Answer 1:
Thanks for your question! To date, there is
no evidence against the existence of the
supercontinent Pangaea. In fact there is
instead a lot of evidence supporting the theory
that Pangaea assembled approximately 300 million
years ago and began to break up again around 175
million years ago. The theory of plate tectonics
explains how the continents have moved in the past
and continue to move today, and evidence of plate
tectonics helps scientists understand when and how
Pangaea formed.
Here is the evidence in support of Pangaea
There are fossils from the same species on
continents that are now very far apart. Some
examples are fossils of Lystrosaurus which
was a four-legged herbivore approximately the size
of a pig, that are found in South Africa, India,
and Antarctica. Also found in South Africa, India,
and Antarctica are fossils of the plant
Glossopteris. In Brazil and West Africa
paleontologists have found fossils of the
freshwater reptile Mesosaurus. It wouldn’t be
possible for these fossils to be on these
continents that are now very far
apart if they had not once been connected or at
least much closer together. Today, many of the
same species of plants and animals live on
continents that are far from each other, but this
is because humans have brought plants and
animals with them when they traveled overseas. 300
million years ago, the only way for a plant
or animal species to get to another part of the
world would be for it to walk, swim, or get
carried by the wind.
Geologists have found rock formations and
trends in the east coast of South America that
match with rocks in West Africa, like a giant
jigsaw puzzle. The reason these rocks match is
because they formed when the continents were
connected to one another.
When glaciers move across Earth’s surface they
leave easily identified deposits and marks and
grooves in rocks. When geologists look at
glacial deposits, they can see which direction the
ice was flowing and reconstruct the location of
the glaciers. An ice age occurred from about 326 –
267 million years ago, and the glacial deposits
from this time formed in southern South America,
southern Africa, southern India, Antarctica, and
Australia. These places are now far apart, but
when Pangaea existed the glacial areas were
connected and located near the South Pole.
Finally, the strongest evidence for the
existence of Pangaea is something called
paleomagnetism. Some rocks have minerals
inside ofthem that are magnetic, and when the
rock forms those magnetic minerals will line up
and point to the North Pole. When you use a
compass for directions (not a gps or an iPhone but
an actual compass with a needle), the needle
points to the North Pole because it is magnetic
and the needle is lining up with the Earth’s
magnetic field. For the same reason your compass
needle points north, the magnetic minerals in
rocks point north when the rock forms like tiny
geological compasses. This is called
paleomagnetism. Geologists can measure the
direction that the magnetic minerals within rocks
are pointing, and the age of the rock, and put
this together to figure out where the rock was in
relation to the North Pole when it formed. If we
do this for many rocks on many different
continents we can get a picture of how the
continents have moved through time, and we can
see that between about 300 and 175 million years
ago the continents were together in a
supercontinent called Pangaea.
So we have a lot of evidence that Pangaea
existed, and have not found any evidence that
disproves the existence of Pangaea, although there
is still a lot we don’t know yet and geologists
are still working on figuring out all the details.
When the theory
of continental drift, which is the theory that
the continents have moved positions throughout
Earth’s history, was first proposed it received a
lot of criticism because there wasn’t a good
understanding of how the continents moved across
the surface of the Earth. Today, we understand
that the continents have moved because of plate
tectonics.
The surface of the earth is made up of many
rigid “plates” that move around in relation to one
another. These plates move because they are
riding on top of part of the earth called the
asthenosphere. The asthenosphere flows very
slowly through time and drags the overriding
tectonic plates with it. Some of these plates
collide with each other, some move away from one
another, and others slide past each other. When
plates move towards each other one
plate gets subducted below the other plate and
moves into the layer of the earth we call the
mantle, where it eventually melts and gets
recycled back into the earth. In places called
mid-ocean ridges,plates are moving apart from each
other and magma rises between the two plates and
cools into new
seafloor.
When plates move past each other a large
fault forms on the earth’s surface which often
creates very large earthquakes. An example of one
of these types of plate boundaries is the San
Andreas Fault in California. The San Andreas
Fault is the boundary between the Pacific plate
and the North American plate. The continents
are part of the tectonic plates, so when the
plates move around the continents move with them.
This means that as plates have moved through time,
so have the
continents.
Although we understand a lot about how
and why tectonic plates move, there are still a
lot of things we don’t yet understand. Geologists
are still working to figure out exactly when and
how the
continents came together to form Pangaea, and also
what causes continents to start rifting apart when
supercontinents break up. Despite the questions we
still have about plate tectonics, there is
overwhelming evidence that Pangaea did exist and
it is widely accepted by scientists.
I hope this answers your question!!
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