University of Bristol climate-model study of a future supercontinent; the outcomes are reasoned ideas, not forecasts.
Explore the idea
Make a prediction
How far do the plates under the Atlantic Ocean move apart each year?
About how far does the sea floor along the Mid-Atlantic Ridge spread apart each year?
USGS gives the average spreading rate of the Mid-Atlantic Ridge as about…
- About 2.5 centimeters
- About 2.5 meters
- About 2.5 kilometers
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Established fact
The continents move very slowly, and long ago they were joined.
The continents ride on moving plates and were once joined in the supercontinent Pangaea (USGS).
Plate tectonics moves continents a few centimeters a year; they have assembled into supercontinents such as Rodinia and Pangaea (USGS).
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What the model shows
Scientists use computers to imagine the weather on a future giant land.
University of Bristol climate models show a future supercontinent, Pangea Ultima, as hot and dry.
Climate models of Pangea Ultima (Bristol, 2023) show extreme heat from continentality, a brighter Sun and higher CO₂.
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An idea scientists discuss
One giant land again is pretend for now. We imagine what might happen.
What might happen if the continents joined again is an idea built from Pangaea and from models.
Every consequence of reassembly here is reasoned from past supercontinents and models and might differ greatly in reality.
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Established fact
The sea floor in the Atlantic spreads apart a tiny bit each year.
The sea floor along the Mid-Atlantic Ridge spreads apart by about 2.5 centimeters a year, or 25 kilometers in a million years.
The Mid-Atlantic Ridge spreads at an average of about 2.5 cm/yr (25 km per million years); the East Pacific Rise exceeds 15 cm/yr (USGS).
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Established fact
Long ago all the continents were joined into one land called Pangaea.
The supercontinent Pangaea, a name meaning "all lands" in Greek, began to break up about 225 to 200 million years ago into the continents we know today.
According to the continental drift theory, Pangaea began to break up about 225–200 million years ago; Du Toit proposed it first split into Laurasia and Gondwanaland (USGS).
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Established fact
There were giant lands even before Pangaea.
Before Pangaea there was Rodinia, which formed about 1,000 million years ago. Pangaea came together by about 300 million years ago.
Nuna by about 1,750 Ma, Rodinia by about 1,000 Ma, Gondwana by 530 Ma and Pangea by about 300 Ma, whose breakup continues today (USGS, Bradley 2011).
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Established fact
When two continents push together, mountains grow.
When India crashed into Asia about 50 million years ago, the land crumpled up and made the Himalayas.
In continental collisions neither plate subducts; the India–Asia collision 50 million years ago raised the Himalayas and the Tibetan Plateau (USGS).
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An idea scientists discuss
If the continents joined again, new mountains might grow.
If the continents joined again, the oceans between them might close and new mountain ranges might rise where they meet.
A new assembly might close ocean basins and raise collisional mountain belts; which basins might close is beyond this experiment.
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Established fact
The same kinds of fossils are found in Africa and South America.
Identical fossil species are found along the coasts of Africa and South America. Wegener thought this was the strongest sign the two were once joined.
Wegener considered identical fossil species on the matching coasts of Africa and South America the most compelling evidence for their former union (USGS).
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Established fact
Even when the land was joined, plants were different in different places.
Even with the land joined in Pangaea, plants in the Triassic were quite different from region to region: northern forests were not like southern ones.
Despite the union of the landmasses, Triassic vegetation was quite provincial, with conifers, ginkgos and cycads in northern forests and Dicroidium in Gondwana at the start of the period; this decreased as the period went on (UCMP).
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An idea scientists discuss
In one giant land, animals might walk to faraway places.
In a new supercontinent, animals might be able to walk between places that oceans now keep apart, though deserts and mountains might still stop many of them.
Reassembly might connect faunas now isolated by oceans, while interior aridity and mountain belts might still limit dispersal; the balance is beyond this experiment.
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Established fact
Long ago, the middle of Pangaea was very dry.
Much of Pangaea's inland was cut off from the cooling, moist effects of the ocean, so the Triassic climate was arid, though coasts probably had seasonal monsoons.
Pangea straddled the equator; much of its interior was isolated from oceanic moisture, giving a globally arid Triassic climate with likely coastal monsoons and no polar ice caps (UCMP).
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What the model shows
Scientists used computers to imagine a giant land in the far future. It was very hot.
In University of Bristol climate models of a future supercontinent, Pangea Ultima, expected in about 250 million years, much of the land is hot and dry, and only 8 to 16 percent of it is habitable for mammals.
