From the birth of a supercontinent to the deadliest extinction event in the history
of our planet, this is what the Earth looked like when America used to neighbor Africa:
Number 8 Pangaea Today, the surface of our planet is mainly
formed by seven large landmasses, referred to as continents.
They are separated by oceans, such as in the case of Australia and Antarctica, or connected
by small strips of land, like North and South America or Africa and Asia.
However, about 335 million years ago, these giant land masses were all part of a single
supercontinent called Pangaea.
Unlike the present-day distribution of continental mass, most of Pangaea was in the southern
hemisphere.
In this context, the eastern United States neighbored Africa, which occupied a somewhat
central position in the supercontinent, also neighboring the Middle East, Antarctica, Europe
and South America.
The north was mostly dominated by present-day Russia and China.
The formation and subsequent separation of Pangaea, into the continents of today, took
millions of years in a process that likely to repeat as time passes.
Number 7 Formation More than 400 million years ago, a continent
called Laurentia, which included parts of North America, collided with smaller landmasses
to form Euramerica.
It then merged with a supercontinent called Gondwana, which included Australia, Africa,
South America and parts of the Indian subcontinent.
Pangaea wasn’t the first supercontinent in the history of our planet, which spans
roughly 4.5 billion years.
These gigantic land masses seem to have been involved in a cyclical process, as they form
and break away every 300 to 500 million years.
For example, a supercontinent called Nuna was formed about 2 billion years ago and,
after it separated, Rodentia emerged from the assembly of its fragments.
The main theory for what drives this cyclical process is called plate tectonics.
It states that the outermost shell of our planet, called the lithosphere, is broken
into several tectonic plates which move around the surface over an extended time period.
This is possible because the shell beneath the lithosphere, called the asthenosphere,
is less rigid and has less mechanical strength.
Over time, it behaves almost in liquid fashion.
The mantle, the layer between the core of the planet and the surface crust, plays an
essential role in this process.
Mantle convection is the slow creeping of Earth’s solid mantle as currents carry heat
from the planet’s interior to the planet’s surface.
This process of churning and circulation in the mantle is what’s believed to have led
to the formation and separation of supercontinents.
Pangaea is the latest and best understood of them.
However, scientists are still debating what forces are responsible for the movement of
tectonic plates.
The heat most likely comes from the decay of unstable elements, such as uranium, but
it still isn’t known if the entire mantle acts like a heat conveyor belt or if there
are particular pockets of heat flow.
Pangaea started breaking apart about 175 million years ago and the progressive movement of
the plates eventually lead to the present-day landmass distribution.
Number 6 Proof of Existence While the forces behind its formation are
still being debated, there’s scientific proof for the existence of Pangaea.
Fossilized remains of plants and animals from identical species have been found on continents
which are now much farther apart.
There are also matching geological trends in adjacent continents, such as on the western
coast of Africa and the eastern coast of South America.
Glacial deposits of the same size and structure have been found on separate continents, indicating
they were once under the same ice cap.
The idea of a supercontinent is also reflected by the continuity of mountain chains, like
from the Appalachian and Allegheny ranges in North America to the Variscan Mountains
in Europe and Africa.
Quiz Question Before we move on, it’s time for our quiz
question.
Which of these is often cited as evidence for the formation of Pangaea?
Is it: a.
Human Evolution b.
Sedimentary Rocks c.
Volcanoes d.
Tidal waves Let us know what you think in the comment
section below and stay tuned to find out the right answer.
Number 5 Name The recent theory of plate tectonics was built
upon a previous theory, that of the continental drift.
It states that, over time, the continents moved away from each other, that they appeared
to have “drifted” across the ocean bed.
Speculations on an ancient supercontinent had been made before, based on the manner
in which continental coastlines appeared to fit together.
However, the man often credited for the continental drift theory is German researcher Alfred Wegener,
who published his hypothesis in 1912.
He refers to the ancient supercontinent as the “Pangaea of the Carboniferous”.
The word itself is derived from the Greek “pan”, meaning all or whole, and “Gaia”
meaning Mother Earth or land.
Many refuted his theory, as Wegener hadn’t provided a mechanism to support his concept.
Later, British geologist Arthur Holmes proposed mantle convection as the active mechanism
for the continental drift.
Number 4 Ocean A single continent also means a single ocean
surrounding it.
For Pangaea, it was a hemisphere-sized superocean called Panthalassa that covered almost 70%
of the Earth’s surface.
