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Late Precambrian Supercontinent and Ice House World
This map illustrates the break-up of the supercontinent, Rodinia, which formed 1100 million years ago. The
Late Precambrian was an "Ice House" World, much like the present-day.
More Information About the Late Precambrian
The absence of fossils of hard-shelled organisms, and the paucity of reliable paleomagnetic data, make it
difficult to produce paleogeographic maps for much of the Precambrian. With available data, 650 million
years is about as far back as we can go.
The late Precambrian, however, is an especially interesting time because the continents were colliding to
form ancient supercontinents, and because the Earth was locked in a major Ice Age.
About 1100 million years ago, the supercontinent of Rodinia was assembled. Though its exact size and
configuration are not known, it appears that North America formed the core of this supercontinent. At that
time, the east coast of North America was adjacent to western South America and the west coast of North
America lay next to Australia and Antarctica.
Rodinia split into 2 halves approximately 750 million years ago, opening the Panthalassic Ocean. North
America rotated southwards towards the ice-covered South Pole. The northern half of Rodinia, composed
primarily of Antarctica, Australia, India, Arabia, and the continental fragments that would one day become
China, rotated counter-clockwise, northwards across the frigid, North Pole.
Between the two halves of Rodinia lay a third continent - the Congo craton, made up of much of north-central
Africa. It was caught in the middle as the two halves of Rodinia came crashing down on it. By the end of the
Precambrian, about 550 million years ago, the three continents collided to form a new supercontinent called
Pannotia. The mountain-building event associated with this collision is called the Pan-African orogeny.
As mentioned previously, the global climate was cold during the Late Precambrian. Evidence of glaciation is
found on nearly every continent. Why cold conditions were so widespread has puzzled geologists. Several
hypotheses, have been proposed. One explanation suggests that the Earth was titlted sideways so that the
North Pole faced towards the Sun, and the South Pole faced away from the Sun. This would have created a
situation where 1/2 of the Earth would have broiled under the Sun for 6 months, while the other 1/2 of the
Earth would have frozen solid. Though tantalizing, no mechanism can be found that would have produced
such a drastic tilt of the Earth's axis.
A second hypothesis proposes that the Earth was encircled by a rocky and icy ring, much like the rings of
Saturn and Uranus. These rings would have cast a shadow on the Earth, cooling the climate. No trace of
this ring, however, has been found.
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A third, and the most popular hypothesis, suggests that the Earth was completely frozen - oceans and all like a giant snowball. The "Snowball Earth" hypothesis also explains anomalous isotopic signatures in
overlying rocks.
All of these hypotheses were put forward before there were accurate paleogeographic maps. The mystery
of the Late Precambrian Ice House World can be better explained by the fact that during times of continental
collision and supercontinent formation the world enters a global Ice House (like the present-day). The Late
Precambrian Ice House world was very severe, because it just so happened that many continents were near
either the North Pole or the South Pole. (The occurence of ice on Australia which was near the Equator is
an interesting exception.) It should be pointed out that though much of the Earth was glaciated, there were
regions near the equator that were ice free and enjoyed warm - if not balmly climates!
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Cambrian: the beginning of the Paleozoic Era.
Animals with hard-shells appeared in great numbers for the first time during the Cambrian. The continents
were flooded by shallow seas. The supercontinent of Gondwana had just formed and was located near the
South Pole.
More Info about the Cambrian
Panotia, the supercontinent that formed at the end of the Precambrian Era, approximately 600 million years
ago, had already begun to break apart by the beginning of the Paleozoic Era. A new ocean, the Iapetus
Ocean, widened between the ancient continents of Laurentia (North America), Baltica (Northern Europe),
and Siberia. Gondwana, the supercontinent that was assembled during the Pan-African orogeny, was the
largest continent at this time, stretching from the Equator to the South Pole. During the Ordovician Period,
warm water deposits, such as limestones and salt, were found in the equatorial regions of Gondwana
(Australia, India, China, and Antarctica), while glacial deposits and ice-rafted debris occurred the south polar
areas of Gondwana (Africa and South America).