Farnsworth et al. (Nature Geoscience, 2023) model Pangea Ultima with the continentality effect, a Sun emitting about 2.5 percent more radiation and CO₂ possibly above 600 ppm; widespread temperatures of 40–50 °C leave 8–16 percent of land habitable for mammals.
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An idea scientists discuss
If the continents joined again, the middle might be very dry.
If the continents joined again, places far inland might get little rain and become deserts.
A new supercontinent might develop an arid interior through continentality; how dry might depend on its latitude and shape, which this experiment cannot fix.
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An idea scientists discuss
A new giant land is pretend for now. We imagine what might happen.
Any new supercontinent is expected only in the very distant future. What might happen then is an idea built from Pangaea and from scientists' models.
Every consequence of reassembly here is reasoned from the Pangaean record and a single modeling study; the real future supercontinent might differ greatly.
In our world
Today the continents are far apart, with oceans between them.
The Atlantic Ocean gets a tiny bit wider every year!
Today the continents are spread around the globe, separated by oceans. They are still moving. USGS says the sea floor along the Mid-Atlantic Ridge, an undersea mountain range, spreads apart by about 2.5 centimeters a year. That sounds slow, but it adds up to 25 kilometers in a million years.
Over the past 100 to 200 million years, this spreading has grown the Atlantic Ocean from a narrow inlet between Europe, Africa and the Americas into the vast ocean it is today.
USGS gives the average spreading rate of the Mid-Atlantic Ridge as about 2.5 cm/yr, or 25 km per million years; rates measured from ocean-floor magnetic striping range from under 2.5 cm/yr on the Arctic Ridge to over 15 cm/yr on the East Pacific Rise.
Seafloor spreading over the past 100 to 200 million years has widened the Atlantic from a small inlet into an ocean. Iceland, astride the ridge, is splitting as North America moves westward relative to Eurasia.
Imagine one giant continent
Let's pretend all the continents squeeze together into one.
The middle might be very far from the sea, and very dry. Let's find out why.
Now imagine the continents joining into one supercontinent. Oceans between them might close, and where continents push together, new mountains might rise, as the Himalayas did when India met Asia.
The middle of such a huge land might be very far from the sea, so it might be dry. Animals might be able to walk to faraway places, if deserts and mountains did not stop them. These are ideas: we reason from Pangaea and from scientists' models.
Assembling a supercontinent closes ocean basins; USGS explains that where continents converge neither subducts, so crust buckles upward, as in the India–Asia collision that raised the Himalayas and the Tibetan Plateau.
The interior might be far from oceanic moisture: UCMP describes Triassic Pangaea's inland regions as isolated from the cooling, moist effects of the ocean, giving a globally arid climate. Land routes might connect faunas, though UCMP notes Triassic vegetation stayed quite provincial despite the union. These are reasoned ideas, not predictions.
How we know the continents move
Africa and South America fit together like puzzle pieces.
The same kinds of fossils are found on both. They were once joined!
In 1912, Alfred Wegener, a German meteorologist, argued that the continents had once been joined in a supercontinent, Pangaea, a name meaning "all lands" in Greek. He noticed how well the coasts of South America and Africa fit, and that the same fossil species are found on both coasts, now far apart across the Atlantic.
Most scientists rejected his idea at first. Later, maps of the ocean floor showed new sea floor forming at mid-ocean ridges, which led to the theory of plate tectonics.
Wegener's 1912 continental drift drew on the fit of South America and Africa, identical fossil species on their matching coasts, coal from tropical plants in Antarctica, Glossopteris ferns in now-polar regions and glacial deposits in arid Africa (USGS). Its weakness was the lack of a force strong enough to move continents.
From the 1950s, ocean-floor mapping, magnetic striping, seafloor spreading and the concentration of earthquakes and volcanoes along trenches and ridges produced plate tectonics. USGS notes the nature of the forces driving the plates is still debated.
Supercontinents come and go
Pangaea was not the first giant land. There were others even longer ago.
Scientists think the continents might join again, in a very, very long time.
Pangaea was not the first supercontinent. A USGS scientist describes an earlier one called Rodinia, which formed about 1,000 million years ago and broke up in stages. Pangaea came together by about 300 million years ago. Curtin University scientists say supercontinents have formed roughly every 600 million years.
A 2023 University of Bristol study used supercomputer climate models of a future supercontinent, Pangea Ultima, expected to form in about 250 million years. In the model, it is hot and dry, with much of the land too hot for mammals.
A 2011 USGS synthesis (Bradley) sketches the sequence: Nuna by about 1,750 Ma; Rodinia by about 1,000 Ma, breaking up from about 1,000 to 520 Ma; Gondwana by 530 Ma; Pangea by about 300 Ma, whose breakup continues today. It finds that no cycle matched the ideal of complete assembly and reassembly. Curtin's Zheng-Xiang Li describes a cycle of roughly 600 million years.