Because of continuous tectonic plate movement, its ocean floor has disappeared entirely.
Not much is known about the marine life, but evidence suggests the presence of coral, sponges,
single-celled organisms, a species of mollusk called Ammonites and shelled animals called
Brachiopods.
Panthalassa is also known as the Proto-Pacific, or old Pacific.
That’s because from the Mesozoic to the present era, the Pacific Ocean developed from
the center of Panthalassa.
The currents of Panthalassa would have been much slower than those of today’s oceans.
There most likely wouldn’t have been such a drastic change of tides.
The superocean is believed to have been very calm with a much more even temperature.
The function of oceans changed as Pangaea started breaking apart, as did the flow of
their currents.
As they became more separated from each other, the distribution of warmth and coolness in
the oceans completely changed.
After the Americas connected, equatorial currents stopped passing from the Atlantic to the Pacific
Ocean.
This diverted more warm currents towards Europe.
There was an increase in atmospheric pressure and evaporation, which led to more rainfall.
After Australia and Antarctica separated, the Antarctic Ocean was formed.
A circumpolar current started rotating from west to east, stopping the transfer of tropical
air and water to higher latitudes.
Antarctica ultimately cooled down so much that it became frigid.
Number 3 Climate The presence of one gigantic landmass would
undoubtedly have influenced the climate.
The interior of the continent was very dry and desert-like, as it was locked behind massive
mountains, which blocked moisture or rainfall.
From coal deposits found in Europe and North America, scientists have deduced that the
parts of the Pangaea near the equator were probably a lush tropical rainforest, much
like the present-day Amazonian jungle.
These coal deposits take form through pressure and water that transform the biodegradable
material from sinking plants or animals.
In a nutshell, the climate of Pangaea was mostly arid, with recurring wet periods that
sporadically featured devastating flash floods.
Number 2 Flora and Fauna During Pangaea’s existence, of approximately
100 million years, several plants and animals flourished.
Glossopteris was a tree-like plant, which grew about 12 feet tall and had tongue-shaped
leaves.
Fossilized Glossopteris remains have been found on continents that are now at greater
distances from each other and this is considered to be proof of Pangaea’s existence.
If the continents had been in their current position, the plant would have ranged from
the equator to the polar circle.
Plants which reproduced through spores were gradually replaced by those that reproduced
through seeds.
Herbivorous animals from the Traversodontidae family roamed the supercontinent and they’re
regarded as a mammalian ancestor.
During the Permian period, 300 to 250 million years ago, beetles, cicadas and other insects
also thrived.
A marine reptile called Mesosaurus was also common.
It too serves as proof of continental drift, as its fossilized remains have been found
both in Africa and South America, two widely separated continents.
The Mesosaurus was a coastal species, so it couldn’t have crossed the ocean therefore
the two continents must have been joined together at one point.
Unfortunately for its flourishing species, Pangaea’s existence overlapped with one
of the most catastrophic events in the history of life on this planet.
Quiz Answer So which was the often-cited evidence of Pangaea’s
formation?
While a case can be made for each answer, the best-fitting is b, sedimentary rocks.
That’s because, when the rocks are formed, the magnetic minerals inside them take on
the magnetic properties of the Earth.
They show where the magnetic poles lie in relation to the rock.
Examining their orientation has revealed how the Earth’s magnetic poles have migrated
through time.
Number 1 Great Dying The Permian-Triassic extinction event, also
known as the Great Dying, is the most severe mass extinction in the history of our planet.
70% of terrestrial vertebrates and up to 96% of all marine creatures became extinct.
Unlike other similar events, not even insects were spared.
It marked the end of the Permian and the beginning of the Triassic as well as the period between
the Paleozoic and Mesozoic eras.
Nobody knows for sure what happened, but it was most likely a combination of several factors.
One of the main theories is that massive volcanic eruptions, such as that of the Siberian Traps,
gradually poisoned the land and sea.
It’s also suspected that methane-producing microbes caused a runaway greenhouse effect
in which the planet’s land and water became uninhabitable.
Another theory is that the extinction event was the result of one or more massive meteor
impact events.
If a meteor, only a few miles in diameter, collided with Earth the energy of the impact
would be equivalent to the detonation of several million nuclear weapons.
Other theories include climate change, which caused a shift in ocean circulation, or the
gradual reduction of the oxygen levels in the ocean.
Whatever the cause, it took at least 10 million years for life on Pangaea to show the first
signs of recovery.
Thanks for watching!
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