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Ancient Oceans Separate the Continents
During the Ordovician ancient oceans separated the barren continents of Laurentia, Baltica, Siberia and
Gondwana. The end of the Ordovician was one of the coldest times in Earth history. Ice covered much of
the southern region of Gondwana.
More Ordovician Maps
This map of the Early Ordovican shows:
the Iapetus Ocean at its widest
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Avalonia (England - New England) rifting away from northen Gondwana (NW Africa)
subduction of Panthalassa beneath Laurentia and Siberi
More Info about the Ordovician
Pannotia, the supercontinent that formed at the end of the Precambrian Era, approximately 600 million years
ago, had already begun to break apart by the beginning of the Paleozoic Era. A new ocean, the Iapetus
Ocean, widened between the ancient continents of Laurentia (North America), Baltica (Northern Europe),
and Siberia. Gondwana, the supercontinent that was assembled during the Pan-African orogeny, was the
largest continent at this time, stretching from the Equator to the South Pole. During the Ordovician Period,
warm water deposits, such as limestones and salt, were found in the equatorial of Gondwana (Australia,
India, China, and Antarctica), while glacial deposits and ice-rafted debris occurred the south polar areas of
Gondwana (Africa and South America).
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Continents Begin to Collide as Paleozoic Oceans Close
Laurentia collides with Baltica closing the northen branch of the Iapetus Ocean and forming the "Old Red
Sandstone" continent. Coral reefs expand and land plants begin to colonize the barren continents.
More Silurian Maps
This map for the Early Silurian shows:
beginning of closure of the Iapetus Ocean
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the collision of Avalonia with Baltica
widening of the Rheic Ocean between Baltica and Gondwana
continued subduction along northern margin of Gondwana
subduction of the Panthalassic Ocean beneath Laurentia and Siberia
By middle Paleozoic time, approximately 400 million years ago, the Iapetus Ocean had closed bringing
Laurentia and Baltica crashing together. This continental collision, preceded in many places by the
obduction of marginal island arcs, resulted in the formation of the Caledonide mountains in Scandinavia,
northern Great Britain and Greenland, and the Northern Appalachian mountains along the eastern seaboard
of North America.
It is also likely that by middle Paleozoic times, North China and South China had rifted away from the IndoAustralian margin of Gondwana, and were headed northwards across the Paleo-Tethys Ocean. Throughout
the Early and Middle Paleozoic, the expansive Panthalassic Ocean covered muchof the northern
hemisphere. Surrounding this ocean was a subduction zone, much like the modern"ring-of-fire" that
surrounds the Pacific Ocean.
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The Devonian Was the Age of Fish!
By the Devonian the early Paleozoic oceans were closing, forming a "pre-Pangea". Freshwater fish were
able to migrate from the southern hemisphere continents to North America and Europe. Forests grew for the
first time in the equatorial regions of Artic Canada.
More Devonian Maps
This map of the Early Devonian shows:
the collision of Laurentian and Baltica to form the "Old Red Sandstone Continent" , O. R. S.
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the collision of Laurentia with Gondwana (northern South America) resulting in the Acadian mts.
continued subduction of Panthalassa beneath Laurentia and Siberia
westward subduction beneath island arcs east of Baltica (Ural mountains)
More Info about the Devonian World
By middle Paleozoic time, approximately 400 million years ago, the Iapetus Ocean had closed bringing
Laurentia and Baltica crashing together. This continental collision, preceded in many places by the
obduction of marginal island arcs, resulted in the formation of the Caledonide mountains in Scandinavia,
northern Great Britain and Greenland, and the Northern Appalachian mountains along the eastern seaboard
of North America.