The Bristol models of Pangea Ultima combine the continentality effect, a Sun emitting about 2.5 percent more radiation and higher CO₂, leaving only 8 to 16 percent of land habitable for mammals.
Amazing facts
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Iceland is slowly being pulled apart by moving plates.
Iceland sits on the Mid-Atlantic Ridge and is slowly splitting as North America moves west compared with Europe and Asia.
Iceland straddles the Mid-Atlantic Ridge and is splitting along the spreading center between the North American and Eurasian Plates (USGS).
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Long ago, people noticed that the coasts of Africa and South America fit together.
As early as 1596, the Dutch mapmaker Abraham Ortelius suggested the Americas had been torn away from Europe and Africa.
Abraham Ortelius first suggested in 1596, in Thesaurus Geographicus, that the Americas had been torn from Europe and Africa (USGS).
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Coal from old tropical plants has been found in icy Antarctica.
Coal made from tropical plants has been found in Antarctica, which Wegener took as a sign it was once closer to the equator.
Coal deposits of tropical plants in Antarctica suggested to Wegener that it once lay nearer the equator (USGS).
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An undersea mountain range runs all the way around the world.
The global mid-ocean ridge, an undersea mountain chain, is more than 50,000 kilometers long and winds around the globe like the seam on a baseball.
The mid-ocean ridge exceeds 50,000 km in length and is more than 800 km across in places, rising on average about 4,500 m above the sea floor (USGS).
Words to know
- plate
- a huge, rigid slab of solid rock that makes up part of Earth's outer layer
- plate tectonics
- the theory that Earth's outer layer is made of moving plates
- supercontinent
- a giant landmass made of most or all of Earth's continents joined together
- Pangaea
- the supercontinent that began to break apart about 225 to 200 million years ago (USGS); the name means all lands
- mid-ocean ridge
- an undersea mountain chain where plates pull apart and new sea floor forms
- continentality
- the effect of being far from the ocean, which tends to make a place drier and more extreme in temperature
Discovery challenge
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What was the giant land called when all the continents were joined?
What was the supercontinent that began to break apart about 225 to 200 million years ago?
Which supercontinent began to fragment about 225–200 million years ago, according to USGS?
- Pangaea
- Iceland
- Australia
Show the answer
Pangaea
Pangaea!
Pangaea, which eventually broke into the continents we know today.
Pangaea, first splitting into Laurasia and Gondwanaland in Du Toit's proposal (USGS).
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What does the name Pangaea mean?
What does the name Pangaea mean in Greek?
The Greek name Pangaea translates as…
- All lands
- Big ocean
- Hot desert
Show the answer
All lands
All lands!
All lands, because it held almost all of Earth's land.
"All lands" (USGS).
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What did Wegener find on the coasts of Africa and South America?
What evidence did Alfred Wegener find on the coasts of South America and Africa?
Which observation did Wegener consider the most compelling evidence that Africa and South America were once joined?
- The same kinds of fossils
- The same city buildings
- The same shipwrecks
Show the answer
The same kinds of fossils
The same kinds of fossils!
Identical fossil species, now separated by the Atlantic Ocean.
Identical fossil species along the matching coasts (USGS).
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Which mountains grew when India pushed into Asia?
Which mountain range was pushed up when India collided with Asia about 50 million years ago?
The India–Asia continental collision raised which range and plateau?
- The Himalayas
- The Andes
- The Appalachians
Show the answer
The Himalayas
The Himalayas!
The Himalayas. The land crumpled up where the two plates met.
The Himalayas and the Tibetan Plateau (USGS).
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When might the continents join into one giant land again?
In the University of Bristol study, when is the next supercontinent, Pangea Ultima, expected to form?
Farnsworth et al. (2023) model Pangea Ultima forming in about…
- In about 250 million years
- In about 250 years
- Next century
Show the answer
In about 250 million years
In about 250 million years. That is a very, very long time!
In about 250 million years.
About 250 million years from now (University of Bristol, 2023).
Experiments to try
- Watch What If? Lab What if the continents stopped moving? Earth's outer shell is broken into giant plates that creep along just a few centimeters a year. Where they meet, they build mountains and cause earthquakes and volcanoes. Imagine the plates stopped: rain, ice and wind would keep wearing the land down, but nothing would push new mountains up.
- Watch What If? Lab What if an ice age came back? About 20,000 years ago, ice sheets more than 3,000 meters thick covered much of North America, and the sea was about 125 meters lower than today. Ice ages come and go over tens of thousands of years as Earth's orbit and tilt slowly change. Imagine an ice age returning, and follow what might change.
