|What is the continental drift theory?|
|Question Date: 2019-01-16|
continental drift theory is a description
of how geologists thought continents moved.
It essentially postulated that the continents were
drifting across the surface of Earth.
Additionally, the continents were said to have
once been grouped together into a single
Alfred Wegener published a book on this
theory in 1915 based on similarities between
rocks and fossils found on different
continents, fossils of plants in anomalous
locations (e.g. tropical plants in frozen Norway),
and the shapes of the continents fitting
together like a jigsaw puzzle. (Wegener was
not the first to propose such a theory
though; he credited authors from as early as 1848
who put forth similar ideas.) His idea was
rejected largely because he could not propose a
The current theory for describing movement of
the crust is called
plate tectonics. This
theory evolved out of continental drift
theory, but includes a reasonable mechanism for
the movement of the plates.
Plate tectonics proposes that solid plates
of the crust "float" on a liquid-ish
mantle, and convection currents in the mantle
push the plates around.
Good question. Most people would call
"continental drift" (the idea that
continents are moving slowly), more than a
theory, since with Global Positioning Systems we
can actually measure them moving in real time.
(Most move about as fast as your fingernails
grow--around an inch or so per year.)
That the continents are moving is an idea that
been confirmed over and over again, so
scientists have LOTS of confidence in it.
Calling it a "theory" is almost insulting--like
saying "gravity" is just a theory. Scientists are
always cautious about separating facts and theory.
Some would say, that nothing in science is "a
fact" (absolutely certain, in other words),
because for an idea to be scientific it has to
have the potential to be proven wrong. So,
scientists are never 100% certain that an idea is
correct--it's much easier to tell when an idea is
Continents move because they are attached to
bigger structures called plates. The
surface of Earth is broken into 20 or so major
plates (imagine the shell of a hard-boiled egg
which has been cracked--each piece of that shell
would be called a plate). Earth's plates are made
up of continental portions and oceanic portions.
As plates move, they drag along continents with
Why do plates move? That's a tricky
question. We have some good ideas, but Earth
scientists are still debating the details.
I encourage you to read more about plate
tectonics--it's fun stuff!
Continental drift theory is the theory on
how the world’s land has drifted over a long
period of time. Alfred Wegener came up with it
in 1912. It makes sense because it explains why
animal and plant fossils that look alike
are found on different continents that are far
away from each other.
200 to 250 million years ago, there used to be
one huge supercontinent called Pangea. Over
time, due to plate tectonics, the land
separated into pieces and rotated, which gives us
the 7 continents we have today: Africa, Asia,
Europe, North America, South America, Australia,
Continental drift is the theory that over time,
continents move away from each other, thus
appearing to have "drifted" across the ocean bed.
For example, South America and Africa are
gradually moving apart. As they separate, lava
flows up in the space they left behind and then
hardens into rock, creating the mid-Atlantic
Continental drift is the theory that the
continents have moved across Earth's surface
over geologic time and used to be connected or
disconnected from where they are now. It has been
through several versions, but the one that is now
accepted as realistic was put forward in the
1960s, and ports that continents are attached to
plates in the Earth's crust that move, thereby
dragging continents with them, as a result
of convection due to the heat difference
between the Earth's interior and the surface.
Movement of continents or parts thereof creates
The theory of continental drift was proposed by
Alfred Wegener in 1912. His idea was
that all of the continents were once in contact
but drifted apart. He got this idea from
noticing that the shapes of the continents fit
together and that there are fossils of similar
plants and animals on different continents.
Most scientists didn't believe this, because
Wegener couldn't explain what would make
continents move and because it would be very
difficult for a continent to push its way through
In the 50's and 60's the theory of plate
tectonics was developed and is currently
considered the best explanation for how continents
move. The theory of plate tectonics states
that the earth has a relatively soft flowing
mantle and a crust made of hard plates. The plates
float on top of the mantle and move because of
circulation in the mantle and because of
differences in their own densities. The continents
sit on the plates and move with them. This is
different from continental drift, because the
continents don't move by themselves and don't have
to push through the sea floor.
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