It is also likely that by middle Paleozoic times, North China and South China had rifted away from the IndoAustralian margin of Gondwana, and were headed northwards across the Paleo-Tethys Ocean. Throughout
the Early and Middle
Paleozoic, the expansive Panthalassic Ocean covered much of the northern hemisphere. Surrounding this
ocean was a subduction zone, much like the modern"ring-of-fire" that surrounds the Pacific Ocean.
The Devonian was the Age of Fishes. Fish evolved jaws early in the Devonian and became the top predators
by the end of this Period.
Plants took over the land and became so abundant that the first coal deposits formed in the tropical swamps
that covered much of the Canadian Arctic Islands, northern Greenland, and Scandinavia.
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During the Early Carboniferous Pangea Begins to Form.
During the Early Carboniferous the Paleozoic oceans between Euramerica and Gondwana began to close,
forming the Appalachian and Variscan mountains. An ice cap grew at the South Pole as four-legged
vertebrates evolved in the coal swamps near the Equator.
More info about the Early Carboniferous
By the end of the Paleozoic Era, most of the oceans that had opened during the breakup of Pannotia, were
consumed as the continents collided to form the supecontinent of Pangea. Centered on the Equator,
Pangea stretched from the South Pole to the North Pole, and separated the Paleo-Tethys Ocean to the east,
from the Panthalassic Ocean to the west.
During the Late Carboniferous and Early Permian the southern regions of Pangea (southern South America
and southern Africa, Antarctica, India, southern India, and Australia) were glaciated. Evidence of a north
polar ice cap in eastern Siberia during the Late Permian.
The broad Central Pangean mountain range formed an equatorial highland that during late Carboniferous
was the locus of coal production in an equatorial rainy belt. By the mid-Permian, the Central Pangean
mountain range had moved northward into drier climates and the interior of North America and Northern
Europe became desert-like as the continued uplift of the mountain range blocked moisture-laden equatorial
winds.
The term "Pangea" means "all land". Though we call the supercontinent that formed at theend of the
Paleozoic Era, "Pangea", this supercontinent probably did not include all the landmasses that existed at that
time. In the eastern hemiphere, on either side of the Paleo-Tethys Ocean, there were continents that were
separated from the supercontinent. These continents were North and South China, and a long "windshieldwiper"-shaped continent known as Cimmeria.
Cimmeria consisted of parts of Turkey, Iran, Afghanistan, Tibet, Indochina and Malaya. It appears to have
rifted away from the Indo-Australian margin of Gondwana during the LateCarboniferous - Early Permian.
Together with the Chinese continents, Cimmeria moved northwards towards Eurasia, ultimately colliding
along the southern margin of Siberia during the late Triassic Period.
It was only after the collision of these Asian fragments that all the world's landmasses were joined together in
a supercontinent deserving of the name "Pangea".
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The Late Carboniferous a Time of Great Coal Swamps
By the Late Carboniferous the continents that make up modern North America and Europe had collided with
the southern continents of Gondwana to form the western half of Pangea. Ice covered much of the southern
hemisphere and vast coal swamps formed along the equator.
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At the end of the Permian was Greatest Extinction of All Time
Vast deserts covered western Pangea during the Permian as reptiles spread across the face of the
supercontinent. 99% of all life perished during the extinction event that marked the end of the Paleozoic Era.
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At the end of the Triassic, Pangea began to rift apart.
The supercontinent of Pangea, mostly assembled by the Triassic, allowed land animals to migrate from the
South Pole to the North Pole. Life began to rediversify after the great Permo-Triassic extinction and warmwater faunas spread across Tethys.
More Info about the Triassic
Pangea was assembled piece-wise. The continental collisions that lead to the formation of the
supercontinent began in the Devonian and continued through the Late Triassic.