- Watch What If? Lab What if Earth had no mountains? Mountains push moving air upward so it drops rain and snow on one side, leaving the other side dry. Many rivers begin high in the mountains, and mountains are home to many plants and animals. Imagine flattening them all, and follow what might change.
- Watch What If? Lab What if dinosaurs still lived today? Most dinosaurs died out 66 million years ago, after a huge asteroid hit Earth. One group survived: birds, which scientists count as living dinosaurs. Imagine the other dinosaurs had survived too. Where could they live, what would they eat, and how would they fit into today's world?
Explore next
- Watch What If? Lab What if the continents stopped moving? Earth's outer shell is broken into giant plates that creep along just a few centimeters a year. Where they meet, they build mountains and cause earthquakes and volcanoes. Imagine the plates stopped: rain, ice and wind would keep wearing the land down, but nothing would push new mountains up.
- Watch What If? Lab What if an ice age came back? About 20,000 years ago, ice sheets more than 3,000 meters thick covered much of North America, and the sea was about 125 meters lower than today. Ice ages come and go over tens of thousands of years as Earth's orbit and tilt slowly change. Imagine an ice age returning, and follow what might change.
- Watch What If? Lab What if Earth had no mountains? Mountains push moving air upward so it drops rain and snow on one side, leaving the other side dry. Many rivers begin high in the mountains, and mountains are home to many plants and animals. Imagine flattening them all, and follow what might change.
- Watch What If? Lab What if dinosaurs still lived today? Most dinosaurs died out 66 million years ago, after a huge asteroid hit Earth. One group survived: birds, which scientists count as living dinosaurs. Imagine the other dinosaurs had survived too. Where could they live, what would they eat, and how would they fit into today's world?
- Watch Geography Continental drift and Pangaea Hundreds of millions of years ago, almost all of Earth's land was joined in one supercontinent called Pangaea. It began to break apart about 200 million years ago, and its pieces slowly drifted into the continents we know. Alfred Wegener argued for this idea in 1912, but scientists only accepted it after discovering how the sea floor spreads.
- Watch Geography Tectonic plates Earth's hard outer shell is cracked into a dozen or so giant pieces called tectonic plates. They carry the continents and oceans and move a few centimeters a year. Where plates pull apart, push together or slide past each other, we find volcanoes, mountains and earthquakes.
- Watch Geography The seven continents A continent is one of Earth's main divisions of land. Most geographers count seven: from largest to smallest, Asia, Africa, North America, South America, Antarctica, Europe and Australia. Together they cover about 148 million square kilometers, and every one of them touches the ocean.
- Watch Try it What If? Lab What if Earth had no atmosphere? Earth's air works like a jacket: it keeps heat in and carries it around. Take the air away in our model of a sandy patch of ground on the equator, and the coldest part of the night drops from about 13 °C to about 2 °C.
For parents & teachers
What children will learn
- Earth's outer layer is made of moving plates that carry the continents a few centimeters a year.
- The continents were once joined in the supercontinent Pangaea, and earlier in Rodinia.
- Matching coastlines and fossils were early evidence that continents move.
- Thought experiments separate known facts, model results and reasoned ideas.
Recommended ages: 11 to 17 · About 15 minutes
Talk about it
- Why might the middle of a giant continent be drier than its coasts?
- Why did many scientists reject Wegener's idea at first, and what changed their minds?
- Why is it important to say that a model of the far future is not a certainty?
Try at home or in class
- Trace South America and Africa from a world map onto paper, cut them out (a grown-up can help with the scissors) and slide them together to see the fit that Ortelius and Wegener noticed (USGS, This Dynamic Earth).
- Mark 2.5 centimeters on a ruler: that is about how far the sea floor along the Mid-Atlantic Ridge spreads in a year (USGS). Work out how many years it takes to reach one meter.
Key vocabulary: plate, plate tectonics, supercontinent, Pangaea, mid-ocean ridge, continentality
Where these facts come from
- Historical perspective (This Dynamic Earth) , U.S. Geological Survey
- Developing the theory (This Dynamic Earth) , U.S. Geological Survey
- Understanding plate motions (This Dynamic Earth) , U.S. Geological Survey
- Secular trends in the geologic record and the supercontinent cycle , U.S. Geological Survey (Bradley, 2011)
- Curtin study finds billion-year superocean cycles in Earth's history , Curtin University
- The Triassic Period , University of California Museum of Paleontology
- New research reveals extreme heat likely to wipe out humans and mammals in the distant future , University of Bristol
Checked, not yet human-reviewed. Last updated October 24, 2026. Spotted a mistake? Tell us.