In a similar fashion, the supercontinent of Pangea did not rift apart all at once, but rather was subdivided into
smaller continental blocks in three main episodes. The first episode of rifting began in the middle Jurassic,
about 180 million years ago. After an episode of igneous activity along the east coast of North America and
the northwest coast of Africa, the Central Atlantic Ocean opened as North America moved to the northwest
(See Jurassic). This movement also gave rise to the Gulf of Mexico as North America moved away from
South America. At the same time, on the other side of Africa, extensive volcanic eruptions along the adjacent
margins of east Africa, Antarctica, and Madagascar heralded the formation of the western Indian Ocean.
During the Mesozoic North America and Eurasia were one landmass, sometimes called Laurasia. As the
Central Atlantic Ocean opened, Laurasia rotated clockwise, sending North America northward, and Eurasia
southward. Coals, which were abundant in eastern Asia during the early Jurassic, were replaced by deserts
and salt deposits during the Late Jurassic as Asia moved from the wet temperate belt to the dry subtropics.
This clockwise, see-saw motion of Laurasia also lead to the closure of the wide V-shaped ocean, Tethys,
that separated Laurasia from the fragmenting southern supercontinent, Gondwana.
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Early Jurassic, the Dinosaurs spread across Pangea
By the Early Jurassic, south-central Asia had assembled. A wide Tethys ocean separated the northern
continents from Gondwana. Though Pangea was intact, the first rumblings of continental break up could be
heard.
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Pangea Begins to Rift Apart
The supercontinent of Pangea began to break apart in the Middle Jurassic. In the Late Jurassic the Central
Atlantic Ocean was a narrow ocean separating Africa from eastern North America. Eastern Gondwana had
begun to separate form Western Gondwana.
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New Oceans Begin to Open
During the Cretaceous the South Atlantic Ocean opened. India separated from Madagascar and raced
northward on a collision course with Eurasia. Notice that North America was connected to Europe, and that
Australia was still joined to
Antarctica. More Information about the Cretaceous
The second phase in the breakup of Pangea began in the early Cretaceous, about 140 million years ago.
Gondwana continued to fragment as South America separated from Africa opening the South Atlantic, and
India together with Madagascar rifted away from Antarctica and the western margin of Australia opeing the
Eastern Indian Ocean. The South Atlantic did not open all at once, but rather progressively "unzipped" from
south to north. That is why the South Atlantic is wider to the south. Other important plate tectonic events
occurred during the Cretaceous Period. These include: the initiation of rifting between North America and
Europe, the counter-clockwise rotation of Iberia from France, The separation of India from Madagascar, the
derivation of Cuba and Hispaniola from the Pacific, the uplift of the Rocky mountains, and the arrival of exotic
terranes (Wrangellia, Stikinia) along the western margin of North America.
Globally, the climate during the Cretaceous Period, like the Jurassic and Triassic, was much warmer than
today. Dinosaurs and palm trees were present north of the Arctic Circle and in Antarctica and southern
Australia. Though there may have been some at the poles during the Early Cretaceous, there were no large
ice caps at anytime during the Mesozoic Era.
These mild climatic conditions were in part due to the fact shallow seaways covered the continents during
the Cretaceous. Warm water from the equatorial regions was also transported northward, warming the polar
regions. These seaways also tended to make local climates milder, much like the modern Mediterranean
Sea, which has an ameliorating effect on the climate of Europe.
Shallow seaways covered the continents because sea level was 100 - 200 meters higher than today. Higher
sea level was due, in part, to the creation of new rifts in the ocean basins that, as discussed previously in this
article, displaced water onto the continents. The Cretaceous was also a time of rapid sea-floor spreading.
Because of their broad profile, rapidly spreading mid-ocean ridges displace more water than do slow
spreading mid-ocean ridges. Consequently, during times of rapid sea-floor spreading, sea level will tend to
rise.
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The End of the Dinosaurs
The bull's eye marks the location of the Chicxulub impact site. The impact of a 10 mile wide comet caused
global climate changes that killed the dinosaurs and many other forms of life. By the Late Cretaceous the
oceans had widened, and India approached the southern margin of Asia.
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During the Early Cenozoic India began to Collide with Asia.
50 - 55 million years ago India began to collide with Asia forming the Tibetan plateau and Himalayas.
Australia, which was attached to Antarctica, began to move rapidly northward.
More Information about the Eocene
The third, and final phase in the breakup of Pangea took place during the early Cenozoic. North America and
Greenland split away from Europe, and Antarctica released Australia which like India 50 million years earlier,
moved rapidly northward on a collision course with southeast Asia. The most recent rifting events, all taking
place within the last 20 million years include: the rifting a Arabia away from Africa opening the Red Sea, the
creation of the east African Rift System, the opening of the Sea of Japan as Japan moved eastward into the
Pacific, and the northward motion of California and northern Mexico, opening of the Gulf of California.
Though several new oceans have opened during the Cenozoic, the last 66 million years of Earth history are
better characterized as a time of intense continental collision. The most significant of these collisions has
been the collision between India and Eurasia, which began about 50 million years ago. During the Late
Cretaceous, India approached Eurasia at rates of 15 - 20 cm/yr - a plate tectonic speed record. After
colliding with marginal island arcs in the Late Cretaceous, the northern part of India, Greater India, began to
be subducted beneath Eurasia raising the Tibetan Plateau. Interesting, Asia, rather than India, has sustained
most of the deformation associated with this collision. This is because India is a solid piece of continental
lithosphere riding on a plate that is primarily made up of stronger oceanic lithosphere. Asia on the other
hand, is a loosely knit collage of continental fragments. The collision zones, or sutures, between these
fragments are still warm, and hence, can be easily reactivated. As India collided with Asia, these fragments
were squeezed northwards and eastwards out of the way, along strike-slip faults that followed older sutures.
Earthquakes along these faults continue to the present-day.
The collision of India with Asia is just one of a series of continental collisions that has all but closed the
ocean great Tethys Ocean. From east to west these continent-continent collisions are: Spain with France
forming the Pyrenees mountains, Italy with France and Switzerland forming the Alps, Greece and Turkey
with the Balkan States forming the Hellenide and Dinaride mountains, Arabia with Iran forming the Zagros
mountains, India with Asia, and finally the youngest collision, Australia with Indonesia.
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The World Assumes a Modern Configuration
20 million years ago, Antarctica was coverd by ice and the northern continents were cooling rapidly. The
world has taken on a "modern" look, but notice that Florida and parts of Asia were flooded by the sea.
More Information about the Miocene
The collision of India with Asia is just one of a series of continental collisions that has all but closed the
ocean great Tethys Ocean. From east to west these continent-continent collisions are: Spain with France
forming the Pyrenees mountains, Italy with France and Switzerland forming the Alps, Greece and Turkey
with the Balkan States forming the Hellenide and Dinaride mountains, Arabia with Iran forming the Zagros
mountains, India with Asia, and finally the youngest collision, Australia with Indonesia.
This phase of continental collision has raised high mountains by horizontally compressing the continental
lithosphere. Though the continents occupy the same volume, their area has decreased slightly.
Consequently, on a global scale, the area of the ocean basins has increased slightly during the Cenozoic, at
the expense of the continents. Because the ocean basins are larger, they can hold more water. As a result,
sea level has fallen during the last 66 million years. In general, sea level is lower during times of continental
collision (early Devonian, Late Carboniferous, Permian,Triassic).
During times of low sea level the continents are emergent, land faunas flourish, migration routes between
continents open up, the climate becomes more seasonal, and probably most importantly, the global climate
tends to cool off. This is largely because land tends to reflect the Sun's energy back to space, while the
oceans absorb the Sun's energy. Also, land masses permit the growth of permanent ice sheets, which
because they are white reflect even more energy back to space. The formation of ice on the continents, of
course, lowers sea level even further, which results in more land, which cools the Earth, forming more ice,
and so on, and so on. The lesson here is: once the Earth begins to cool (or warm-up) positive feed-back
mechanisms push the Earth's climate system to greater and greater cooling (or heating). During the last half
of the Cenozoic the Earth began to cool off. Ice sheets formed first on Antarctica and then spread to the
northern hemisphere. For the last 5 million years the Earth has been in a major Ice Age. There have been
only a few times in Earth's history when it has been as cold as it has been during the last 5 million years.
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The Earth has been in an Ice House Climate for the last 30 million years
When the Earth is in its "Ice House" climate mode, there is ice at the poles. The polar ice sheet expands and
contacts because of variations in the Earth's orbit (Milankovitch cycles). The last expansion of the polar ice
sheets took place about 18,000 years ago.
The Last Ice Age
During times of low sea level the continents are emergent, land faunas flourish, migration routes between
continents open up, the climate becomes more seasonal, and probably most importantly, the global climate
tends to cool off. This is largely because land tends to reflect the Sun's energy back to space, while the
oceans absorb the Sun's energy.
Also, landmasses at te poles permit the growth of permanent ice sheets, which because they are white,
reflect even more energy back to space. The formation of ice on the continents, alsoe, lowers sea levelr,
which exposes more land, which cools the Earth, forming more ice, and so on, and so on. The lesson here
is: once the Earth begins to cool (or warm-up) positive feed-back mechanisms push the Earth's climate
system to greater and greater cooling (or warming).
During the last half of the Cenozoic the Earth began to cool off. Ice sheets formed first on Antarctica and
then spread to the northern hemisphere. For the last 5 miilion years the Earth has been in a major Ice Age.
There have been only a few times in Earth's history when it has been as cold as it has been during the last 5
million years.
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The Present-day world has well defined climatic zones.
We are entering a new phase of continental collision that will ultimately result in the formation of a new
Pangea supercontinent in the future. Global climate is warming because we are leaving an Ice Age and
because we are adding greenhouse gases to the atmosphere.
More Information about the Modern World
During times of low sea level the continents are emergent, land faunas flourish, migration routes between
continents open up, the climate becomes more seasonal, and probably most importantly, the global climate
tends to cool off. This is largely because land tends to reflect the Sun's energy back to space, while the
oceans absorb the Sun's energy. Also, land masses permit the growth of permanent ice sheets, which
because they are white reflect even more energy back to space. The formation of ice on the continents, of
course, lowers sea level even further, which results in more land, which cools the Earth, forming more ice,
and so on, and so on. The lesson here is: once the Earth begins to cool (or warm-up) positive feed-back
mechanisms push the Earth's climate system to greater and greater cooling (or heating). During the last half
of the Cenozoic the Earth began to cool off. Ice sheets formed first on Antarctica and then spread to the
northern hemisphere. For the last 5 miilion years the Earth has been in a major Ice Age. There have been
only a few times in Earth's history when it has been as cold as it has been during the last 5 million years.
During the last 150 years humankind has increased the atmospheric concentration of greenhouses gases,
principally carbon dioxide. As a result, the gloabl climate is warming. As the Earth climate warms, the polar
ice will melt and sea level will rise. This will decrease the amount of land and less energy will be reflected
back into space. This additional warming will melt more ice and the seas will continue to flood the
continents, resulting in more warming. It is likely that rapid global warming will trigger positive feedback
mechanisms that will change the Earth's climate mode from Ice House to Green House - like it was when the
dinosaurs were around. The only question is how long will it take? 100 years, 1,000 years, or 10,000 years.
We will have to wait and see.
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This is the way the World may look like 50 million years from now!
If we continue present-day plate motions the Atlantic will widen, Africa will collide with Europe closingthe
Mediterranean, Australia will collide with S.E. Asia, and California will slide northward up the coast to Alaska
More Information about the Future World: 50 Million Years from Now
Though there is no way of knowing what the future geography of the Earth will be (except maybe through our
friends at the Psychic Connection), it is possible to project current plate motions into the future and make an
educated guess. In general, the Atlantic and Indian Oceans will continue to widen until new subduction
zones bring the continents back together, forming a Future Pangea.
The world 50 million years in the future looks slightly askew. North America is rotated slightly counterclockwise; Eurasia is rotated clockwise bringing England closer to the North Pole and Siberia southward
towards warm, subtropical latitudes.
Africa will collide with Europe and Arabia closing the Mediterranean Sea and the Red Sea. A Himalayanscale mountain range will extend from Spain, across Southern Europe, through the Mideast and into Asia.
Similarly, Australia will beach itself on the doorstep of Southeast Asia and a new subduction zone encircles
Australia and extends westward across the Cenral Indian Ocean. It is interesting to note that present plate
trajectories suggest that the East African Rift will not grow into a wide ocean.
One of the most important changes in the geography of the Future, is the beginning of subduction along the
eastern coasts of North America and South America. Though the Atlantic Ocean has widened, the Puerto
Rican Trough and Scotia Arc may propogate northward and southward along the east coast of North and
South America. In time, this new westward dipping subduction zone will consume the Atlantic Ocean.
Topics to Discuss:
What's Happening in California?
How do new Subduction Zones begin?
Sea Level Changes and Global Warming in the Future.
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The Atlantic Ocean begins to Close
New subduction zones along the eastern coasts of North America and South America will begin to consume
the ocean floor separating North America from Africa. About 100 million years from now the present-day
Mid-Atlantic Ridge will be subducted and the continents will come closer together.
The World 150 Million Years in the Future
The Atlantic Ocean, 150 million years in the future, has narrowed as a result of subduction beneath the
Americas. The Indian Ocean is also smaller due to northward subduction of oceanic crust into the Central
Indian trench. Antarctica has collided along the southern margin of Australia, and the Mid-Atlantic Ridge, the
last vestige of sea floor spreading in the Atlantic Ocean, has nearly been subducted beneath eastern North
America. The rock layers that contain the remains of ancient New York City, Boston and Washington lie atop
high mountain ranges.
When the last bit of the Mid-Atlantic spreading ridge is subducted beneath the Americas, the Atlantic Ocean
will rapidly close and a new Pangea will form.
*Topics to discuss:
Subduction of Mid-Atlantic Ridge
How do you subduct a ridge?
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"Pangea Ultima" will form 250 million years in the Future
The next Pangea, "Pangea Ultima" will form as a result of the subduction of the ocean floor of the North and
South Atlantic beneath eastern North America and South America. This supercontinent will have a small
ocean basin trapped at its center.
250 Million Years in the Future: "Pangea Ultima"
The life history of an ocean basin is determined by the balance between two opposing forces: sea floor
spreading (rifting) and subduction. During the early phases of ocean formation, rifting dominates. A small
continental rift, much like the East African Rift, grows wider forming a narrow ocean, like the Red Sea. Sea
floor spreading continues to rapidly widen the ocean.
At some point in time a subduction zone forms along one of the margins of the ocean. Ocean floor is now
destroyed at about the same rate that it is created. During this period in an ocean's history, it neither
grows nor contracts, much like the modern Pacific.
Eventually the mid-ocean ridge gets too close to one of the margins and is subducted. Now the ocean is in a
period of decline. Because no new ocean floor is being created, the ocean must close.
250 million years in the future, the Atlantic and Indian oceans have closed. North America has collided with
Africa, but in a more southerly position than where it rifted. South America is wrapped around the southern
tip of Africa, with Patagonia in contact with Indonesia, enclosing a remanent of the Indian Ocean.
Antarctica is once again at the South Pole and the Pacific has grown wider, encircling half the Earth.
We call this future Pangea, "Pangea Ultima", because it is the final Pangea.
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